HP aC++/HP C A.06.20 Programmer's Guide

• _POSIX_C_SOURCE=199506L

Required by pthread.

• libpthread.*

Kernel thread library used on 11.x systems

See “Using Threads” (page 211) for more information.

NOTE: Make sure that -mt is used consistently at compile and link times. When you

link with -mt, everything must be compiled with -mt, even if you do not think your

file will be used in a threaded application. When you incorrectly mix and match with

-mt, you get a runtime abort with the following message:

aCC runtime: Use of "-mt" must be consistent during both compilation and linking.

To find the library or object that is missing -mt, use /usr/ccs/bin/footprints

and look for the following:

-mt [(off) 1] -mt [on 1] (Or not present)

The number 1 above is the count of objects with that -mt setting. Not present implies

the source was not compiled with a recent compiler that contains this information.

+O[no]autopar

The +Oautopar option enables automatic parallelization of loops that are deemed safe

and profitable by the loop transformer.

Usage:

This optimization allows applications to exploit otherwise idle resources on multicore

or multiprocessor systems by automatically transforming serial loops into multithreaded

parallel code. When the +Oautopar option is used at optimization levels +O3 and

above, the compiler automatically parallelizes those loops that are deemed safe and

profitable by the loop transformer.

Automatic parallelization can be combined with manual parallelization through the

use of OpenMP directives and the +Oopenmp option. When both +Oopenmp and

+Oautopar options are specified, then any existing OpenMP directives take precedence,

and the compiler will only consider auto-parallelizing other loops that are not controlled

by those directives.

Programs compiled with the +Oautopar option require the libcps, libomp, and

libpthreads runtime support libraries to be present at both compilation and runtime.

When linking with the HP-UX B.11.61 linker, compiling with the +Oautoparoption

causes them to be automatically included. Older linkers require those libraries to be

specified explicitly or by compiling with +Oopenmp.

Parallel Processing Options 89