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[Help-gsl] gsl blas idamax

From: Andrew Makhorin
Subject: [Help-gsl] gsl blas idamax
Date: Sun, 26 May 2013 21:15:04 +0400


Maybe some one could help me.

If I call gsl blas idamax as follows:

   double x[3] = { 11, 33, 22 };
   . . .
   i = cblas_idamax(3, x, 1);

then which returned value is correct, 1 or 2 ? Gsl blas idamax returns
1 that corresponds to 0-base indexing. However, AFAIK, some C blas
implementations (e.g. IBM ESSL) follow Fortran conventions; otherwise,
the standard blas tests would fail.

I also would like to note that in case of n = 0 gsl blas idamax
(see blas/source_iamax_r.h) returns 0 rather than -1. Probably it is
a bug, since the reference Fortran version of idamax returns 0 in this


Andrew Makhorin

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