performance degradation with ifort 15.0.2

[Wentao_Z_]

Hi,

Previously I built my program with ifort 14.0.1 + impi 4.1. Recently, after switching to ifort 15.0.2 + impi 5.0, my program runs ~30% slower on one SandyBridge core. I keep the compiler options the same: -O2 -xHost -openmp. Anyone observed similar things? Any suggestions? 

Thanks!

Best regards,
   Wentao

[jimdempseyatthecove]

Can you link ifort 15.0.2 with impi 4.1 to ascertain if the problem is with the ifort compiler or with the impi library?

Jim Dempsey

[jimdempseyatthecove]

Note, faster is not necessarily better (faster with bug is not better than slower with bug fix).

[Wentao_Z_]

jimdempseyatthecove wrote:

Can you link ifort 15.0.2 with impi 4.1 to ascertain if the problem is with the ifort compiler or with the impi library?

Jim Dempsey

Hi Jim,

Thanks for your quick response. Right now I am not able to try that ... (I am using a big cluster Stampede@TACC, it will automatically give me impi 5 if I load ifort 15). But I am just testing on serial runs so there should be very few MPI calls involved.

Best regards,
   Wentao

[Wentao_Z_]

jimdempseyatthecove wrote:

Note, faster is not necessarily better (faster with bug is not better than slower with bug fix).

That is true:-)