.gitattributes

-pystencils/_version.py export-subst
+src/pystencils/_version.py export-subst

pyproject.toml

@@ -12,7 +12,7 @@ authors = [
 ]
 license = { file = "COPYING.txt" }
 requires-python = ">=3.10"
-dependencies = ["sympy>=1.6,<=1.11.1", "numpy>=1.8.0", "appdirs", "joblib", "pyyaml"]
+dependencies = ["sympy>=1.9,<=1.12.1", "numpy>=1.8.0", "appdirs", "joblib", "pyyaml"]
 classifiers = [
     "Development Status :: 4 - Beta",
     "Framework :: Jupyter",
@@ -71,8 +71,7 @@ tests = [
 [build-system]
 requires = [
     "setuptools>=61",
-    "versioneer>=0.29",
-    "tomli; python_version < '3.11'",
+    "versioneer[toml]>=0.29",
     # 'Cython'
 ]
 build-backend = "setuptools.build_meta"

src/pystencils/__init__.py

@@ -15,7 +15,7 @@ from .config import (
     OpenMpConfig,
 )
 from .kernel_decorator import kernel, kernel_config
-from .kernelcreation import create_kernel
+from .kernelcreation import create_kernel, create_staggered_kernel
 from .backend.kernelfunction import KernelFunction
 from .slicing import make_slice
 from .spatial_coordinates import (
@@ -28,12 +28,13 @@ from .spatial_coordinates import (
     z_,
     z_staggered,
 )
-from .sympyextensions import Assignment, AssignmentCollection, AddAugmentedAssignment
-from .sympyextensions.astnodes import assignment_from_stencil
+from .assignment import Assignment, AddAugmentedAssignment, assignment_from_stencil
+from .simp import AssignmentCollection
 from .sympyextensions.typed_sympy import TypedSymbol
-from .sympyextensions.math import SymbolCreator
+from .sympyextensions import SymbolCreator
 from .datahandling import create_data_handling
 
+
 __all__ = [
     "Field",
     "FieldType",
@@ -48,6 +49,7 @@ __all__ = [
     "VectorizationConfig",
     "OpenMpConfig",
     "create_kernel",
+    "create_staggered_kernel",
     "KernelFunction",
     "Target",
     "show_code",
@@ -75,7 +77,5 @@ __all__ = [
     "stencil",
 ]
 
-from ._version import get_versions
-
-__version__ = get_versions()["version"]
-del get_versions
+from . import _version
+__version__ = _version.get_versions()['version']

src/pystencils/_version.py

@@ -5,8 +5,9 @@
 # directories (produced by setup.py build) will contain a much shorter file
 # that just contains the computed version number.
 
-# This file is released into the public domain. Generated by
-# versioneer-0.19 (https://github.com/python-versioneer/python-versioneer)
+# This file is released into the public domain.
+# Generated by versioneer-0.29
+# https://github.com/python-versioneer/python-versioneer
 
 """Git implementation of _version.py."""
 
@@ -15,9 +16,11 @@ import os
 import re
 import subprocess
 import sys
+from typing import Any, Callable, Dict, List, Optional, Tuple
+import functools
 
 
-def get_keywords():
+def get_keywords() -> Dict[str, str]:
     """Get the keywords needed to look up the version information."""
     # these strings will be replaced by git during git-archive.
     # setup.py/versioneer.py will grep for the variable names, so they must
@@ -33,8 +36,15 @@ def get_keywords():
 class VersioneerConfig:
     """Container for Versioneer configuration parameters."""
 
+    VCS: str
+    style: str
+    tag_prefix: str
+    parentdir_prefix: str
+    versionfile_source: str
+    verbose: bool
 
-def get_config():
+
+def get_config() -> VersioneerConfig:
     """Create, populate and return the VersioneerConfig() object."""
     # these strings are filled in when 'setup.py versioneer' creates
     # _version.py
@@ -43,7 +53,7 @@ def get_config():
     cfg.style = "pep440"
     cfg.tag_prefix = "release/"
     cfg.parentdir_prefix = "pystencils-"
-    cfg.versionfile_source = "pystencils/_version.py"
+    cfg.versionfile_source = "src/pystencils/_version.py"
     cfg.verbose = False
     return cfg
 
@@ -52,13 +62,13 @@ class NotThisMethod(Exception):
     """Exception raised if a method is not valid for the current scenario."""
 
 
-LONG_VERSION_PY = {}
-HANDLERS = {}
+LONG_VERSION_PY: Dict[str, str] = {}
+HANDLERS: Dict[str, Dict[str, Callable]] = {}
 
 
-def register_vcs_handler(vcs, method):  # decorator
+def register_vcs_handler(vcs: str, method: str) -> Callable:  # decorator
     """Create decorator to mark a method as the handler of a VCS."""
-    def decorate(f):
+    def decorate(f: Callable) -> Callable:
         """Store f in HANDLERS[vcs][method]."""
         if vcs not in HANDLERS:
             HANDLERS[vcs] = {}
@@ -67,22 +77,35 @@ def register_vcs_handler(vcs, method):  # decorator
     return decorate
 
 
-def run_command(commands, args, cwd=None, verbose=False, hide_stderr=False,
-                env=None):
+def run_command(
+    commands: List[str],
+    args: List[str],
+    cwd: Optional[str] = None,
+    verbose: bool = False,
+    hide_stderr: bool = False,
+    env: Optional[Dict[str, str]] = None,
+) -> Tuple[Optional[str], Optional[int]]:
     """Call the given command(s)."""
     assert isinstance(commands, list)
-    p = None
-    for c in commands:
+    process = None
+
+    popen_kwargs: Dict[str, Any] = {}
+    if sys.platform == "win32":
+        # This hides the console window if pythonw.exe is used
+        startupinfo = subprocess.STARTUPINFO()
+        startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
+        popen_kwargs["startupinfo"] = startupinfo
+
+    for command in commands:
         try:
-            dispcmd = str([c] + args)
+            dispcmd = str([command] + args)
             # remember shell=False, so use git.cmd on windows, not just git
-            p = subprocess.Popen([c] + args, cwd=cwd, env=env,
-                                 stdout=subprocess.PIPE,
-                                 stderr=(subprocess.PIPE if hide_stderr
-                                         else None))
+            process = subprocess.Popen([command] + args, cwd=cwd, env=env,
+                                       stdout=subprocess.PIPE,
+                                       stderr=(subprocess.PIPE if hide_stderr
+                                               else None), **popen_kwargs)
             break
-        except EnvironmentError:
-            e = sys.exc_info()[1]
+        except OSError as e:
             if e.errno == errno.ENOENT:
                 continue
             if verbose:
@@ -93,16 +116,20 @@ def run_command(commands, args, cwd=None, verbose=False, hide_stderr=False,
         if verbose:
             print("unable to find command, tried %s" % (commands,))
         return None, None
-    stdout = p.communicate()[0].strip().decode()
-    if p.returncode != 0:
+    stdout = process.communicate()[0].strip().decode()
+    if process.returncode != 0:
         if verbose:
             print("unable to run %s (error)" % dispcmd)
             print("stdout was %s" % stdout)
-        return None, p.returncode
-    return stdout, p.returncode
+        return None, process.returncode
+    return stdout, process.returncode
 
 
-def versions_from_parentdir(parentdir_prefix, root, verbose):
+def versions_from_parentdir(
+    parentdir_prefix: str,
+    root: str,
+    verbose: bool,
+) -> Dict[str, Any]:
     """Try to determine the version from the parent directory name.
 
