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Bug 1005

Summary:

Error with sparse vector and transpose of matrix

Product:

Eigen

Reporter:

Benjamin Chretien <chretien>

Component:

Sparse

Assignee:

Nobody <eigen.nobody>

Status:

RESOLVED FIXED

Severity:

Wrong Result

CC:

chtz, gael.guennebaud

Priority:

Normal

Version:

3.3 (current stable)

Hardware:

All

OS:

All

Whiteboard:

Bug Depends on:

Bug Blocks:

558

Attachments:

Description	Flags
Repro code	none

Description Benjamin Chretien 2015-04-27 04:15:26 UTC

Created attachment 566 [details]
Repro code

While trying to see whether #980 (http://eigen.tuxfamily.org/bz/show_bug.cgi?id=980) was solved on the default branch with one of our tests, I noticed an error in the actual result. If we do:

  v += m1.transpose ();

where v is a SparseVector<double> and m a SparseMatrix<double> with the adequate size, some inner loop in Eigen's code appears to be done with the wrong size (1 instead of the vector size), resulting in a wrong result.

Repro code: https://gist.github.com/bchretien/29827af68edae49cd6d7 (attached)

Output:

(1,2)
(1,2)
(1,2)
(2,2)
(3,4)

Expected output:

(1,2)
(1,2)
(1,2)
(2,4)
(3,6)

Comment 1 Christoph Hertzberg 2015-04-27 15:08:43 UTC

Here is a workaround until this gets fixed:
  v += sparseVector_t(m1.transpose ());

Comment 2 Gael Guennebaud 2015-06-08 07:34:31 UTC

Since the storage order of v and m1.transpose do not match, this should not even compile (this is the case with eigen 3.2). I also see that "sparse colmajor" + "sparse rowmajor" does compile in the devel branch, meaning that a static assert has been improperly deactivated. Let me investigate...

Comment 3 Gael Guennebaud 2015-06-08 08:28:39 UTC

Fixed. Let me also emphasize that the "workaround" proposed by Christoph is actually not a workaround, but a requirement.

https://bitbucket.org/eigen/eigen/commits/e99ca53c931b/
Changeset:   e99ca53c931b
User:        ggael
Date:        2015-06-08 08:14:08+00:00
Summary:     Bug 1005: fix regression regarding sparse coeff-wise binary operator that did not trigger a static assertion for mismatched storage

Comment 4 Nobody 2019-12-04 14:34:16 UTC

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