Memory Acess Error with fm.Blocks and fm.Sparse

[JanKirchhofTU]

Say I have two sparse matrices and I want to construct a block matrix from those:

import scipy.sparse
import fastmat as fm

a = fm.Sparse(
scipy.sparse.csr_matrix((3, 5))
)
b = fm.Sparse(
scipy.sparse.csr_matrix((3, 5))
)

# This works as expected
c = fm.Blocks([[a,b], [a,b]])
# This works as expected
d = fm.Blocks([[a,b]])
# This crashes with a Memory Access Error
e = fm.Blocks([a,b])

I am running

• fastmat0.2a4
• scipy1.3.3
• python 3.8.1

on a linux system.

[ChristophWWagner]

This one is a tough one as it is a good example for an "ungraceful fail" and should produce a more meaningful error message.

Blocks expects a double list. However, since you can index into fastmat matrices this is what probably happens at the second level. Duck typing ftw! The problem, unfortunately, lies in deciding what not do disallow in order to get this thing cleaner without impacting duck typing magic too much.

My suggestion would be to specifically disallow fastmat.Matrix as second-level container.

Other suggestions?

[SebastianSemper]

Would go down the same route. The supplied list should always contain another list, but then we should also check, if at the third level we finally have a matrix.

On Mon, 13 Jan 2020 at 15:02, Christoph Wagner notifications@github.com wrote:

This one is a tough one as it is a good example for an "ungraceful fail" and should produce a more meaningful error message.

Blocks expects a double list. However, since you can index into fastmat matrices this is what probably happens at the second level. Duck typing ftw! The problem, unfortunately, lies in deciding what not do disallow in order to get this thing cleaner without impacting duck typing magic too much.

My suggestion would be to specifically disallow fastmat.Matrix as second-level container.

Other suggestions?

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[ChristophWWagner]

In e24862c such an error message, warning about broken second iteration levels in the structure passed to Blocks.__init__(), was added. Hope that's enough to mitigate crashes from this failure vector in the future. Closing. Feel free to reopen if problems still persist.