     Source tarballs conventionally unpack into a directory that includes both
@@ -111,15 +138,14 @@ def versions_from_parentdir(parentdir_prefix, root, verbose):
     """
     rootdirs = []
 
-    for i in range(3):
+    for _ in range(3):
         dirname = os.path.basename(root)
         if dirname.startswith(parentdir_prefix):
             return {"version": dirname[len(parentdir_prefix):],
                     "full-revisionid": None,
                     "dirty": False, "error": None, "date": None}
-        else:
-            rootdirs.append(root)
-            root = os.path.dirname(root)  # up a level
+        rootdirs.append(root)
+        root = os.path.dirname(root)  # up a level
 
     if verbose:
         print("Tried directories %s but none started with prefix %s" %
@@ -128,39 +154,42 @@ def versions_from_parentdir(parentdir_prefix, root, verbose):
 
 
 @register_vcs_handler("git", "get_keywords")
-def git_get_keywords(versionfile_abs):
+def git_get_keywords(versionfile_abs: str) -> Dict[str, str]:
     """Extract version information from the given file."""
     # the code embedded in _version.py can just fetch the value of these
     # keywords. When used from setup.py, we don't want to import _version.py,
     # so we do it with a regexp instead. This function is not used from
     # _version.py.
-    keywords = {}
+    keywords: Dict[str, str] = {}
     try:
-        f = open(versionfile_abs, "r")
-        for line in f.readlines():
-            if line.strip().startswith("git_refnames ="):
-                mo = re.search(r'=\s*"(.*)"', line)
-                if mo:
-                    keywords["refnames"] = mo.group(1)
-            if line.strip().startswith("git_full ="):
-                mo = re.search(r'=\s*"(.*)"', line)
-                if mo:
-                    keywords["full"] = mo.group(1)
-            if line.strip().startswith("git_date ="):
-                mo = re.search(r'=\s*"(.*)"', line)
-                if mo:
-                    keywords["date"] = mo.group(1)
-        f.close()
-    except EnvironmentError:
+        with open(versionfile_abs, "r") as fobj:
+            for line in fobj:
+                if line.strip().startswith("git_refnames ="):
+                    mo = re.search(r'=\s*"(.*)"', line)
+                    if mo:
+                        keywords["refnames"] = mo.group(1)
+                if line.strip().startswith("git_full ="):
+                    mo = re.search(r'=\s*"(.*)"', line)
+                    if mo:
+                        keywords["full"] = mo.group(1)
+                if line.strip().startswith("git_date ="):
+                    mo = re.search(r'=\s*"(.*)"', line)
+                    if mo:
+                        keywords["date"] = mo.group(1)
+    except OSError:
         pass
     return keywords
 
 
 @register_vcs_handler("git", "keywords")
-def git_versions_from_keywords(keywords, tag_prefix, verbose):
+def git_versions_from_keywords(
+    keywords: Dict[str, str],
+    tag_prefix: str,
+    verbose: bool,
+) -> Dict[str, Any]:
     """Get version information from git keywords."""
-    if not keywords:
-        raise NotThisMethod("no keywords at all, weird")
+    if "refnames" not in keywords:
+        raise NotThisMethod("Short version file found")
     date = keywords.get("date")
     if date is not None:
         # Use only the last line.  Previous lines may contain GPG signature
@@ -179,11 +208,11 @@ def git_versions_from_keywords(keywords, tag_prefix, verbose):
         if verbose:
             print("keywords are unexpanded, not using")
         raise NotThisMethod("unexpanded keywords, not a git-archive tarball")
-    refs = set([r.strip() for r in refnames.strip("()").split(",")])
+    refs = {r.strip() for r in refnames.strip("()").split(",")}
     # starting in git-1.8.3, tags are listed as "tag: foo-1.0" instead of
     # just "foo-1.0". If we see a "tag: " prefix, prefer those.
     TAG = "tag: "
-    tags = set([r[len(TAG):] for r in refs if r.startswith(TAG)])
+    tags = {r[len(TAG):] for r in refs if r.startswith(TAG)}
     if not tags:
         # Either we're using git < 1.8.3, or there really are no tags. We use
         # a heuristic: assume all version tags have a digit. The old git %d
@@ -192,7 +221,7 @@ def git_versions_from_keywords(keywords, tag_prefix, verbose):
         # between branches and tags. By ignoring refnames without digits, we
         # filter out many common branch names like "release" and
         # "stabilization", as well as "HEAD" and "master".
-        tags = set([r for r in refs if re.search(r'\d', r)])
+        tags = {r for r in refs if re.search(r'\d', r)}
         if verbose:
             print("discarding '%s', no digits" % ",".join(refs - tags))
     if verbose:
@@ -201,6 +230,11 @@ def git_versions_from_keywords(keywords, tag_prefix, verbose):
         # sorting will prefer e.g. "2.0" over "2.0rc1"
         if ref.startswith(tag_prefix):
             r = ref[len(tag_prefix):]
+            # Filter out refs that exactly match prefix or that don't start
+            # with a number once the prefix is stripped (mostly a concern
+            # when prefix is '')
+            if not re.match(r'\d', r):
+                continue
             if verbose:
                 print("picking %s" % r)
             return {"version": r,
@@ -216,7 +250,12 @@ def git_versions_from_keywords(keywords, tag_prefix, verbose):
 
 
 @register_vcs_handler("git", "pieces_from_vcs")
-def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
+def git_pieces_from_vcs(
+    tag_prefix: str,
+    root: str,
+    verbose: bool,
+    runner: Callable = run_command
+) -> Dict[str, Any]:
     """Get version from 'git describe' in the root of the source tree.
 
     This only gets called if the git-archive 'subst' keywords were *not*
@@ -227,8 +266,15 @@ def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
     if sys.platform == "win32":
         GITS = ["git.cmd", "git.exe"]
 
-    out, rc = run_command(GITS, ["rev-parse", "--git-dir"], cwd=root,
-                          hide_stderr=True)
+    # GIT_DIR can interfere with correct operation of Versioneer.
+    # It may be intended to be passed to the Versioneer-versioned project,
+    # but that should not change where we get our version from.
+    env = os.environ.copy()
+    env.pop("GIT_DIR", None)
+    runner = functools.partial(runner, env=env)
+
+    _, rc = runner(GITS, ["rev-parse", "--git-dir"], cwd=root,
+                   hide_stderr=not verbose)
     if rc != 0:
         if verbose:
             print("Directory %s not under git control" % root)
@@ -236,24 +282,57 @@ def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
 
     # if there is a tag matching tag_prefix, this yields TAG-NUM-gHEX[-dirty]
     # if there isn't one, this yields HEX[-dirty] (no NUM)
-    describe_out, rc = run_command(GITS, ["describe", "--tags", "--dirty",
-                                          "--always", "--long",
-                                          "--match", "%s*" % tag_prefix],
-                                   cwd=root)
+    describe_out, rc = runner(GITS, [
+        "describe", "--tags", "--dirty", "--always", "--long",
+        "--match", f"{tag_prefix}[[:digit:]]*"
+    ], cwd=root)
     # --long was added in git-1.5.5
     if describe_out is None:
         raise NotThisMethod("'git describe' failed")
     describe_out = describe_out.strip()
-    full_out, rc = run_command(GITS, ["rev-parse", "HEAD"], cwd=root)
+    full_out, rc = runner(GITS, ["rev-parse", "HEAD"], cwd=root)
     if full_out is None:
         raise NotThisMethod("'git rev-parse' failed")
     full_out = full_out.strip()
 
