describes use of Fortran dummy arrays before Fortran IV. No LDA/B/C in the example provided. But I find it hard to believe that once a compiler existed that would compile that example, people took more than a week to realize that by adding LDA/B/C you can write a general DGEMM that can multiply submatrices.
We need to remember that first there was a compiler implementation and the language was secondary to that. Language extensions that the compiler could do "easily" get implemented quickly. Sequence association was one of those things and I still maintain that it would be needed (in the absence of array expressions) even if there was dynamic allocation in Fortran I.
Consider a subroutine that is expected to take the 1st column and the last column of an array, sum them, and put the result in the 1st column. You want to write
Can you reuse sub to only sum the bottom half of the columns? Not without allocating a new array and copying before passing the copy to sub. With sequence association, LDA and adjustable or assumed-size arrays and extra integer arguments, you can and it will work for any rank.
The alternative coding that I have seen (and abhor), is putting an LDA in a COMMON and then all your subroutines pick up an LDA from there. Such codes are usually riddled with errors.
describes use of Fortran dummy arrays before Fortran IV. No LDA/B/C in the example provided. But I find it hard to believe that once a compiler existed that would compile that example, people took more than a week to realize that by adding LDA/B/C you can write a general DGEMM that can multiply submatrices.
We need to remember that first there was a compiler implementation and the language was secondary to that. Language extensions that the compiler could do "easily" get implemented quickly. Sequence association was one of those things and I still maintain that it would be needed (in the absence of array expressions) even if there was dynamic allocation in Fortran I.
Consider a subroutine that is expected to take the 1st column and the last column of an array, sum them, and put the result in the 1st column. You want to write
allocate(a(3,5),source=b); call sub(a) deallocate(a) allocate(a(2,4),source=c); call sub(a)
Can you reuse sub to only sum the bottom half of the columns? Not without allocating a new array and copying before passing the copy to sub. With sequence association, LDA and adjustable or assumed-size arrays and extra integer arguments, you can and it will work for any rank.
The alternative coding that I have seen (and abhor), is putting an LDA in a COMMON and then all your subroutines pick up an LDA from there. Such codes are usually riddled with errors.