SPEC Flag Description for the Cray C/C++/Fortran Compiler

Sections

Selecting one of the following will take you directly to that section:

Portability Flags
Compiler Flags

Portability Flags

"-f free"
-hc99
-hpic
-hdynamic

- "-f free"
- -f\ free(?=\s|$)
- Specify the layout used by the source file is free form.
- -hc99
- -hc.*(?=\s|$)
- enable language support for , as described below c99 enable C99 support for C programs c++0x enable preliminary support for some C++0x features
- -hpic
- -hpic
- Generates position independent code (PIC), which allows a virtual address change from one process to another, as is necessary in the case of shared, dynamically linked objects. The virtual addresses of the instructions and data in PIC code are not known until dynamic link time.
- -hdynamic
- -hdynamic
- Directs the compiler driver to link dynamic libraries at runtime. This option is used to create dynamically linked executable files and may not be used with the -h static or -h shared options. Note that the preferred invocation is to call the generic CC command with the -dynamic option, rather than using this compiler specific option.

Compiler Flags

- cc
- ^cc(?=\s|$)
- Invoke the Cray C compiler
- CC
- ^CC(?=\s|$)
- Invoke the Cray C++ compiler
- ftn
- ftn(?=\s|$)
- Invoke the Cray Fortran compiler

Shell, Environment, and Other Software Settings

OMP_THREAD_STACK_SIZE

Cray-specific, nonstandard variable used to change the size of the thread stack from the default size of 16 MB to the specified size. The number in unit of Byte.

OMP_SCHEDULE

For loops running with OpenMP schedule "static", this results in (#iterations/#threads) iterations--rounded to the next lower integer--being allocated to most threads, with at most one additional iteration being allocated to some threads. Although the largest number of iterations assigned to any thread remains the same, this results in a more even sharing of iterations between threads, which may sometimes lead to a performance improvement relative to the default static thread distribution.

OMP_DYNAMIC

OMP_DYNAMIC=[ 1 | 0 ] Enables (1) or disables (0) the dynamic adjustment of the number of threads.

OMP_NESTED

Enables (TRUE) or disables (FALSE) nested parallelism.

OMP_LIBRARY

Selects the OpenMP run-time library.

Set stack size to unlimited

The command "ulimit -s unlimited" is used to set the stack size limit to unlimited.