-    pieces = {}
+    pieces: Dict[str, Any] = {}
     pieces["long"] = full_out
     pieces["short"] = full_out[:7]  # maybe improved later
     pieces["error"] = None
 
+    branch_name, rc = runner(GITS, ["rev-parse", "--abbrev-ref", "HEAD"],
+                             cwd=root)
+    # --abbrev-ref was added in git-1.6.3
+    if rc != 0 or branch_name is None:
+        raise NotThisMethod("'git rev-parse --abbrev-ref' returned error")
+    branch_name = branch_name.strip()
+
+    if branch_name == "HEAD":
+        # If we aren't exactly on a branch, pick a branch which represents
+        # the current commit. If all else fails, we are on a branchless
+        # commit.
+        branches, rc = runner(GITS, ["branch", "--contains"], cwd=root)
+        # --contains was added in git-1.5.4
+        if rc != 0 or branches is None:
+            raise NotThisMethod("'git branch --contains' returned error")
+        branches = branches.split("\n")
+
+        # Remove the first line if we're running detached
+        if "(" in branches[0]:
+            branches.pop(0)
+
+        # Strip off the leading "* " from the list of branches.
+        branches = [branch[2:] for branch in branches]
+        if "master" in branches:
+            branch_name = "master"
+        elif not branches:
+            branch_name = None
+        else:
+            # Pick the first branch that is returned. Good or bad.
+            branch_name = branches[0]
+
+    pieces["branch"] = branch_name
+
     # parse describe_out. It will be like TAG-NUM-gHEX[-dirty] or HEX[-dirty]
     # TAG might have hyphens.
     git_describe = describe_out
@@ -270,7 +349,7 @@ def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
         # TAG-NUM-gHEX
         mo = re.search(r'^(.+)-(\d+)-g([0-9a-f]+)$', git_describe)
         if not mo:
-            # unparseable. Maybe git-describe is misbehaving?
+            # unparsable. Maybe git-describe is misbehaving?
             pieces["error"] = ("unable to parse git-describe output: '%s'"
                                % describe_out)
             return pieces
@@ -295,13 +374,11 @@ def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
     else:
         # HEX: no tags
         pieces["closest-tag"] = None
-        count_out, rc = run_command(GITS, ["rev-list", "HEAD", "--count"],
-                                    cwd=root)
-        pieces["distance"] = int(count_out)  # total number of commits
+        out, rc = runner(GITS, ["rev-list", "HEAD", "--left-right"], cwd=root)
+        pieces["distance"] = len(out.split())  # total number of commits
 
     # commit date: see ISO-8601 comment in git_versions_from_keywords()
-    date = run_command(GITS, ["show", "-s", "--format=%ci", "HEAD"],
-                       cwd=root)[0].strip()
+    date = runner(GITS, ["show", "-s", "--format=%ci", "HEAD"], cwd=root)[0].strip()
     # Use only the last line.  Previous lines may contain GPG signature
     # information.
     date = date.splitlines()[-1]
@@ -310,14 +387,14 @@ def git_pieces_from_vcs(tag_prefix, root, verbose, run_command=run_command):
     return pieces
 
 
-def plus_or_dot(pieces):
+def plus_or_dot(pieces: Dict[str, Any]) -> str:
     """Return a + if we don't already have one, else return a ."""
     if "+" in pieces.get("closest-tag", ""):
         return "."
     return "+"
 
 
-def render_pep440(pieces):
+def render_pep440(pieces: Dict[str, Any]) -> str:
     """Build up version string, with post-release "local version identifier".
 
     Our goal: TAG[+DISTANCE.gHEX[.dirty]] . Note that if you
@@ -342,23 +419,71 @@ def render_pep440(pieces):
     return rendered
 
 
-def render_pep440_pre(pieces):
-    """TAG[.post0.devDISTANCE] -- No -dirty.
+def render_pep440_branch(pieces: Dict[str, Any]) -> str:
+    """TAG[[.dev0]+DISTANCE.gHEX[.dirty]] .
+
+    The ".dev0" means not master branch. Note that .dev0 sorts backwards
+    (a feature branch will appear "older" than the master branch).
 
     Exceptions:
-    1: no tags. 0.post0.devDISTANCE
+    1: no tags. 0[.dev0]+untagged.DISTANCE.gHEX[.dirty]
     """
     if pieces["closest-tag"]:
         rendered = pieces["closest-tag"]
+        if pieces["distance"] or pieces["dirty"]:
+            if pieces["branch"] != "master":
+                rendered += ".dev0"
+            rendered += plus_or_dot(pieces)
+            rendered += "%d.g%s" % (pieces["distance"], pieces["short"])
+            if pieces["dirty"]:
+                rendered += ".dirty"
+    else:
+        # exception #1
+        rendered = "0"
+        if pieces["branch"] != "master":
+            rendered += ".dev0"
+        rendered += "+untagged.%d.g%s" % (pieces["distance"],
+                                          pieces["short"])
+        if pieces["dirty"]:
+            rendered += ".dirty"
+    return rendered
+
+
+def pep440_split_post(ver: str) -> Tuple[str, Optional[int]]:
+    """Split pep440 version string at the post-release segment.
+
+    Returns the release segments before the post-release and the
+    post-release version number (or -1 if no post-release segment is present).
+    """
+    vc = str.split(ver, ".post")
+    return vc[0], int(vc[1] or 0) if len(vc) == 2 else None
+
+
+def render_pep440_pre(pieces: Dict[str, Any]) -> str:
+    """TAG[.postN.devDISTANCE] -- No -dirty.
+
+    Exceptions:
+    1: no tags. 0.post0.devDISTANCE
+    """
+    if pieces["closest-tag"]:
         if pieces["distance"]:
-            rendered += ".post0.dev%d" % pieces["distance"]
+            # update the post release segment
+            tag_version, post_version = pep440_split_post(pieces["closest-tag"])
+            rendered = tag_version
+            if post_version is not None:
+                rendered += ".post%d.dev%d" % (post_version + 1, pieces["distance"])
+            else:
+                rendered += ".post0.dev%d" % (pieces["distance"])
+        else:
+            # no commits, use the tag as the version
+            rendered = pieces["closest-tag"]
     else:
         # exception #1
         rendered = "0.post0.dev%d" % pieces["distance"]
     return rendered
 
 
-def render_pep440_post(pieces):
+def render_pep440_post(pieces: Dict[str, Any]) -> str:
     """TAG[.postDISTANCE[.dev0]+gHEX] .
 
