Compiler option defaults

Compilations most commonly occur on the Front End Node. The resulting program can run on the Blue Gene/L system without manually copying the executable to the Service Node. See the "Running Applications" topic in section 5.1 of the Blue Gene/L Application Development document to learn how to run programs on Blue Gene/L.

The blrts_* compiler invocation commands set certain default compiler options to maximize the use of the Blue Gene architecture.

-qarch=[440d | 440]

Arguments

Specifies which instructions the compiler can generate. Suboptions include:

440
Generates code for the single floating-point unit (FPU) only.
440d
Generates parallel instructions for the 440d Double Hummer dual FPU. This is the default. Note that if you encounter problems with code generation, try resetting this option to -qarch=440.
Note:
The Double Hummer FPU does not generate exceptions. The -qflttrap option, which traps floating-point exceptions, is disabled by default. If you enable the -qflttrap option, -qarch is automatically reset to -qarch=440.

-qbgl

Marks the object file as standalone to run on Blue Gene/L.

-qnoautoconfig

Prevents optimization levels -O4 and -O5 from resetting the -qarch setting to auto, thereby preserving the -qarch setting for the target architecture. This allows for cross-compilation to other architectures, such as Blue Gene.

-qtune=440

Optimizes code for the 440 family of processors. This is the default for -qarch=440 and -qarch=440d.