Fortran 90 recommended on Crays

"More SCD consultants recommend Fortran 90."

Version 2 of Cray's Fortran 90 (f90) was installed on all the Cray machines on 18 May 1996. We recommend that you start to use f90 rather than cf77 because:

• f90 is now Cray's "officially supported" Fortran compiler.

• f90, Version 2 is much improved over Version 1 and is now comparable in performance to cf77.

• f90 has many nice, new features.

• Existing cf77 codes should work fine as is under f90.

To use the latest compilers (including f90, Version 2) and libraries, you will need to use Cray's new "Programming Environment." (See "New Cray package provides more integrated programming environment," in this issue.) To do this, you just need to add a few lines to your start-up files. (See the section "Fortran and C changes" in the article "User changes in UNICOS 9.0.2" for the required lines.) We recommend that all users start using the Programming Environment, whether or not you use f90.

Highlights of f90

• Here are some of the new features of f90:
  • Free-form source (optional)
  • New DO constructs (WHILE, CYCLE, EXIT)
  • CASE and WHERE constructs
  • Recursion
  • Modules
  • Data structures
  • Array processing
  • Internal procedures
  • Optional and keyword arguments
  • Non-advancing I/O
  • Allocatable arrays and pointers
  • Bit manipulation
  • New intrinsic functions

• The CF90 2.0 compiler is now equivalent in functionality and performance to the CF77 6.0.4 compiling system. Here are some of the equivalence features:
  • Conditional compilation preprocessing support
  • Runtime checking
  • Inlining of source code and array intrinsics
  • Bit Matrix Multiply support
  • Enhancement of optimization messages
  • Additional FPP directives recognized for increased tasking
  • Automatic scoping when tasking
  • No reassociation
  
  
• Performance has been improved to create execution equivalence for both unitasked and multitasked codes when compared to the CF77 compiling system. Here are some of the performance features:
  • Vector search and update loops
  • Enhanced CF90 unformatted I/O performance
  • Improved pattern matching
  • Tasking of single-nest and innermost loops
  • Array syntax vectorization at all optimization levels
  • Threshold testing for tasked loops
  
  
• Performance enhancements have been made for CF90 unformatted I/O.

• The shared cache, available with the ffio cache layer, is now multitask protected.

• Changes have been made to list-directed I/O after non-advancing writes.

• Changes have been included to make f90 list-directed output of a mixture of character and non-character items standard- conforming.

Other related commands

The f90 programming environment includes the compiler, libraries, and various tools, including:

atchop	dbx	jt	profview
atexpert	debug	jumpview	segldr
cdbx	debugview	perfdmp	totalview
cflint	f90	perfview	xbrowse
cflist	flowview	procview	xhelp
cifconv	gpp	prof

Documentation

• Man pages: There are man pages for all the commands (for example, man f90, man jumpview).

• Manuals: Manuals are available online via the craydoc facility on meeker.ucar.edu. The related manuals include:
  • SR-3901, CF90 Commands and Directives Reference Manual

  • SR-3902, Vol. 1, CF90 Fortran Language Reference Manual

  • SR-3903, Vol. 2, CF90 Fortran Language Reference Manual

  • SR-3905, Vol. 3, CF90 Fortran Language Reference Manual

  • SG-2192, Optimizing Code on Cray PVP Systems

  • SG-2168, Application Programmer's I/O Guide

  • IN-2167, Introducing CrayLibs

  • IN-2140, Introducing the Program Browser

  • IN-2502, Introducing the Cray TotalView Debugger

  • IN-2511, Introducing the MPP Apprentice Tool

  • SG-2182, Guide to Parallel Vector Applications

  • SR-2401, Compiler Information File (CIF) Reference Manual

  • 2091, UNICOS CDBX Symbolic Debugger Reference Manual

  • 2094, UNICOS CDBX Debugger User's Guide

• Books: There are numerous books on the market about Fortran 90.

• News files: Additional information can be found in these files in /usr/news:
  • CF9020.news
  • CrayLibs20.news
  • CrayTools20.news
  • PrgEnv.news

  Examples

  • f90 myprog.f  # Fixed format source (start in col. 7, etc.)
    a.out

  • f90 myprog.f90  # Free-format source
    a.out

  • f90 -r0 myprog.f  # Get program listing in myprog.lst
    a.out

  • f90 -o myprog myprog.f90  # Name the executable
    myprog

  • f90 -L /usr/local/lib -l nag myprog.f90   # Include nag library
    a.out

  • f90 -c myprog.f90    # Compile, but don't run segldr.

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