     The ".dev0" means dirty. Note that .dev0 sorts backwards
@@ -385,7 +510,36 @@ def render_pep440_post(pieces):
     return rendered
 
 
-def render_pep440_old(pieces):
+def render_pep440_post_branch(pieces: Dict[str, Any]) -> str:
+    """TAG[.postDISTANCE[.dev0]+gHEX[.dirty]] .
+
+    The ".dev0" means not master branch.
+
+    Exceptions:
+    1: no tags. 0.postDISTANCE[.dev0]+gHEX[.dirty]
+    """
+    if pieces["closest-tag"]:
+        rendered = pieces["closest-tag"]
+        if pieces["distance"] or pieces["dirty"]:
+            rendered += ".post%d" % pieces["distance"]
+            if pieces["branch"] != "master":
+                rendered += ".dev0"
+            rendered += plus_or_dot(pieces)
+            rendered += "g%s" % pieces["short"]
+            if pieces["dirty"]:
+                rendered += ".dirty"
+    else:
+        # exception #1
+        rendered = "0.post%d" % pieces["distance"]
+        if pieces["branch"] != "master":
+            rendered += ".dev0"
+        rendered += "+g%s" % pieces["short"]
+        if pieces["dirty"]:
+            rendered += ".dirty"
+    return rendered
+
+
+def render_pep440_old(pieces: Dict[str, Any]) -> str:
     """TAG[.postDISTANCE[.dev0]] .
 
     The ".dev0" means dirty.
@@ -407,7 +561,7 @@ def render_pep440_old(pieces):
     return rendered
 
 
-def render_git_describe(pieces):
+def render_git_describe(pieces: Dict[str, Any]) -> str:
     """TAG[-DISTANCE-gHEX][-dirty].
 
     Like 'git describe --tags --dirty --always'.
@@ -427,7 +581,7 @@ def render_git_describe(pieces):
     return rendered
 
 
-def render_git_describe_long(pieces):
+def render_git_describe_long(pieces: Dict[str, Any]) -> str:
     """TAG-DISTANCE-gHEX[-dirty].
 
     Like 'git describe --tags --dirty --always -long'.
@@ -447,7 +601,7 @@ def render_git_describe_long(pieces):
     return rendered
 
 
-def render(pieces, style):
+def render(pieces: Dict[str, Any], style: str) -> Dict[str, Any]:
     """Render the given version pieces into the requested style."""
     if pieces["error"]:
         return {"version": "unknown",
@@ -461,10 +615,14 @@ def render(pieces, style):
 
     if style == "pep440":
         rendered = render_pep440(pieces)
+    elif style == "pep440-branch":
+        rendered = render_pep440_branch(pieces)
     elif style == "pep440-pre":
         rendered = render_pep440_pre(pieces)
     elif style == "pep440-post":
         rendered = render_pep440_post(pieces)
+    elif style == "pep440-post-branch":
+        rendered = render_pep440_post_branch(pieces)
     elif style == "pep440-old":
         rendered = render_pep440_old(pieces)
     elif style == "git-describe":
@@ -479,7 +637,7 @@ def render(pieces, style):
             "date": pieces.get("date")}
 
 
-def get_versions():
+def get_versions() -> Dict[str, Any]:
     """Get version information or return default if unable to do so."""
     # I am in _version.py, which lives at ROOT/VERSIONFILE_SOURCE. If we have
     # __file__, we can work backwards from there to the root. Some
@@ -500,7 +658,7 @@ def get_versions():
         # versionfile_source is the relative path from the top of the source
         # tree (where the .git directory might live) to this file. Invert
         # this to find the root from __file__.
-        for i in cfg.versionfile_source.split('/'):
+        for _ in cfg.versionfile_source.split('/'):
             root = os.path.dirname(root)
     except NameError:
         return {"version": "0+unknown", "full-revisionid": None,

src/pystencils/assignment.py

+import numpy as np
+import sympy as sp
+from sympy.codegen.ast import Assignment, AugmentedAssignment
+from sympy.codegen.ast import AddAugmentedAssignment as SpAddAugAssignment
+from sympy.printing.latex import LatexPrinter
+
+__all__ = ['Assignment', 'AugmentedAssignment', 'AddAugmentedAssignment', 'assignment_from_stencil']
+
+
+def print_assignment_latex(printer, expr):
+    binop = f"{expr.binop}=" if isinstance(expr, AugmentedAssignment) else ''
+    """sympy cannot print Assignments as Latex. Thus, this function is added to the sympy Latex printer"""
+    printed_lhs = printer.doprint(expr.lhs)
+    printed_rhs = printer.doprint(expr.rhs)
+    return fr"{printed_lhs} \leftarrow_{{{binop}}} {printed_rhs}"
+
+
+def assignment_str(assignment):
+    op = f"{assignment.binop}=" if isinstance(assignment, AugmentedAssignment) else '←'
+    return fr"{assignment.lhs} {op} {assignment.rhs}"
+
+
+_old_new = sp.codegen.ast.Assignment.__new__
+
+
+# TODO Typing Part2 add default type, defult_float_type, default_int_type and use sane defaults
+def _Assignment__new__(cls, lhs, rhs, *args, **kwargs):
+    if isinstance(lhs, (list, tuple, sp.Matrix)) and isinstance(rhs, (list, tuple, sp.Matrix)):
+        assert len(lhs) == len(rhs), f'{lhs} and {rhs} must have same length when performing vector assignment!'
+        return tuple(_old_new(cls, a, b, *args, **kwargs) for a, b in zip(lhs, rhs))
+    return _old_new(cls, lhs, rhs, *args, **kwargs)
+
+
+Assignment.__str__ = assignment_str
+Assignment.__new__ = _Assignment__new__
+LatexPrinter._print_Assignment = print_assignment_latex
+
+AugmentedAssignment.__str__ = assignment_str
+LatexPrinter._print_AugmentedAssignment = print_assignment_latex
+
+sp.MutableDenseMatrix.__hash__ = lambda self: hash(tuple(self))
+
+#   Re-Export
+AddAugmentedAssignment = SpAddAugAssignment
+
+
+def assignment_from_stencil(stencil_array, input_field, output_field,
+                            normalization_factor=None, order='visual') -> Assignment:
+    """Creates an assignment
+
+    Args:
+        stencil_array: nested list of numpy array defining the stencil weights
+        input_field: field or field access, defining where the stencil should be applied to
+        output_field: field or field access where the result is written to
+        normalization_factor: optional normalization factor for the stencil
+        order: defines how the stencil_array is interpreted. Possible values are 'visual' and 'numpy'.
+               For details see examples
+
+    Returns:
+        Assignment that can be used to create a kernel
+
+    Examples:
+        >>> import pystencils as ps
+        >>> f, g = ps.fields("f, g: [2D]")
+        >>> stencil = [[0, 2, 0],
+        ...            [3, 4, 5],
+        ...            [0, 6, 0]]
+
+        By default 'visual ordering is used - i.e. the stencil is applied as the nested lists are written down
+        >>> expected_output = Assignment(g[0, 0], 3*f[-1, 0] + 6*f[0, -1] + 4*f[0, 0] + 2*f[0, 1] + 5*f[1, 0])
+        >>> assignment_from_stencil(stencil, f, g, order='visual') == expected_output
+        True
+
+        'numpy' ordering uses the first coordinate of the stencil array for x offset, second for y offset etc.
+        >>> expected_output = Assignment(g[0, 0], 2*f[-1, 0] + 3*f[0, -1] + 4*f[0, 0] + 5*f[0, 1] + 6*f[1, 0])
+        >>> assignment_from_stencil(stencil, f, g, order='numpy') == expected_output
+        True
+
+        You can also pass field accesses to apply the stencil at an already shifted position:
+        >>> expected_output = Assignment(g[2, 0], 3*f[0, 0] + 6*f[1, -1] + 4*f[1, 0] + 2*f[1, 1] + 5*f[2, 0])
+        >>> assignment_from_stencil(stencil, f[1, 0], g[2, 0]) == expected_output
+        True
+    """
+    from pystencils.field import Field
+
+    stencil_array = np.array(stencil_array)
+    if order == 'visual':
+        stencil_array = np.swapaxes(stencil_array, 0, 1)
+        stencil_array = np.flip(stencil_array, axis=1)
+    elif order == 'numpy':
+        pass
+    else:
+        raise ValueError("'order' has to be either 'visual' or 'numpy'")
+
+    if isinstance(input_field, Field):
+        input_field = input_field.center
+    if isinstance(output_field, Field):
+        output_field = output_field.center
+
+    rhs = 0
+    offset = tuple(s // 2 for s in stencil_array.shape)
+
+    for index, factor in np.ndenumerate(stencil_array):
+        shift = tuple(i - o for i, o in zip(index, offset))
+        rhs += factor * input_field.get_shifted(*shift)
+
+    if normalization_factor:
+        rhs *= normalization_factor
+
+    return Assignment(output_field, rhs)

