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Barry,<br>
thank you for your reply. I only thought that there was a problem with
gcc and higher optimizations. I have for example a problem with gcc
4.6 as when I compile my program with -O3 the result would then not
converge any more. With the optimisation -O2 it works all well also
all other gcc I had before made no problems. So I thought as configure
set gcc with only -O and icc with -O3 there was generally a problem
with gcc and optimizations. But if not it is good.<br>
<br>
Manfred<br>
<br>
Barry Smith schrieb:
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type="cite">
<pre wrap=""> Manfred,
./configure is not smart enough to know what optimization flags are best for all compilers/systems. Thus we have relatively straightforward defaults. As Jed notes, if you know what flags are most appropriate for your build you must pass them in to ./configure
Barry
On May 8, 2012, at 7:59 AM, Jed Brown wrote:
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<pre wrap="">On Tue, May 8, 2012 at 1:32 AM, Manfred Gratt <a class="moz-txt-link-rfc2396E" href="mailto:manfred.gratt@uibk.ac.at"><manfred.gratt@uibk.ac.at></a> wrote:
when I compile petsc with --with-debugging=0 with gcc and icc in configure there are different optimization flags set depending on compiler. So is with gcc -O set wich means -O1 optimization. While with icc -O3 optimisation is set. Is there a reason only icc gets the high performance flag while gcc not? Are there any problems when some optimizations are activated on gcc?
I don't know why only -O1 is used with gcc, but you can pass COPTFLAGS='-O3 -march=native' or whatever you like to configure to make it use those instead.
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