I have a speed up problem using 4 threads on quadcore system. With 2 threads the efficiency is close to 1 but with 4 threads it reduces to half that is the running time is more or less same as when running the code using 2 threads. I searched this forum and i find similar issue before which is because of Inter turbo boost technology. Please refer to this post viewtopic.php?f=3&t=1289&start=0&hilit=intel+turbo+boost
So i have tried to disable turbo boost on all the 4 processors of my machine but couldn't get rid of the problem.
I took the benchmark code from above link only.
I have a DELL laptop and my harware/OS information summary is as follows:
OS : Linux126.96.36.199-generic , Ubuntu
KDE SC Version : 4.7.1
Processor: Intel(R) Core(TM) i7-2620M CPU @ 2.70GHz
Please let me know what could be other possible problems that is not allowing me to speed up using 4 threads/cores. As an additional info. i have checked that all the 4 threads are running on different cores.
Looking forward to your answers.