src/pystencils/backend/kernelcreation/analysis.py

@@ -9,7 +9,8 @@ import sympy as sp
 from .context import KernelCreationContext
 
 from ...field import Field
-from ...sympyextensions import Assignment, AssignmentCollection
+from ...assignment import Assignment
+from ...simp import AssignmentCollection
 
 from ..exceptions import PsInternalCompilerError, KernelConstraintsError
 

src/pystencils/backend/kernelcreation/freeze.py

@@ -7,7 +7,8 @@ import sympy.core.relational
 import sympy.logic.boolalg
 from sympy.codegen.ast import AssignmentBase, AugmentedAssignment
 
-from ...sympyextensions.astnodes import Assignment, AssignmentCollection
+from ...assignment import Assignment
+from ...simp import AssignmentCollection
 from ...sympyextensions import (
     integer_functions,
     ConditionalFieldAccess,

src/pystencils/backend/kernelcreation/iteration_space.py

@@ -6,7 +6,7 @@ from functools import reduce
 from operator import mul
 
 from ...defaults import DEFAULTS
-from ...sympyextensions import AssignmentCollection
+from ...simp import AssignmentCollection
 from ...field import Field, FieldType
 
 from ..symbols import PsSymbol

src/pystencils/boundaries/boundaryconditions.py

 from typing import Any, List, Tuple, Sequence
 
-from pystencils.sympyextensions import Assignment
+from pystencils.assignment import Assignment
 from pystencils.boundaries.boundaryhandling import BoundaryOffsetInfo
 from pystencils.types import create_type
 

src/pystencils/boundaries/boundaryhandling.py

@@ -4,7 +4,7 @@ import numpy as np
 import sympy as sp
 
 from pystencils import create_kernel, CreateKernelConfig, Target
-from pystencils.sympyextensions import Assignment
+from pystencils.assignment import Assignment
 from pystencils.boundaries.createindexlist import (
     create_boundary_index_array, numpy_data_type_for_boundary_object)
 from pystencils.sympyextensions import TypedSymbol

src/pystencils/fd/derivation.py

@@ -6,7 +6,7 @@ import sympy as sp
 
 from pystencils.field import Field
 from pystencils.stencil import direction_string_to_offset
-from pystencils.sympyextensions.math import multidimensional_sum, prod
+from pystencils.sympyextensions import multidimensional_sum, prod
 from pystencils.utils import LinearEquationSystem, fully_contains
 
 

src/pystencils/fd/derivative.py

@@ -3,7 +3,7 @@ from collections import defaultdict, namedtuple
 import sympy as sp
 
 from pystencils.field import Field
-from pystencils.sympyextensions.math import normalize_product, prod
+from pystencils.sympyextensions import normalize_product, prod
 
 
 def _default_diff_sort_key(d):

src/pystencils/fd/finitedifferences.py

@@ -7,8 +7,8 @@ from pystencils.fd import Diff
 from pystencils.fd.derivative import diff_args
 from pystencils.fd.spatial import fd_stencils_standard
 from pystencils.field import Field
-from pystencils.sympyextensions import AssignmentCollection
-from pystencils.sympyextensions.math import fast_subs
+from pystencils.simp import AssignmentCollection
+from pystencils.sympyextensions import fast_subs
 
 FieldOrFieldAccess = Union[Field, Field.Access]
 

src/pystencils/field.py

@@ -15,8 +15,8 @@ from pystencils.alignedarray import aligned_empty
 from pystencils.spatial_coordinates import x_staggered_vector, x_vector
 from pystencils.stencil import direction_string_to_offset, inverse_direction, offset_to_direction_string
 from pystencils.types import PsType, PsStructType, create_type
-from pystencils.sympyextensions.typed_sympy import (FieldShapeSymbol, FieldStrideSymbol, TypedSymbol)
-from pystencils.sympyextensions.math import is_integer_sequence
+from pystencils.sympyextensions.typed_sympy import FieldShapeSymbol, FieldStrideSymbol, TypedSymbol
+from pystencils.sympyextensions import is_integer_sequence
 from pystencils.types import UserTypeSpec
 
 

src/pystencils/kernel_decorator.py

@@ -5,8 +5,8 @@ from typing import Callable, Union, List, Dict, Tuple
 
 import sympy as sp
 
-from .sympyextensions import Assignment
-from .sympyextensions.math import SymbolCreator
+from .assignment import Assignment
+from .sympyextensions import SymbolCreator
 from pystencils.config import CreateKernelConfig
 
 __all__ = ['kernel', 'kernel_config']

src/pystencils/kernelcreation.py

@@ -32,7 +32,8 @@ from .backend.transformations import (
     SelectFunctions,
 )
 
-from .sympyextensions import AssignmentCollection, Assignment
+from .simp import AssignmentCollection
+from .assignment import Assignment
 
 
 __all__ = ["create_kernel"]
@@ -152,3 +153,7 @@ def create_kernel_function(
     return KernelFunction(
         body, target_spec, function_name, params, req_headers, ctx.constraints, jit
     )
+
+
+def create_staggered_kernel(assignments, target: Target = Target.CPU, gpu_exclusive_conditions=False, **kwargs):
+    raise NotImplementedError("Staggered kernels are not yet implemented for pystencils 2.0")

src/pystencils/placeholder_function.py

@@ -2,7 +2,7 @@ from typing import List
 
 import sympy as sp
 
-from pystencils.sympyextensions import Assignment
+from .assignment import Assignment
 from pystencils.sympyextensions import is_constant
 from pystencils.sympyextensions.astnodes import generic_visit
 

src/pystencils/sympyextensions/rng.py → src/pystencils/rng.py

@@ -2,10 +2,9 @@ import copy
 import numpy as np
 import sympy as sp
 
-from pystencils.sympyextensions import TypedSymbol, CastFunc
+from .sympyextensions import TypedSymbol, CastFunc, fast_subs
 # from pystencils.sympyextensions.astnodes import LoopOverCoordinate # TODO nbackend: replace
 # from pystencils.backends.cbackend import CustomCodeNode # TODO nbackend: replace
-from pystencils.sympyextensions import fast_subs
 
