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If you suspect a BLAS-related problem and you are linking with an optimized version of the BLAS, we would strongly suggest as a first step that you link to the Fortran 77 version of the suspected BLAS routine and see if the error has disappeared.

We have included test programs for the Level 1 BLAS. Users should therefore beware of a common problem in machine-specific implementations of xNRM2, the function to compute the 2-norm of a vector. The Fortran version of xNRM2 avoids underflow or overflow by scaling intermediate results, but some library versions of xNRM2 are not so careful about scaling. If xNRM2 is implemented without scaling intermediate results, some of the LAPACK test ratios may be unusually high, or a floating point exception may occur in the problems scaled near underflow or overflow. The solution to these problems is to link the Fortran version of xNRM2 with the test program. On some CRAY architectures, the Fortran77 version of xNRM2 should be used.

Julie Langou 2007-02-26