High Performance Fortran: history, overview and current developments

Processors as rectilinear mesh Physical Processors ALIGN REALIGN DISTRIBUTE REDISTRIBUTE Figure 1: HPF data mapping model The essential idea is that the relative alignment between two data objects may be defined --- typically by relations involving array elements. A group of aligned objects (arrays) are then distributed onto an abstract rectilinear grid of processors. The mapping of abstract to physical processors is implementation dependent. In figure 2 the arrays A and B are aligned with respect to each other so that A(I+1,J+1) and B(I,J) are aligned. The ALIGN directive is used to specify the alignment between objects. In figure 3 we show some potential distributions of the arrays A and B onto a set of 4 (abstract) processors. We are displaying axis 1 vertically and axis 2 horizontally. For the distribution (BLOCK,*) axis 1 REAL A(16,16),B(14,14) A B !HPF$ ALIGN B(I,J) WITH A(I+1,J+1) Figure 2: Array Alignment (BLOCK,*) (*,BLOCK) (BLOCK,BLOCK) P1 P2 P3 P4 P1 P2 P3 P4 P1 P2 P3 P4 ..