3.2 Directed Parallelization Using the kf77 Driver and PCF Directives

Use directed parallelization if you are experienced with parallel programming, and you want to explicitly control which loops KAP parallelizes with PCF directives. PCF directives eliminate the need for you to write calls to directives.

In general, use PCF directives only with loops that are safe to parallelize. Where KAP sees loops prefaced with PCF directives, it does not perform data dependence analysis and does not prevent you from using a parallel directive incorrectly.

To compile a program with PCF directives for directed parallel execution, use the compiler and linker switches for your version of DIGITAL UNIX as follows:

DIGITAL UNIX Version 3.2:
```
kf77 myprog_pcf.f -lkmp_osf -threads
```
- -threads - causes KAP to link to POSIX 1003.4a/d4-compliant DECthreads library libpthreads.so .
- -lkmp_osf - causes KAP to link to the parallel processing library libkmp_osf.a .
DIGITAL UNIX Versions 4.0 and above:
```
kf77 myprog_pcf.f -lkmp_osfp10 -pthread
```
- -pthread - causes KAP to link to POSIX 1003.1c-compliant DECthreads library libpthread.so .
- -lkmp_osfp10 - causes KAP to link to the parallel processing library libkmp_osfp10.a .

Note

To determine the version of DIGITAL UNIX on your system, use the following cshell command:

uname -r

KAP provides the following PCF directives. Refer to the appropriate sections for explanations and code examples as follows:

C*KAP* ONE PROCESSOR SECTION . . . END ONE PROCESSOR
   SECTION

(See Section 3.2.7.)
C*KAP* PARALLEL REGION . . . END PARALLEL REGION (See Section 3.2.2.)
C*KAP* PARALLEL DO (See Section 3.2.3.)

C*KAP* CRITICAL SECTION . . . END CRITICAL
   SECTION

(See Section 3.2.6.)

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