Fortran 90 Further Development, QUB

Further
Development

Fortran 95

Corrections to Fortran 90
FORALL

 FORALL (i = 1:n, j = 1:n, y(i, j) /= 0 .AND. i /= j) &

  x(i, j) = 1.0 / y(i, j)

 FORALL (i = 1:n)

  a(i, i) = i

  b(i) = i*I

 END FORALL

PURE attribute - make PURE procedures safe for use in FORALL statement
CPU time - CALL CPU_TIME(t1)
Also allocatable dummy arguments and results
Nested WHERE

 WHERE (mask1)

  ...

  WHERE (mask2)

   ...

  ELSEWHERE

   ...

  ENDWHERE

 ELSEWHERE

  ...

 ENDWHERE

Initial pointer or type default status

REAL, POINTER :: p(:) => NULL()

 TYPE string

  CHARACTER, POINTER :: ch(:) => NULL()

 ENDTYPE

Further development

With FORTRAN 90 barely out of cradle,
why are there already efforts to enhance it?

The limelight of HPC research has recently shifted away from vector computers and towards parallel and "massive" parallel computers
Fortran 90 may be suitable for HPC on conventional and vector computers, but it does not include features to obtain the best performance on parallel systems.
Demands for such features has led to the development of two de facto standards:
- High Performance Fortran (HPF)
- Message Passing Interface (MPI)

HPF

Goals

HPF provides a set of language extensions to Fortran 90 to support:

Data parallel programming
Top performance on MIMD and SIMD computers with non-uniform memory access
Code tuning for various architectures
Minimal deviation from other standards
Define open interfaces to other languages

What is in it

Compiler directives for data alignment and distribution
Concurrent execution features using the FORALL statement
A number of intrinsic functions to enquire about machine specific details
A number of extrinsic functions which provide an escape mechanism from HPF
A library of routines to support global operations

MPI

What

Message Passing Interface is a proposed standard for:

Explicit message passing
Application programs
MIMD distributed memory concurrent computers
Workstation networks

Why

Portability and ease-of-use
Time right for standard
Library construction
Prerequisite for development of concurrent software industry
Provides hardware vendors with well-defined set of routines that they must implement efficiently

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Maintained by Alan Rea, email A.Rea@qub.ac.uk

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