I am having a problem getting my scientific modeling code to run on RHEL 4.1 x86-64. I am using version 6.05 of the PGI fortran compiler.
The code crashes with a memory fault when compiled with optimization as a 64bit application on RHEL 4.1 x86-64.
The code compiles and runs WITHOUT optimization with some (but not all) compiler options as a 64 bit application on RHEL 4.1 x86-64
The code compiles and runs with and without optimization on 32bit RHEL V3.5 or V4.1
The code compiles and runs with and without optimization as a 32 bit application under RHEL 4.1 x86-64. Performance is poor in this case.
Data in memory appears to be corrupted. Similar to what might be seen with array out of bounds errors but no array addressing errors were found in the non-optimized 64 bit case. The compiler options and machine characteristics are listed below.
AMD64 X2 - 4600+ - 2Gb RAM
RHEL 4.1 x86-64
pgf90 6.0-5 64-bit target on x86-64 Linux
OPTG= -g -Mlist -Mdclchk -Mdepchk -Mfptrap -Minfo -Mbounds
Program runs apparently ok.
OPTG= -g -Mlist -Mdclchk -Mdepchk -Mfptrap -Minfo -Mbounds -Mchkstk -Mchkptr -Mchkfpstk
Program crashes with an array out of bounds error. Addition of the -Mchkstk -Mchkptr -Mchkfpstk options causes the array bounds error since it was not present with the first set of options.
OPTO= -O -Mlist
Program crashes with a memory fault.
Looking at the optimized failure. An integer value in memory is changed unexpectedly - the code between these two outputs is an small fortran subroutine with no direct access to global variables - the subroutine does call two routines written in C.
The problem could not be replicated when a smaller subset of code was extracted containing only the intervening code between these two statements.
Adding the following statement at the end of the intervening fortran routine:
Results in the following:
Addition of the write statement eliminated the memory corruption somehow. However, additional memory corruption problems surface later in code execution with the optimized 64 bit version of the executable - and I don’t trust any workaround where adding a write statement apparently solves the problem …
I can also get elimiate the array bounds error in the non-optimized failure case by adding write statements to the code …
Any suggestions or ideas?