Vector Update: Loop Interchange

• To interchange the loops they have to be properly nested

  • substitution expressions and eliminating temporary variables
  • now the loops can be interchanged

do jj=1,nj

do ii=1,ni

res=0

do n=1,nib

ndb1=nmb1/2

naa1=nma1+ii+(n-1)*nra+(i-1)*nru+(l-1)*nra*nrub

nbb1=ndb1+n+(jj-1)*nib

res=res+p(naa1)*dp(nbb1)

end do

nde1=nme1/2

lle1=nde1+ii+(jj-1)*ni

dp(lle1)=dp(lle1)+res

end do

end do

res can be eliminated by placing

in inner loop

do jj=1,nj

do ii=1,ni

do n=1,nib

ndb1=nmb1/2

naa1=nma1+ii+(n-1)*nra+(i-1)*nru+(l-1)*nra*nrub

nbb1=ndb1+n+(jj-1)*nib

nde1=nme1/2

lle1=nde1+ii+(jj-1)*ni

dp(lle1)=dp(lle1)+p(naa1)*dp(nbb1)

end do

end do

end do

Previous slide

Next slide

Back to first slide

View graphic version