dlr-sc / f2x

A versatile, template-based FORTRAN wrapper written in Python.

F2x

A versatile, template-based Fortran wrapper written in Python.

F2x is a Python tool that allows you to take your Fortran code and make it accessible from other languages (mainly Python). Compared to the popular tool f2py it comes with two important differences:

• A full Fortran parser based on the work by the OpenFortranParser
• A very flexible code generation backend that uses Jinja2 templates

Quickstart

To install the latest version of F2x, you can use the following commands:

1. git clone https://github.com/DLR-SC/F2x.git
2. cd F2x
3. python setup.py install --user (Note the --user flag to allow installation without admin rights.)
4. F2x --help (Confirms installation of F2x.)

Please refer to the documentation to find more infomation about getting started.

Requirements and acknowledgements

F2x reuses a lot of stuff from other Open Source projects. Namely the following parts were really helpful:

• It is developed in Python 3 and does currently not support Python 2 out of the box.
• The PLY project is used as parser generator. PlyPlus does the heavy lifiting of converting ANTLR-like grammars to PLY.
• The Fortran grammar that comes bundled with F2x originates from the OpenFortranProject.
• Templates are based on Jinja2.

Legal stuff

Copyright 2018 German Aerospace Center (DLR)

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

f2x's Issues

Add a 'serialize' method to be usered by jsonify

The wrapped derived types should be able to serialze to JSON.

Support for fixed-form Syntax

Maybe this can be achieved by a different preprocessor, otherwise another grammar needs to be created.

Prepare for publication

• Review documentation
  • Adapt Readme for getting started
  • Review other documenation, at least add a note where it is superceeded
• Add copyright to all files
• Add citation hint
• Tag version "1.0"

No support for Fortran Interfaces

Currently, there is no support for the interface construct.
Also the parser accepts those constructs, they are not handled by the templates and AST transformers.

Calculate correct size for MALLOC

Depending on the environment (32/64 bit), the correct suffix for the fortran wrapper code needs to be determined.

Support for String-Arrays in derived types

Arrays of (fixed-length) character variables should be supported by the wrapper.

[template-bindc] Subroutines are not wrapped

Even when they are listed in the [export] section, subroutines are not yet exported to the BIND-C Fortran wrapper.

The 'F2x==0.1.dev0' distribution was not found

After installing F2x on a SLED12 using our module system, I obtain the following error:

F2x --help
Traceback (most recent call last):
File "/tools/modulesystem/tools/F2x/F2x-git/install/sled12.x86_64.gcc-4.8.5.release/bin/F2x", line 5, in
from pkg_resources import load_entry_point
File "/usr/lib/python2.7/site-packages/pkg_resources/init.py", line 2912, in
@_call_aside
File "/usr/lib/python2.7/site-packages/pkg_resources/init.py", line 2898, in _call_aside
f(_args, *_kwargs)
File "/usr/lib/python2.7/site-packages/pkg_resources/init.py", line 2925, in _initialize_master_working_set
working_set = WorkingSet._build_master()
File "/usr/lib/python2.7/site-packages/pkg_resources/init.py", line 642, in _build_master
ws.require(requires)
File "/usr/lib/python2.7/site-packages/pkg_resources/init.py", line 943, in require
needed = self.resolve(parse_requirements(requirements))
File "/usr/lib/python2.7/site-packages/pkg_resources/init.py", line 830, in resolve
raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'F2x==0.1.dev0' distribution was not found and is required by the application

There might just be some missing paths or so...any idea?

Here the output of the install script: f2x_install_sled12.zip

Support Intel Fortran

Fortran code should be compiled by Intel Fortran Compiler if present and wanted.

Syntax errors for valid Fortran

The Fortran grammar specification has several issues:

1. Kind-specifiers for constants are not supported, e.g. 1.0_8 or 1.0_myKindParameter
2. kind is not only a keyword inside a declaration, but also an intrinsic function, e.g. i = kind(1.)
3. Fortran explicitly allows reusing keywords of the language. Keywords are not reserved, you can for example name a variable value or kind. The compiler only fails if the usage is ambigious.

Here is a valid Fortran file:

module test
  implicit none
  public

  integer, parameter :: rk = kind(1.0)
  real(kind=rk), parameter :: eps = epsilon(1._rk)
  integer, parameter :: value = 10

end module test

And the respective errors I obtain:

> F2x -t @_bindc.f90.t -t @_ctypes.py.t test.f90
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home_local/zoel_ml/F2x/src/F2x/main.py", line 165, in main
    src.parse()
  File "/home_local/zoel_ml/F2x/src/F2x/source.py", line 180, in parse
    self.tree = grammar.parse(self.source)
  File "/home_local/zoel_ml/F2x/src/plyplus/plyplus.py", line 575, in parse
    return self._grammar.parse(text)
  File "/home_local/zoel_ml/F2x/src/plyplus/plyplus.py", line 716, in parse
    raise ParseError('\n'.join(self.errors))
plyplus.plyplus.ParseError: Syntax error in input at 'kind' (type T_KIND) line 5 col 30
Syntax error in input at '_' (type T_UNDERSCORE) line 6 col 47
Syntax error in input at 'value' (type T_VALUE) line 7 col 25
Could not create parse tree!

Error when running `mylib` example since d40f96d

When running the example according to https://f2x.readthedocs.io/en/latest/content/introduction/getting_started.html the following error occurs in master and the previous commit d40f96d:

$~/code/F2x/draft$ F2x -W lib -m mylib.* mylib/test.f90
INFO  F2x Version 0.2
Traceback (most recent call last):
  File "/usr/local/bin/F2x", line 11, in <module>
    load_entry_point('F2x', 'console_scripts', 'F2x')()
  File "/home/calbert/code/F2x/src/F2x/runtime/main.py", line 157, in main
    for template_package in args.register_template:
TypeError: 'NoneType' object is not iterable

With earlier versions this is working fine.

Automatically ignore execution part

The execution part contains irrelevant information for wrapper generation but makes the grammar more complex. Hence, it is a good idea to ignore it.

Automatic ignore does not handle continuations

Line continuations (&) are not handled correctly in some cases/states.

Improve Parser

• Make Preprocessor ignore execution part (#14)
• Reduce Grammar