Fortran Programming Guide

Chapter 1

Introduction

The Sun Fortran compilers, f77 and f95, described in this book (and the companion book Sun Fortran User's Guide) are available under the Solaris operating environment on the various hardware platforms that Solaris supports. The compilers themselves conform to published Fortran language standards, and provide many extended features, including multiprocessor parallelization, sophisticated optimized code compilation, and mixed C/Fortran language support.

The compilers are components of the Sun Performance WorkShop^TM 6. The Fortran 90 compiler, f90, of previous releases of the Sun Performance WorkShop has been renamed f95 in Sun WorkShop 6. The f90 command is now an alias for f95 -- both invoke the Sun Performance WorkShop 6 Fortran 95 compiler.

Standards Conformance

• f77 was designed to be compatible with the ANSI X3.9-1978 Fortran standard and the corresponding International Organization for Standardization (ISO) 1539-1980, as well as standards FIPS 69-1, BS 6832, and MIL-STD-1753.
• f95 was designed to be compatible with the ANSI X3.198-1992, ISO/IEC 1539:1991, and ISO/IEC 1539:1997 standards documents.
• Floating-point arithmetic for both compilers is based on IEEE standard 754-1985, and international standard IEC 60559:1989.
• On SPARC platforms, both compilers provide support for the optimization-exploiting features of SPARC V8, and SPARC V9, including the UltraSPARC^TM implementation. These features are defined in the SPARC Architecture Manuals, Version 8 (ISBN 0-13-825001-4), and Version 9 (ISBN 0-13-099227-5), published by Prentice-Hall for SPARC International.
• In this document, "Standard" means conforming to the versions of the standards listed above. "Non-standard" or "Extension" refers to features that go beyond these versions of these standards.

The responsible standards bodies may revise these standards from time to time. The versions of the applicable standards to which these compilers conform may be revised or replaced, resulting in features in future releases of the Sun Fortran compilers that create incompatibilities with earlier releases.

Features of the Fortran Compilers

Sun Fortran compilers provide the following features or extensions:

• f77: Global program checking across routines for consistency of arguments, commons, parameters, and the like.
• SPARC only: Support for multiprocessor systems, including automatic and explicit loop parallelization, is integrated tightly with optimization.

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  Note – Parallelization features of the Fortran compilers require a Sun WorkShop HPC license.

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• f77: Many VAX/VMS Fortran 5.0 extensions, including:
  
  
  • NAMELIST
    
  • DO WHILE
    
  • Structures, records, unions, maps
    
  • Variable format expressions
    
  • Recursion
    
  • Pointers
    
  • Double-precision complex
    
  • SPARC: Quadruple-precision real
    
  • SPARC: Quadruple-precision complex
• Cray-style parallelization directives, including TASK COMMON, with extensions for f95.
• OpenMP parallelization directives accepted by f95.
• Global, peephole, and potential parallelization optimizations produce high performance applications. Benchmarks show that optimized applications can run significantly faster when compared to unoptimized code.
• Common calling conventions on Solaris systems permit routines written in C or C++ to be combined with Fortran programs.
• Support for 64-bit Solaris environments on UltraSPARC platforms.
• Call-by-value, %VAL, implemented in both f77 and f95.
• Interoperability between Fortran 77 and Fortran 95 programs and object binaries.
• Interval Arithmetic expressions in f95.

Other Fortran Utilities

The following utilities provide assistance in the development of software programs in Fortran:

• Sun WorkShop Performance Analyzer -- In depth performance analysis tool for single threaded and multi-threaded applications. See analyzer(1).
• asa -- This Solaris utility is a Fortran output filter for printing files that have Fortran carriage-control characters in column one. Use asa to transform files formatted with Fortran carriage-control conventions into files formatted according to UNIX line-printer conventions. See asa(1).
• fpp -- A Fortran source code preprocessor. See fpp(1).
• fsplit -- This utility splits one Fortran file of several routines into several files, each with one routine per file. Use fsplit on FORTRAN 77 or Fortran 95 source files. See fsplit(1)

Debugging Utilities

The following debugging utilities are available:

• error -- (f77 only) A utility to merge compiler error messages with the Fortran 77 source file. (This utility is included if you do a developer install, rather than an end user install of Solaris; it is also included if you install the SUNWbtool package.)
• -Xlist --A compiler option to check across routines for consistency of arguments, COMMON blocks, and so on.
• Sun WorkShop --Provides a visual debugging environment based on dbx and includes a data visualizer and performance data collector.

