Separate Focus HTML for Basic Foil 4 Why is Fortran90 Easier than Fortran77

Basic HTML version of Foils prepared 17 Sept 1996

Foil 4 Why is Fortran90 Easier than Fortran77

From New CPS615HPF and Fortran90 Discussion Sept 17 96 Basic Simulation Track for Computational Science CPS615 -- Fall Semester 96. by Geoffrey C. Fox, Tom Haupt

Do 1 I=1,N

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.