-qcache

The -qcache argument specifies the cache configuration of the processor on which the program will be run. The argument must be used in combination with the -O4, -O5, or -qipa options with a C or C++ compile and in combination with the -qhot option with a Fortran compile. The compiler uses the information provided by this argument to determine how loop operations can be structured or blocked to process only the amount of data that can fit into the data cache. The default value for this argument is the same as that of the -qtune option.

As with -qtune, a code compiled with this argument designated for one type of processor will run correctly on any other POWER or POWERPC processor, although its performance may be worse than it would be if it were compiled with the appropriate -qcache argument.

This option is designed for those cases in which the cache on the processor on which the code will be run is different from the standard cache for that processor.

If this argument is used in a compile, NERSC recommends it be given this value:

      -qcache=auto

The -qcache=auto option tells the compiler to produce a program for the cache configuration of the processor on which it is compiled.