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###

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.

** Next:** Testing IEEE arithmetic and
** Up:** Test and Install the
** Previous:** Installing SLAMCH and DLAMCH
** Contents**
Susan Blackford
2001-08-13