blas IndexError: list index out of range error

[twiecki]

Description

~ $ python -c "import pytensor"
WARNING (pytensor.configdefaults): g++ not detected!  PyTensor will be unable to compile C-implementations and will default to Python. Performance may be severely degraded. To remove this warning, set PyTensor flags cxx to an empty string.
Traceback (most recent call last):
  File "/app/.heroku/python/lib/python3.11/site-packages/pytensor/configparser.py", line 202, in fetch_val_for_key
    return self._pytensor_cfg.get(section, option)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/app/.heroku/python/lib/python3.11/configparser.py", line 797, in get
    d = self._unify_values(section, vars)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/app/.heroku/python/lib/python3.11/configparser.py", line 1168, in _unify_values
    raise NoSectionError(section) from None
configparser.NoSectionError: No section: 'blas'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/app/.heroku/python/lib/python3.11/site-packages/pytensor/configparser.py", line 318, in __get__
    val_str = cls.fetch_val_for_key(self.name, delete_key=delete_key)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/app/.heroku/python/lib/python3.11/site-packages/pytensor/configparser.py", line 206, in fetch_val_for_key
    raise KeyError(key)
KeyError: 'blas__ldflags'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/app/.heroku/python/lib/python3.11/site-packages/pytensor/__init__.py", line 119, in <module>
    from pytensor import scalar, tensor
  File "/app/.heroku/python/lib/python3.11/site-packages/pytensor/tensor/__init__.py", line 107, in <module>
    from pytensor.tensor import (  # noqa
  File "/app/.heroku/python/lib/python3.11/site-packages/pytensor/tensor/blas.py", line 101, in <module>
    from pytensor.tensor.blas_headers import blas_header_text, blas_header_version
  File "/app/.heroku/python/lib/python3.11/site-packages/pytensor/tensor/blas_headers.py", line 1015, in <module>
    if not config.blas__ldflags:
           ^^^^^^^^^^^^^^^^^^^^
  File "/app/.heroku/python/lib/python3.11/site-packages/pytensor/configparser.py", line 322, in __get__
    val_str = self.default()
              ^^^^^^^^^^^^^^
  File "/app/.heroku/python/lib/python3.11/site-packages/pytensor/link/c/cmodule.py", line 2782, in default_blas_ldflags
    cxx_library_dirs = get_cxx_library_dirs()
                       ^^^^^^^^^^^^^^^^^^^^^^
  File "/app/.heroku/python/lib/python3.11/site-packages/pytensor/link/c/cmodule.py", line 2734, in get_cxx_library_dirs
    maybe_lib_dirs = [
                     ^
IndexError: list index out of range

Could be related to #444 ? CC @lucianopaz

[twiecki]

It works when I install clang++ and openblas.

[ricardoV94]

Is that a truncated stack track? Where is the indexing operation actually happening?

[twiecki]

It's the full traceback I got.

[lucianopaz]

This happens because the default blas config function fails to find a cxx compiler to query for the search paths. We should add a try or if block to see if the compiler exists and if it doesn't return an empty string as the blas ld flags