Error in scipy sparse: multiplication with coo_matrix copy changes the data and the format of the multiplied

After multiplying a coo_matrix from scipy.sparse with its copy, the copy's
format changes to column-major and hence its data change while the original
data remains the same.

Example:
import numpy, scipy
from scipy.sparse import coo_matrix, csc_matrix

a = numpy.random.randn(4,7)
print ('a:', a)
b = coo_matrix(a)
c = b.copy()
print ('c before (coo_matrix):', c)
print ('c data before (coo_matrix):', c.data)
b.multiply(c)
print ('c after (coo_matrix):', c)
print ('c data after (coo_matrix):', c.data)

a: [[ 0.80168251 -1.39944231  0.25345622  1.42371329 -0.12530735
 0.50449369
  1.07289013]
[ 0.45875588 -0.15916679 -0.42632756  0.56484416 -1.46640872  1.42488646
  0.03532664]
[ 0.72752298  1.34140445 -0.37043453  0.78127267  0.01084105 -2.08957963
 -0.10899932]
[-0.02555597 -0.87197938 -0.76835675  0.82776032 -2.06292275 -1.2911363
 -0.72253431]]
c before (coo_matrix):   (0, 0) 0.801682509603
 (0, 1)        -1.39944230956
 (0, 2)        0.253456223565
 (0, 3)        1.4237132942
 (0, 4)        -0.125307347426
 (0, 5)        0.504493692248
 (0, 6)        1.07289013113
 (1, 0)        0.458755875333
 (1, 1)        -0.159166794146
 (1, 2)        -0.426327564398
 (1, 3)        0.564844163879
 (1, 4)        -1.46640871661
 (1, 5)        1.42488646441
 (1, 6)        0.0353266410166
 (2, 0)        0.727522979291
 (2, 1)        1.34140444948
 (2, 2)        -0.370434529077
 (2, 3)        0.781272667369
 (2, 4)        0.0108410499861
 (2, 5)        -2.08957962801
 (2, 6)        -0.108999316299
 (3, 0)        -0.0255559745129
 (3, 1)        -0.871979375733
 (3, 2)        -0.768356754242
 (3, 3)        0.827760318972
 (3, 4)        -2.0629227477
 (3, 5)        -1.29113629796
 (3, 6)        -0.722534309773
c data before (coo_matrix): [ 0.80168251 -1.39944231  0.25345622
 1.42371329 -0.12530735  0.50449369
 1.07289013  0.45875588 -0.15916679 -0.42632756  0.56484416 -1.46640872
 1.42488646  0.03532664  0.72752298  1.34140445 -0.37043453  0.78127267
 0.01084105 -2.08957963 -0.10899932 -0.02555597 -0.87197938 -0.76835675
 0.82776032 -2.06292275 -1.2911363  -0.72253431]
c after (coo_matrix):   (0, 0)  0.801682509603
 (1, 0)        0.458755875333
 (2, 0)        0.727522979291
 (3, 0)        -0.0255559745129
 (0, 1)        -1.39944230956
 (1, 1)        -0.159166794146
 (2, 1)        1.34140444948
 (3, 1)        -0.871979375733
 (0, 2)        0.253456223565
 (1, 2)        -0.426327564398
 (2, 2)        -0.370434529077
 (3, 2)        -0.768356754242
 (0, 3)        1.4237132942
 (1, 3)        0.564844163879
 (2, 3)        0.781272667369
 (3, 3)        0.827760318972
 (0, 4)        -0.125307347426
 (1, 4)        -1.46640871661
 (2, 4)        0.0108410499861
 (3, 4)        -2.0629227477
 (0, 5)        0.504493692248
 (1, 5)        1.42488646441
 (2, 5)        -2.08957962801
 (3, 5)        -1.29113629796
 (0, 6)        1.07289013113
 (1, 6)        0.0353266410166
 (2, 6)        -0.108999316299
 (3, 6)        -0.722534309773
c data after (coo_matrix): [ 0.80168251  0.45875588  0.72752298 -0.02555597
-1.39944231 -0.15916679
 1.34140445 -0.87197938  0.25345622 -0.42632756 -0.37043453 -0.76835675
 1.42371329  0.56484416  0.78127267  0.82776032 -0.12530735 -1.46640872
 0.01084105 -2.06292275  0.50449369  1.42488646 -2.08957963 -1.2911363
 1.07289013  0.03532664 -0.10899932 -0.72253431]


Best Regards,
Ergun

Ergun Biçici
http://bicici.github.com/ <http://ergunbicici.blogspot.com/>

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