TensorProduct of sparse matrices failing

[Edward Dahl]

I'd like to form some tensor products of sparse matrices, but this does not seem to work:

from sympy import diag
from sympy.physics.quantum import TensorProduct
from sympy.matrices import SparseMatrix

spm = SparseMatrix(diag(1,0))

tp = TensorProduct(spm,spm)

Here's the failure:

Traceback (most recent call last):

  File "/Users/ddahl/anaconda3/envs/qiskit/lib/python3.8/site-packages/IPython/core/interactiveshell.py", line 3331, in run_code

    exec(code_obj, self.user_global_ns, self.user_ns)

  File "<ipython-input-9-88417d1a4157>", line 1, in <module>

    tp = TensorProduct(spm,spm)

  File "/Users/ddahl/anaconda3/envs/qiskit/lib/python3.8/site-packages/sympy/physics/quantum/tensorproduct.py", line 123, in __new__

    c_part, new_args = cls.flatten(sympify(args))

  File "/Users/ddahl/anaconda3/envs/qiskit/lib/python3.8/site-packages/sympy/physics/quantum/tensorproduct.py", line 139, in flatten

    cp, ncp = arg.args_cnc()

  File "/Users/ddahl/anaconda3/envs/qiskit/lib/python3.8/site-packages/sympy/matrices/matrices.py", line 2339, in __getattr__

    raise AttributeError(

AttributeError: ImmutableSparseMatrix has no attribute args_cnc.

When I look in sympy/physics/quantum/tensorproduct.py it looks to me like there is an attempted test to determine

whether the first argument to the TensorProduct(...) function is a sparse SciPy matrix:

def __new__(cls, *args):
    if isinstance(args[0], (Matrix, numpy_ndarray, scipy_sparse_matrix)):
        return matrix_tensor_product(*args)
    c_part, new_args = cls.flatten(sympify(args))
    c_part = Mul(*c_part)
    if len(new_args) == 0:
        return c_part
    elif len(new_args) == 1:
        return c_part * new_args[0]
    else:
        tp = Expr.__new__(cls, *new_args)
        return c_part * tp

But according to my debugger, the isinstance(...) call in the above code block returns false.

Looks to me like that sparse matrix should be of type scipy_sparse_matrix.

My environment is a freshly built Anaconda from two weeks ago and I'm running on macOS.

What am I missing?

Thanks,

-Denny

[Aaron Meurer]

This looks like a bug. Can you open an issue for it? I think it should
be using isinstance(MatrixBase) instead of isinstance(Matrix).

Aaron Meurer

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[Edward Dahl]

Sure thing, Aaron.  I opened an issue - it's #19227.

-Denny

On Tuesday, April 28, 2020 at 12:18:19 PM UTC-6, Aaron Meurer wrote:

This looks like a bug. Can you open an issue for it? I think it should
be using isinstance(MatrixBase) instead of isinstance(Matrix).

Aaron Meurer

> To unsubscribe from this group and stop receiving emails from it, send an email to sy...@googlegroups.com.