p?getrf and p?getri on sub matrix bug

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p?getrf and p?getri on sub matrix bug

Postby siegyoung » Sat Aug 03, 2013 10:04 pm

Dear Julien,

I looked into the source code of p?getrf and found this,

00178 IF( INFO.EQ.0 ) THEN
00179 IROFF = MOD( IA-1, DESCA( MB_ ) )
00180 ICOFF = MOD( JA-1, DESCA( NB_ ) )
00181 IF( IROFF.NE.0 ) THEN
00182 INFO = -4
00183 ELSE IF( ICOFF.NE.0 ) THEN
00184 INFO = -5

00185 ELSE IF( DESCA( MB_ ).NE.DESCA( NB_ ) ) THEN
00186 INFO = -(600+NB_)
00187 END IF
00188 END IF

I read the code as "you can only play with the sub matrix starting right at IA = x*blocksize + 1 and JA = y*blacksize + 1". Otherwise, iroff (or icoff) would not equal to 0 and the subroutine would exit and report its parameter 4(or 5) is illegal. Correct?

Regards,
Sieg
siegyoung
 
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Joined: Tue Jul 30, 2013 10:25 am

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