Installing SECOND and DSECND

Both the timing routines and the test routines call SECOND (DSECND), a real function with no arguments that returns the time in seconds from some fixed starting time. Our version of this routine returns only ``user time'', and not ``user time 10#10 system time''. The version of SECOND in second.f calls ETIME, a Fortran library routine available on some computer systems. If ETIME is not available or a better local timing function exists, you will have to provide the correct interface to SECOND and DSECND on your machine.

On some IBM architectures such as IBM RS/6000s, the timing function ETIME is instead called ETIME_, and therefore the routines LAPACK/INSTALL/second.f and LAPACK/INSTALL/dsecnd.f should be modified. Usually on HPPA architectures, the compiler and loader flag +U77 should be included to access the function ETIME.

The test program in secondtst.f performs a million operations using 5000 iterations of the SAXPY operation 11#11 on a vector of length 100. The total time and megaflops for this test is reported, then the operation is repeated including a call to SECOND on each of the 5000 iterations to determine the overhead due to calling SECOND. The test program executable is called testsecond (or testdsecnd). There is no single right answer, but the times in seconds should be positive and the megaflop ratios should be appropriate for your machine. The files second.f and dsecnd.f are automatically copied to LAPACK/SRC/ for inclusion in the LAPACK library.