Rebuilding using an earlier version of the compiler

[Joe2]

This question is about rebuilding code using a version of the Intel Visual Fortran compiler which is different from the one originally used. Some colleagues provide us with an executable file and its Fortran source code. We generally need to make minor changes to the source code and then re-build to create a slightly amended executable. This has worked fine in the past, but we have recently found that in some circumstances our re-built executable has significantly longer run-times than the original executable (e.g. one day instead of one hour). We observe the same problem even if we re-build without making any changes to the code and even though we use the same Visual Studio settings as our colleagues. We believe that the cause of the problem may be that we and our colleagues are now using different versions of the Intel Visual Fortran Compiler (we use v11.0 of the Intel Visual Fortran Compiler with Visual Studio 2008; they use v13.0 of the Intel Visual Fortran Compiler with Visual Studio 2010). My question has two parts:- (1) Are we correct in thinking that that the most likely cause of the problem is the fact that we are using v11.0 of the compiler whereas our colleagues are using v13.0? (2) If the answer to part (1) is “yes”, then what is the best way for us to solve the problem? If we upgrade our Fortran compiler, do we need to upgrade to v13.0 (i.e. the same version as our colleagues are using), or will upgrading to the most recent version of the compiler be okay (even though it will be different from the version being used by our colleagues)?

[TimP]

If your optimization flags are the same as your colleague's, it's possible that you encountered a missed optimization in the older compiler.  Usually, a newer compiler would do at least as well as an older one.  A current compiler would have the advantage that you could file a support issue if you should continue to have difficulty.  If your application requires Visual Studio, the current ifort requires at least VS2010.

[Steven_L_Intel1]

Rebuilding with a later version should be fine.