Sun Performance Library

The Sun Performance Library^TM is a library of optimized subroutines and functions for computational linear algebra and Fourier transforms. It is based on the standard libraries LAPACK, BLAS, FFTPACK, VFFTPACK, and LINPACK.

Each subprogram in the Sun Performance Library performs the same operation and has the same interface as the standard library versions, but is generally much faster and possibly more accurate.

See the performance_library README file, and the Sun Performance Library User's Guide for details.

Interval Arithmetic

This release of the Fortran 95 compiler introduces two new compiler flags, -xia and -xinterval that enable the compiler to recognize new language extensions and generate the appropriate code to implement interval arithmetic computations.

See the Interval Arithmetic Programming Reference for details.

Man Pages

On-line manual (man) pages provide immediate documentation about a command, function, subroutine, or collection of such things.

Sun WorkShop man pages are located in install_directory/SUNWspro/man/. (In a normal install of the Sun WorkShop, install_directory is /opt.) Add this path to your MANPATH environment variable to access these Sun WorkShop man pages. (See the Fortran User's Guide for details.)

You can display a man page by running the command:

demo% man topic

Throughout the Fortran documentation, man page references appear with the topic name and man section number: f77(1) is accessed with man f77. Other sections, denoted by ieee_flags(3M) for example, are accessed using the -s option on the man command:

demo% man -s 3M ieee_flags

Man pages for the Fortran library routines are found in section 3F.

The following lists man pages of interest to Fortran user:

f77(1) and f95(1)	The Fortran compilers command-line options
analyzer(1)	Sun WorkShop Performance Analyzer
asa(1)	Fortran carriage-control print output post-processor
dbx(1)	Command-line interactive debugger
fpp(1)	Fortran source code pre-processor
cpp(1)	C source code pre-processor
fsplit(1)	Pre-processor splits Fortran 77 routines into single files
ieee_flags(3M)	Examine, set, or clear floating-point exception bits
ieee_handler(3M)	Handle floating-point exceptions
matherr(3M)	Math library error handling routine
ild(1)	Incremental link editor for object files
ld(1)	Link editor for object files

READMEs

The READMEs directory contains files that describe new features, software incompatibilities, bugs, and information that was discovered after the manuals were printed. The location of this directory depends on where your software was installed. The path is: install_directory/SUNWspro/READMEs/. In a normal install, install_directory is /opt.     

TABLE 1-1   READMEs of Interest

README File	Describes...
fortran_77	new and changed features, known limitations, documentation errata for this release of the FORTRAN 77 compiler, f77.
fortran_95	new and changed features, known limitations, documentation errata for this release of the Fortran 95 compiler, f95.
fpp_readme	overview of fpp features and capabilities
interval_arithmetic	overview of the interval arithmetic features in f95
math_libraries	optimized and specialized math libraries available.
profiling_tools	using the performance profiling tools, prof, gprof, and tcov.
runtime_libraries	libraries and executables that can be redistributed under the terms of the End User License.
64bit_Compilers	compiling for 64-bit Solaris operating environments.
performance_library	overview of the Sun Performance Library

The READMEs for all compilers are easily accessed by the -xhelp=readme command-line option. For example, the command:

f95 -xhelp=readme

will display the fortran_95 README file directly.

Command-Line Help

You can view very brief descriptions of the f77 and f90 command line options by invoking the compiler's -help option as shown below:

%f77 -help -or- f95 -help _______________________________________________________________ Items within [ ] are optional. Items within < > are variable parameters.Bar | indicates choice of literal values. For example: -someoption[=<yes|no>] implies -someoption is    -someoption=yes _______________________________________________________________ -a:            Collect data for tcov basic block profiling                    (old format) -ansi:         Report non-ANSI extensions. -arg=local:    Preserve actual arguments over ENTRY statements -autopar:      Enable automatic loop parallelization                        (requires WorkShop license) -Bdynamic:     Allow dynamic linking -Bstatic:      Require static linking -c:            Compile only - produce .o files, suppress linking -C:            Enable runtime subscript range checking -cg89:         Generate code for generic SPARC V7 architecture -cg92:         Generate code for SPARC V8 architecture -copyargs:     Allow assignment to constant arguments ...etc.