Thanks Tim, I thought that the gcc list was the most appropriate one
regarding the gomp implementation, but I'll post this question on the
gcc-help list.
By the way, Ubuntu 9.10 is the latest version (dd Oct. 2009). HTT works
fine for daily use, but massive parallel applications show some odd
behaviour:
Depending on the structure of the algorithm some pieces of code run
significantly faster (about 10%) with HTT enabled, while other pieces of
code run slower (some more than 50%). This slowdown happens due to
parallel sections inside loops...
Edwin
Tim Prince wrote:
On 2/11/2010 2:00 AM, Edwin Bennink wrote:
Dear gcc list,
I noticed that starting an OpenMP parallel section takes a
significant amount of time on Nehalem cpu's with hyper-threading
enabled.
If you think a question might be related to gcc, but don't know which
forum to use, gcc-help is more appropriate. As your question is
whether there is a way to avoid anomalous behaviors when an old Ubuntu
is run on a CPU released after that version of Ubuntu, an Ubuntu forum
might be more appropriate. A usual way is to shut off HyperThreading
in the BIOS when running on a distro which has trouble with it. I do
find your observation interesting.
As far as I know, the oldest distro which works well on Core I7 is
RHEL5.2 x86_64, which I run, with updated gcc and binutils, and HT
disabled, as I never run applications which could benefit from HT.
