Convert Fortran 77 to Fortran 95

Question

I got a piece of code here and I can't seem to figure out an efficient way of converting this piece of code to the Fortran 95 equivalent. I have tried several things already, but I'm always stuck on making 1D arrays from matrices and the other way around (the point is to reduce calculation time, and if I convert them, I can't think of another way than using loops again :/).

This is the piece of code:

do i=1,dim
do j=1,dim
    Snorm(i,j)=Sval(j)/Sval(i)
    Bnorm(i,j)=Bval(j)/Bval(i)
    Pnorm(i,j)=Pval(j)/Pval(i)
enddo
enddo

How would you write that in Fortran95 code?

The equivalent of the matrix calculations in R is this:

Snorm <- t(Sval %*% t(1/Sval))
Bnorm <- t(Bval %*% t(1/Bval))
Pnorm <- t(Pval %*% t(1/Pval))

The equivalent of it in Python is this:

Snorm = (numpy.dot((Svalmat.T),(1/Svalmat))).T
Bnorm = (numpy.dot((Bvalmat.T),(1/Bvalmat))).T
Pnorm = (numpy.dot((Pvalmat.T),(1/Pvalmat))).T

with Svalmat etc the equivalent of Sval, but then columnmatrix 

Anyone has an idea?

Answer 1

It is not worth changing in my opinion. It is valid Fortran 95. Especially if your goal is the calculation time. Any "clever" tricks with subarrays can introduce array temporaries.

The obvious try is forall or do concurrent

forall(i=1:dim, j=1:dim)
    Snorm(i,j)=Sval(j)/Sval(i)
    Bnorm(i,j)=Bval(j)/Bval(i)
    Pnorm(i,j)=Pval(j)/Pval(i)
end forall

and the same with do concurrent.

Notice, that your original order of the loops is probably not efficient.