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[Octave-bug-tracker] [bug #36562] Sparse matrix operations with NaN do n
From: |
Rik |
Subject: |
[Octave-bug-tracker] [bug #36562] Sparse matrix operations with NaN do not follow IEEE standard |
Date: |
Thu, 31 May 2012 20:43:27 +0000 |
User-agent: |
Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:12.0) Gecko/20100101 Firefox/12.0 |
Update of bug #36562 (project octave):
Status: None => Confirmed
Summary: NaN/Inf behaviour unexpected in sparse rdivide =>
Sparse matrix operations with NaN do not follow IEEE standard
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Follow-up Comment #1:
Confirmed on a recent (5/31/12) development tip.
The issue is more general than just divide so I have changed the bug Summary.
At present, I can verify that multiply and divide are affected while addition
and subtraction behaves correctly.
The issue appears to be a side effect of the way that sparse matrices improve
calculation performance. In general, math operations like multiply and divide
only need to be performed on the non-zero elements of a sparse matrix.
However, a NaN is different and should affect all elements of the matrix.
Below is some simple code to illustrate the problem.
Mfull = [1 0; 0 3];
Msparse = sparse (Mfull);
NaN .* Mfull
ans =
NaN NaN
NaN NaN
NaN .* Msparse
ans =
Compressed Column Sparse (rows = 2, cols = 2, nnz = 2 [50%])
(1, 1) -> NaN
(2, 2) -> NaN
NaN ./ Mfull
ans =
NaN NaN
NaN NaN
NaN ./ Msparse
ans =
NaN -Inf
-Inf NaN
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