Keywords: slug

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## Checking the BLAS and BLACS Libraries

The best way to determine whether one is using efficient BLAS and BLACS libraries is to time them. ScaLAPACK provides a rudimentary BLAS and BLACS timer in the examples/timers directory on netlib and on the CD-ROM. This directory also contains pointers and instructions for more complete timers, such as the LAPACK BLAS timer and the message-passing benchmark program [46]. We encourage users to use these timers to measure the performance of the BLAS.

This ScaLAPACK examples/timers directory also contains pointers to some benchmark results and some pointers on interpreting the results of the timers.

To determine which BLAS and BLACS libraries are being linked in, users should check the output of the linker. If the `Makefile` includes `SLmake.inc`, the BLAS library is given by the macro BLASLIB in `SLmake.inc` while the BLACS library is given by the macro BLACSLIB. If the BLAS library name is of the form `blas_LINUX.a`, this is probably the (slow) reference implementation BLAS. If the BLAS library name is `-lblas`, `-lessl`, `-ldxml` or the like, this may be an optimized BLAS library.