 
 # class RNGBase(CustomCodeNode): TODO nbackend: replace

src/pystencils/simp/__init__.py

+from .assignment_collection import AssignmentCollection
+from .simplifications import (
+    add_subexpressions_for_constants,
+    add_subexpressions_for_divisions,
+    add_subexpressions_for_field_reads,
+    add_subexpressions_for_sums,
+    apply_on_all_subexpressions,
+    apply_to_all_assignments,
+    subexpression_substitution_in_existing_subexpressions,
+    subexpression_substitution_in_main_assignments,
+    sympy_cse,
+    sympy_cse_on_assignment_list,
+)
+from .subexpression_insertion import (
+    insert_aliases,
+    insert_zeros,
+    insert_constants,
+    insert_constant_additions,
+    insert_constant_multiples,
+    insert_squares,
+    insert_symbol_times_minus_one,
+)
+from .simplificationstrategy import SimplificationStrategy
+
+__all__ = [
+    "AssignmentCollection",
+    "SimplificationStrategy",
+    "sympy_cse",
+    "sympy_cse_on_assignment_list",
+    "apply_to_all_assignments",
+    "apply_on_all_subexpressions",
+    "subexpression_substitution_in_existing_subexpressions",
+    "subexpression_substitution_in_main_assignments",
+    "add_subexpressions_for_constants",
+    "add_subexpressions_for_divisions",
+    "add_subexpressions_for_sums",
+    "add_subexpressions_for_field_reads",
+    "insert_aliases",
+    "insert_zeros",
+    "insert_constants",
+    "insert_constant_additions",
+    "insert_constant_multiples",
+    "insert_squares",
+    "insert_symbol_times_minus_one",
+]

