Basic HTML version of Foils prepared 26 September 1996

Foil 16 Why is Fortran90 Easier than Fortran77

From HPCC Software Technologies Fall 96 -- Overview and HPF Delivered Lectures of CPS615 Basic Simulation Track for Computational Science -- 26 September 96. by Geoffrey C. Fox


1 1 A(I)=B(I) is obviously parallel
2 Fortran90 Array Notation
  • A=B expresses this parallelism naturally in way compiler can easily detect in a deterministic way
  • Do 1 I=1,N
  • J=I
  • K=I
3 1 A(J)=B(K) is not so obviously parallel
4 Needs a difficult to define (in general case) algorithm (especially if IF statements, i.e. conditionals, defining I,J) to decide on existence and implementation of parallelism
5 Use of Fortran77 has "thrown away" natural parallelism at language level even though "run-time" restores as creates explicit values for variables such as J and K which are only known by analysis at compile time.

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