Import of fastcalc raises ImportError

[haroldmeerwaldt]

Describe the bug
When I import the pygsti.modelpacks.smq2Q_XYICNOT module, I get an ImportError.

To Reproduce
Steps to reproduce the behavior:

1. make virtual environment with venv
2. pip install pygsti
3. in Python: from pygsti.modelpacks import smq2Q_XYICNOT
4. See error:

C:\YYY\env\Lib\site-packages\pygsti\baseobjs\opcalc\__init__.py:31: UserWarning: 
An optimized Cython-based implementation of `pygsti.baseobjs.opcalc` is available as
an extension, but couldn't be imported. This might happen if the
extension has not been built. `pip install cython`, then reinstall
pyGSTi to build Cython extensions. Alternatively, setting the
environment variable `PYGSTI_NO_CYTHON_WARNING` will suppress this
message.

  _warnings.warn(warn_msg)
Traceback (most recent call last):
  File "C:\XXX\scratch_30.py", line 1, in <module>
    from pygsti.modelpacks import smq2Q_XYICNOT
  File "C:\YYY\env\Lib\site-packages\pygsti\__init__.py", line 12, in <module>
    from . import algorithms as alg
  File "C:\YYY\env\Lib\site-packages\pygsti\algorithms\__init__.py", line 17, in <module>
    from .contract import *
  File "C:\YYY\env\Lib\site-packages\pygsti\algorithms\contract.py", line 18, in <module>
    from pygsti import optimize as _opt
  File "C:\YYY\env\Lib\site-packages\pygsti\optimize\__init__.py", line 14, in <module>
    from .customlm import *
  File "C:\YYY\env\Lib\site-packages\pygsti\optimize\customlm.py", line 22, in <module>
    from pygsti.optimize.simplerlm import Optimizer, OptimizerResult
  File "C:\YYY\env\Lib\site-packages\pygsti\optimize\simplerlm.py", line 25, in <module>
    from pygsti.objectivefns.objectivefns import Chi2Function, TimeIndependentMDCObjectiveFunction
  File "C:\YYY\env\Lib\site-packages\pygsti\objectivefns\__init__.py", line 13, in <module>
    from .objectivefns import ObjectiveFunctionBuilder, \
  File "C:\YYY\env\Lib\site-packages\pygsti\objectivefns\objectivefns.py", line 28, in <module>
    from pygsti.models.model import OpModel as _OpModel
  File "C:\YYY\env\Lib\site-packages\pygsti\models\__init__.py", line 14, in <module>
    from .cloudnoisemodel import CloudNoiseModel
  File "C:\YYY\env\Lib\site-packages\pygsti\models\cloudnoisemodel.py", line 21, in <module>
    from pygsti.models.implicitmodel import ImplicitOpModel as _ImplicitOpModel, _init_spam_layers
  File "C:\YYY\env\Lib\site-packages\pygsti\models\implicitmodel.py", line 18, in <module>
    from pygsti.models import model as _mdl
  File "C:\YYY\env\Lib\site-packages\pygsti\models\model.py", line 23, in <module>
    from pygsti.models.layerrules import LayerRules as _LayerRules
  File "C:\YYY\env\Lib\site-packages\pygsti\models\layerrules.py", line 14, in <module>
    from pygsti.modelmembers import operations as _op
  File "C:\YYY\env\Lib\site-packages\pygsti\modelmembers\operations\__init__.py", line 17, in <module>
    from .composedop import ComposedOp
  File "C:\YYY\env\Lib\site-packages\pygsti\modelmembers\operations\composedop.py", line 19, in <module>
    from pygsti.modelmembers.operations.experrorgenop import ExpErrorgenOp as _ExpErrorgenOp
  File "C:\YYY\env\Lib\site-packages\pygsti\modelmembers\operations\experrorgenop.py", line 22, in <module>
    from pygsti.modelmembers.operations.lindbladerrorgen import LindbladParameterization as _LindbladParameterization
  File "C:\YYY\env\Lib\site-packages\pygsti\modelmembers\operations\lindbladerrorgen.py", line 27, in <module>
    from pygsti.modelmembers.operations.lindbladcoefficients import LindbladCoefficientBlock as _LindbladCoefficientBlock
  File "C:\YYY\env\Lib\site-packages\pygsti\modelmembers\operations\lindbladcoefficients.py", line 11, in <module>
    from pygsti.tools import fastcalc as _fc
ImportError: cannot import name 'fastcalc' from 'pygsti.tools' (C:\YYY\env\Lib\site-packages\pygsti\tools\__init__.py)

Expected behavior
I expected to be able to import the module without error.

Environment (please complete the following information):

• pyGSTi version 0.9.13
• python version 3.12.8
• OS: Windows 11, 10.0.22631

Additional context

• also occurs with cython installed before installing pygsti

[sserita]

Hi @haroldmeerwaldt, thanks for the report! This is probably a quick fix, looks like we are not guarding fastcalc properly here.

But in the meantime, can you try running python setup.py build_ext --inplace in your pyGSTi directory to force the Cython extensions to recompile and see if that fixes things?

[haroldmeerwaldt]

Hi @sserita, thank you for looking at this.

I did an editable [complete] install of pyGSTi in the virtual environment after cloning the repository (pyGSTi 0.9.13.post3) and could import fastcalc successfully. There is a fastcalc.cp312-win_amd64.pyd file in pygsti.tools.

I am assuming you meant running python setup.py build_ext --inplace for building from source; in the end I didn't need to.

If I then pip install pygsti==0.9.13 for the pypi package again, I cannot import fastcalc. There is no fastcalc.cp312-win_amd64.pyd file in pygsti.tools.