src/pystencils/simp/assignment_collection.py

+import itertools
+from copy import copy
+from typing import Any, Dict, Iterable, Iterator, List, Optional, Sequence, Set, Union
+
+import sympy as sp
+
+import pystencils
+from ..assignment import Assignment
+from .simplifications import (sort_assignments_topologically, transform_lhs_and_rhs, transform_rhs)
+from ..sympyextensions import count_operations, fast_subs
+
+
+class AssignmentCollection:
+    """
+    A collection of equations with subexpression definitions, also represented as assignments,
+    that are used in the main equations. AssignmentCollection can be passed to simplification methods.
+    These simplification methods can change the subexpressions, but the number and
+    left hand side of the main equations themselves is not altered.
+    Additionally a dictionary of simplification hints is stored, which are set by the functions that create
+    assignment collections to transport information to the simplification system.
+
+    Args:
+        main_assignments: List of assignments. Main assignments are characterised, that the right hand side of each
+                          assignment is a field access. Thus the generated equations write on arrays.
+        subexpressions: List of assignments defining subexpressions used in main equations
+        simplification_hints: Dict that is used to annotate the assignment collection with hints that are
+                              used by the simplification system. See documentation of the simplification rules for
+                              potentially required hints and their meaning.
+        subexpression_symbol_generator: Generator for new symbols that are used when new subexpressions are added
+                                        used to get new symbols that are unique for this AssignmentCollection
+
+    """
+
+    __match_args__ = ("main_assignments", "subexpressions")
+
+    # ------------------------------- Creation & Inplace Manipulation --------------------------------------------------
+
+    def __init__(self, main_assignments: Union[List[Assignment], Dict[sp.Expr, sp.Expr]],
+                 subexpressions: Union[List[Assignment], Dict[sp.Expr, sp.Expr]] = None,
+                 simplification_hints: Optional[Dict[str, Any]] = None,
+                 subexpression_symbol_generator: Iterator[sp.Symbol] = None) -> None:
+
+        if subexpressions is None:
+            subexpressions = {}
+
+        if isinstance(main_assignments, Dict):
+            main_assignments = [Assignment(k, v)
+                                for k, v in main_assignments.items()]
+        if isinstance(subexpressions, Dict):
+            subexpressions = [Assignment(k, v)
+                              for k, v in subexpressions.items()]
+
+        main_assignments = list(itertools.chain.from_iterable(
+            [(a if isinstance(a, Iterable) else [a]) for a in main_assignments]))
+        subexpressions = list(itertools.chain.from_iterable(
+            [(a if isinstance(a, Iterable) else [a]) for a in subexpressions]))
+
+        self.main_assignments = main_assignments
+        self.subexpressions = subexpressions
+
+        if simplification_hints is None:
+            simplification_hints = {}
+
+        self.simplification_hints = simplification_hints
+
+        ctrs = [int(n.name[3:])for n in self.rhs_symbols if "xi_" in n.name]
+        max_ctr = max(ctrs) + 1 if len(ctrs) > 0 else 0
+
+        if subexpression_symbol_generator is None:
+            self.subexpression_symbol_generator = SymbolGen(ctr=max_ctr)
+        else:
+            self.subexpression_symbol_generator = subexpression_symbol_generator
+
+    def add_simplification_hint(self, key: str, value: Any) -> None:
+        """Adds an entry to the simplification_hints dictionary and checks that is does not exist yet."""
+        assert key not in self.simplification_hints, "This hint already exists"
+        self.simplification_hints[key] = value
+
+    def add_subexpression(self, rhs: sp.Expr, lhs: Optional[sp.Symbol] = None, topological_sort=True) -> sp.Symbol:
+        """Adds a subexpression to current collection.
+
+        Args:
+            rhs: right hand side of new subexpression
+            lhs: optional left hand side of new subexpression. If None a new unique symbol is generated.
+            topological_sort: sort the subexpressions topologically after insertion, to make sure that
+                              definition of a symbol comes before its usage. If False, subexpression is appended.
+
+        Returns:
+            left hand side symbol (which could have been generated)
+        """
+        if lhs is None:
+            lhs = next(self.subexpression_symbol_generator)
+        eq = Assignment(lhs, rhs)
+        self.subexpressions.append(eq)
+        if topological_sort:
+            self.topological_sort(sort_subexpressions=True,
+                                  sort_main_assignments=False)
+        return lhs
+
+    def topological_sort(self, sort_subexpressions: bool = True, sort_main_assignments: bool = True) -> None:
+        """Sorts subexpressions and/or main_equations topologically to make sure symbol usage comes after definition."""
+        if sort_subexpressions:
+            self.subexpressions = sort_assignments_topologically(self.subexpressions)
+        if sort_main_assignments:
+            self.main_assignments = sort_assignments_topologically(self.main_assignments)
+
+    # ---------------------------------------------- Properties  -------------------------------------------------------
+
+    @property
+    def all_assignments(self) -> List[Assignment]:
+        """Subexpression and main equations as a single list."""
+        return self.subexpressions + self.main_assignments
+
+    @property
+    def rhs_symbols(self) -> Set[sp.Symbol]:
+        """All symbols used in the assignment collection, which occur on the rhs of any assignment."""
+        rhs_symbols = set()
+        for eq in self.all_assignments:
+            if isinstance(eq, Assignment):
+                rhs_symbols.update(eq.rhs.atoms(sp.Symbol))
+            # elif isinstance(eq, pystencils.astnodes.Node): # TODO remove or replace
+            #     rhs_symbols.update(eq.undefined_symbols)
+
+        return rhs_symbols
+
+    @property
+    def free_symbols(self) -> Set[sp.Symbol]:
+        """All symbols used in the assignment collection, which do not occur as left hand sides in any assignment."""
+        return self.rhs_symbols - self.bound_symbols
+
+    @property
+    def bound_symbols(self) -> Set[sp.Symbol]:
+        """All symbols which occur on the left hand side of a main assignment or a subexpression."""
+        bound_symbols_set = set(
+            [assignment.lhs for assignment in self.all_assignments if isinstance(assignment, Assignment)]
+        )
+
+        assert len(bound_symbols_set) == len(list(a for a in self.all_assignments if isinstance(a, Assignment))), \
+            "Not in SSA form - same symbol assigned multiple times"
+
+        # bound_symbols_set = bound_symbols_set.union(*[
+        #     assignment.symbols_defined for assignment in self.all_assignments
+        #     if isinstance(assignment, pystencils.astnodes.Node)
+        # ])  TODO: replace?
+
+        return bound_symbols_set
+
+    @property
+    def rhs_fields(self):
+        """All fields accessed in the assignment collection, which do not occur as left hand sides in any assignment."""
+        return {s.field for s in self.rhs_symbols if hasattr(s, 'field')}
+
+    @property
+    def free_fields(self):
+        """All fields accessed in the assignment collection, which do not occur as left hand sides in any assignment."""
+        return {s.field for s in self.free_symbols if hasattr(s, 'field')}
+
+    @property
+    def bound_fields(self):
+        """All field accessed on the left hand side of a main assignment or a subexpression."""
+        return {s.field for s in self.bound_symbols if hasattr(s, 'field')}
+
+    @property
+    def defined_symbols(self) -> Set[sp.Symbol]:
+        """All symbols which occur as left-hand-sides of one of the main equations"""
+        lhs_set = set([assignment.lhs for assignment in self.main_assignments if isinstance(assignment, Assignment)])
+        return lhs_set
+        # return (lhs_set.union(*[assignment.symbols_defined for assignment in self.main_assignments
+        #                         if isinstance(assignment, pystencils.astnodes.Node)])) TODO
+
+    @property
+    def operation_count(self):
+        """See :func:`count_operations` """
+        return count_operations(self.all_assignments, only_type=None)
+
+    def atoms(self, *args):
+        return set().union(*[a.atoms(*args) for a in self.all_assignments])
+
+    def dependent_symbols(self, symbols: Iterable[sp.Symbol]) -> Set[sp.Symbol]:
+        """Returns all symbols that depend on one of the passed symbols.
+
+        A symbol 'a' depends on a symbol 'b', if there is an assignment 'a <- some_expression(b)' i.e. when
+        'b' is required to compute 'a'.
+        """
+
+        queue = list(symbols)
+
+        def add_symbols_from_expr(expr):
+            dependent_symbols = expr.atoms(sp.Symbol)
+            for ds in dependent_symbols:
+                queue.append(ds)
+
+        handled_symbols = set()
+        assignment_dict = {e.lhs: e.rhs for e in self.all_assignments}
+
+        while len(queue) > 0:
+            e = queue.pop(0)
+            if e in handled_symbols:
+                continue
+            if e in assignment_dict:
+                add_symbols_from_expr(assignment_dict[e])
+            handled_symbols.add(e)
+
+        return handled_symbols
+
+    def lambdify(self, symbols: Sequence[sp.Symbol], fixed_symbols: Optional[Dict[sp.Symbol, Any]] = None, module=None):
+        """Returns a python function to evaluate this equation collection.
+
+        Args:
+            symbols: symbol(s) which are the parameter for the created function
+            fixed_symbols: dictionary with substitutions, that are applied before sympy's lambdify
+            module: same as sympy.lambdify parameter. Defines which module to use e.g. 'numpy'
+
+        Examples:
+              >>> a, b, c, d = sp.symbols("a b c d")
+              >>> ac = AssignmentCollection([Assignment(c, a + b), Assignment(d, a**2 + b)],
+              ...                           subexpressions=[Assignment(b, a + b / 2)])
+              >>> python_function = ac.lambdify([a], fixed_symbols={b: 2})
+              >>> python_function(4)
+              {c: 6, d: 18}
+        """
+        assignments = self.new_with_substitutions(fixed_symbols, substitute_on_lhs=False) if fixed_symbols else self
+        assignments = assignments.new_without_subexpressions().main_assignments
+        lambdas = {assignment.lhs: sp.lambdify(symbols, assignment.rhs, module) for assignment in assignments}
+
+        def f(*args, **kwargs):
+            return {s: func(*args, **kwargs) for s, func in lambdas.items()}
+
+        return f
+
+    # ---------------------------- Creating new modified collections ---------------------------------------------------
+
+    def copy(self,
+             main_assignments: Optional[List[Assignment]] = None,
