Hello everyone

I've noticed that order of loops in xGETC2 is not optimal. It goes through the rows of matrix. But our matrices have column layout. Is not it better to change the order of loops, so we get more cache friendly algorithm?

It can cause difference in case, if we have two equal maximum elements in matrix, so we get different LU decomposition and different ipiv/jpiv arrays. But it seems, that both of this results should be correct

For example, see SRC/sgetc2.f, lines 178-187:

XMAX = ZERO 
DO 20 IP = I, N
    DO 10 JP = I, N
        IF( ABS( A( IP, JP ) ).GE.XMAX ) THEN
            XMAX = ABS( A( IP, JP ) )
            IPV = IP
            JPV = JP
        END IF
    CONTINUE
CONTINUE

Changing the order of loops makes IP continuous index, and cache works better