RE: I686 DOUBLE ALIGNMENT VS PERFORMANCE -Reply

[tprince at cat dot e-mail dot com]

Livermore Kernel source at:

http://www.llnl.gov/asci_benchmarks/asci/limited/lfk/README.ht
ml

appears to be the most up to date official version.  It does a
better job than earlier versions in figuring out how many times it
needs to go to get accurate timing results, as well as generating
check-sums which don't vary with the number of iterations.  The
check-sums, however, are simply the results achieved on typical
SGI machines, not an accurate reference (g77 on Intel is more
accurate).  It takes over half an hour to run on machines with
marginal timer calls.

I'll post my version with check-sums accurate to 17 digits (yes,
run on SGI in REAL*16), and some cleaned up loops, as
well as everything formatted into g77/f90 compatible code, if you
care to remind me at  tprince@computer.org.  This one, of
course, can't be compared with the results from the official one,
as I have fixed the gnu-unfriendly peculiarities.

I must apologize; further investigation turned up some failures to
build certain copies of egcs fully, as well as discrepancies
between timings obtained on Linux and cygwin32 on the same
machine.   Some of these weren't evident until I used this current
version of lfk and worked on building timers based on the Intel
TSC (WinAPI QueryPerformance), which isn't used by standard
egcs or g77.  Also, neither the binutils install nor gmake work on
Windows95, leaving some unreliable manual copying to do.

Might we be able to find a consensus on how clock(),
system_clock(), cpu_time() should be done on various Intel
OS's?  The current clock() and cpu_time() give 0.010 second
resolution on Linux and NT, but several of the timers have 1
second resolution under Windows95.  That could make this
benchmark run over a day trying to find repeatable timings, if it
didn't give up.

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