+             subexpressions: Optional[List[Assignment]] = None) -> 'AssignmentCollection':
+        """Returns a copy with optionally replaced main_assignments and/or subexpressions."""
+
+        res = copy(self)
+        res.simplification_hints = self.simplification_hints.copy()
+        res.subexpression_symbol_generator = copy(self.subexpression_symbol_generator)
+
+        if main_assignments is not None:
+            res.main_assignments = main_assignments
+        else:
+            res.main_assignments = self.main_assignments.copy()
+
+        if subexpressions is not None:
+            res.subexpressions = subexpressions
+        else:
+            res.subexpressions = self.subexpressions.copy()
+
+        return res
+
+    def new_with_substitutions(self, substitutions: Dict, add_substitutions_as_subexpressions: bool = False,
+                               substitute_on_lhs: bool = True,
+                               sort_topologically: bool = True) -> 'AssignmentCollection':
+        """Returns new object, where terms are substituted according to the passed substitution dict.
+
+        Args:
+            substitutions: dict that is passed to sympy subs, substitutions are done main assignments and subexpressions
+            add_substitutions_as_subexpressions: if True, the substitutions are added as assignments to subexpressions
+            substitute_on_lhs: if False, the substitutions are done only on the right hand side of assignments
+            sort_topologically: if subexpressions are added as substitutions and this parameters is true,
+                                the subexpressions are sorted topologically after insertion
+        Returns:
+            New AssignmentCollection where substitutions have been applied, self is not altered.
+        """
+        transform = transform_lhs_and_rhs if substitute_on_lhs else transform_rhs
+        transformed_subexpressions = transform(self.subexpressions, fast_subs, substitutions)
+        transformed_assignments = transform(self.main_assignments, fast_subs, substitutions)
+
+        if add_substitutions_as_subexpressions:
+            transformed_subexpressions = [Assignment(b, a) for a, b in
+                                          substitutions.items()] + transformed_subexpressions
+            if sort_topologically:
+                transformed_subexpressions = sort_assignments_topologically(transformed_subexpressions)
+        return self.copy(transformed_assignments, transformed_subexpressions)
+
+    def new_merged(self, other: 'AssignmentCollection') -> 'AssignmentCollection':
+        """Returns a new collection which contains self and other. Subexpressions are renamed if they clash."""
+        own_definitions = set([e.lhs for e in self.main_assignments])
+        other_definitions = set([e.lhs for e in other.main_assignments])
+        assert len(own_definitions.intersection(other_definitions)) == 0, \
+            "Cannot merge collections, since both define the same symbols"
+
+        own_subexpression_symbols = {e.lhs: e.rhs for e in self.subexpressions}
+        substitution_dict = {}
+
+        processed_other_subexpression_equations = []
+        for other_subexpression_eq in other.subexpressions:
+            if other_subexpression_eq.lhs in own_subexpression_symbols:
+                new_rhs = fast_subs(other_subexpression_eq.rhs, substitution_dict)
+                if new_rhs == own_subexpression_symbols[other_subexpression_eq.lhs]:
+                    continue  # exact the same subexpression equation exists already
+                else:
+                    # different definition - a new name has to be introduced
+                    new_lhs = next(self.subexpression_symbol_generator)
+                    new_eq = Assignment(new_lhs, new_rhs)
+                    processed_other_subexpression_equations.append(new_eq)
+                    substitution_dict[other_subexpression_eq.lhs] = new_lhs
+            else:
+                processed_other_subexpression_equations.append(fast_subs(other_subexpression_eq, substitution_dict))
+
+        processed_other_main_assignments = [fast_subs(eq, substitution_dict) for eq in other.main_assignments]
+        return self.copy(self.main_assignments + processed_other_main_assignments,
+                         self.subexpressions + processed_other_subexpression_equations)
+
+    def new_filtered(self, symbols_to_extract: Iterable[sp.Symbol]) -> 'AssignmentCollection':
+        """Extracts equations that have symbols_to_extract as left hand side, together with necessary subexpressions.
+
+        Returns:
+            new AssignmentCollection, self is not altered
+        """
+        symbols_to_extract = set(symbols_to_extract)
+        dependent_symbols = self.dependent_symbols(symbols_to_extract)
+        new_assignments = []
+        for eq in self.all_assignments:
+            if eq.lhs in symbols_to_extract:
+                new_assignments.append(eq)
+
+        new_sub_expr = [eq for eq in self.all_assignments
+                        if eq.lhs in dependent_symbols and eq.lhs not in symbols_to_extract]
+        return self.copy(new_assignments, new_sub_expr)
+
+    def new_without_unused_subexpressions(self) -> 'AssignmentCollection':
+        """Returns new collection that only contains subexpressions required to compute the main assignments."""
+        all_lhs = [eq.lhs for eq in self.main_assignments]
+        return self.new_filtered(all_lhs)
+
+    def new_with_inserted_subexpression(self, symbol: sp.Symbol) -> 'AssignmentCollection':
+        """Eliminates the subexpression with the given symbol on its left hand side, by substituting it everywhere."""
+        new_subexpressions = []
+        subs_dict = None
+        for se in self.subexpressions:
+            if se.lhs == symbol:
+                subs_dict = {se.lhs: se.rhs}
+            else:
+                new_subexpressions.append(se)
+        if subs_dict is None:
+            return self
+
+        new_subexpressions = [Assignment(eq.lhs, fast_subs(eq.rhs, subs_dict)) for eq in new_subexpressions]
+        new_eqs = [Assignment(eq.lhs, fast_subs(eq.rhs, subs_dict)) for eq in self.main_assignments]
+        return self.copy(new_eqs, new_subexpressions)
+
+    def new_without_subexpressions(self, subexpressions_to_keep=None) -> 'AssignmentCollection':
+        """Returns a new collection where all subexpressions have been inserted."""
+        if subexpressions_to_keep is None:
+            subexpressions_to_keep = set()
+        if len(self.subexpressions) == 0:
+            return self.copy()
+
+        subexpressions_to_keep = set(subexpressions_to_keep)
+
+        kept_subexpressions = []
+        if self.subexpressions[0].lhs in subexpressions_to_keep:
+            substitution_dict = {}
+            kept_subexpressions.append(self.subexpressions[0])
+        else:
+            substitution_dict = {self.subexpressions[0].lhs: self.subexpressions[0].rhs}
+
+        subexpression = [e for e in self.subexpressions]
+        for i in range(1, len(subexpression)):
+            subexpression[i] = fast_subs(subexpression[i], substitution_dict)
+            if subexpression[i].lhs in subexpressions_to_keep:
+                kept_subexpressions.append(subexpression[i])
+            else:
+                substitution_dict[subexpression[i].lhs] = subexpression[i].rhs
+
+        new_assignment = [fast_subs(eq, substitution_dict) for eq in self.main_assignments]
+        return self.copy(new_assignment, kept_subexpressions)
+
+    # ----------------------------------------- Display and Printing   -------------------------------------------------
+
+    def _repr_html_(self):
+        """Interface to Jupyter notebook, to display as a nicely formatted HTML table"""
+
+        def make_html_equation_table(equations):
+            no_border = 'style="border:none"'
+            html_table = '<table style="border:none; width: 100%; ">'
+            line = '<tr {nb}> <td {nb}>$${eq}$$</td>  </tr> '
+            for eq in equations:
+                format_dict = {'eq': sp.latex(eq),
+                               'nb': no_border, }
+                html_table += line.format(**format_dict)
+            html_table += "</table>"
+            return html_table
+
+        result = ""
+        if len(self.subexpressions) > 0:
+            result += "<div>Subexpressions:</div>"
+            result += make_html_equation_table(self.subexpressions)
+        result += "<div>Main Assignments:</div>"
+        result += make_html_equation_table(self.main_assignments)
+        return result
+
+    def __repr__(self):
+        return f"AssignmentCollection: {str(tuple(self.defined_symbols))[1:-1]} <- f{tuple(self.free_symbols)}"
+
+    def __str__(self):
+        result = "Subexpressions:\n"
+        for eq in self.subexpressions:
+            result += f"\t{eq}\n"
+        result += "Main Assignments:\n"
+        for eq in self.main_assignments:
+            result += f"\t{eq}\n"
+        return result
+
+    def __iter__(self):
+        return self.all_assignments.__iter__()
+
+    @property
+    def main_assignments_dict(self):
+        return {a.lhs: a.rhs for a in self.main_assignments}
+
+    @property
+    def subexpressions_dict(self):
+        return {a.lhs: a.rhs for a in self.subexpressions}
+
+    def set_main_assignments_from_dict(self, main_assignments_dict):
+        self.main_assignments = [Assignment(k, v)
+                                 for k, v in main_assignments_dict.items()]
+
+    def set_sub_expressions_from_dict(self, sub_expressions_dict):
+        self.subexpressions = [Assignment(k, v)
+                               for k, v in sub_expressions_dict.items()]
+
+    def find(self, *args, **kwargs):
+        return set.union(
+            *[a.find(*args, **kwargs) for a in self.all_assignments]
+        )
+
+    def match(self, *args, **kwargs):
+        rtn = {}
+        for a in self.all_assignments:
+            partial_result = a.match(*args, **kwargs)
+            if partial_result:
+                rtn.update(partial_result)
+        return rtn
+
+    def subs(self, *args, **kwargs):
+        return AssignmentCollection(
+            main_assignments=[a.subs(*args, **kwargs) for a in self.main_assignments],
+            subexpressions=[a.subs(*args, **kwargs) for a in self.subexpressions]
+        )
+
+    def replace(self, *args, **kwargs):
+        return AssignmentCollection(
+            main_assignments=[a.replace(*args, **kwargs) for a in self.main_assignments],
+            subexpressions=[a.replace(*args, **kwargs) for a in self.subexpressions]
+        )
+
+    def __eq__(self, other):
+        return set(self.all_assignments) == set(other.all_assignments)
+
+    def __bool__(self):
+        return bool(self.all_assignments)
+
+
+class SymbolGen:
+    """Default symbol generator producing number symbols ζ_0, ζ_1, ..."""
+
+    def __init__(self, symbol="xi", dtype=None, ctr=0):
+        self._ctr = ctr
+        self._symbol = symbol
+        self._dtype = dtype
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        name = f"{self._symbol}_{self._ctr}"
+        self._ctr += 1
+        if self._dtype is not None:
+            return pystencils.TypedSymbol(name, self._dtype)
+        return sp.Symbol(name)