On Mon, 09 Apr 2007 05:48:07 +0400, maxim wexler <[EMAIL PROTECTED]>
wrote:
Hi group,
I note two schools of thought on the best CFLAGS for
the Pentium III processor.
One suggests using -O3 -pipe, the other, -O2 without
the pipe.
How much difference does this make? Is the extra level
of optimization with pipe the equivalent of the lower
level without?
Man gcc. -pipe allows to use pipes (memory) instead of temporary files
(disk). -O controls the resulting binary sometimes making it fast, large,
and unreliable. I have seen ebuilds that enforce -O2 even when -O3 is
specified. This can create a faulty impression that -O3 always works fine.
-O and -pipe interact through the size of temporary files. Theoretically,
-pipes may slow down compiles if there is not enough memory. Another
factor that should be taken into account is the number of threads for
make. For a PIII machine the generally recommended number is 2, but when
the RAM is limited, say 384 megs, 1 thread with pipes works better.
Ideally you should measure compile times for large projects like Open
Office and find out what works best on your system. I would start with 1
thread -O2 and -pipe.
--
Andrei Gerasimenko
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