PROGRAM matmult
implicit none
!! Declarations
! Define 3 allocatable 2-dimensional integer arrays
! and any temporary variables that you need
integer, dimension (:,:), allocatable :: array1
integer, dimension (:,:), allocatable :: array2
integer, dimension (:,:), allocatable :: array3
integer, dimension (:), allocatable :: printarray
integer :: l, m, n
integer :: i, j
integer :: temp, x
!! Create and initialize arrays
! Prompt for 3 integers (call them L, M, and N)
! They represent the dimensions of the arrays
! The first array will be dimension L x M, the second will be M x N
! and the product array, L x N
write(*,*) 'Enter array dimensions'
read(*,*) l, m, n
! Allocate the 3 arrays of the correct size
allocate (array1(l,m))
allocate (array2(m,n))
allocate (array3(l,n))
!! Initialize arrays
! Initialize the first array such that array(i,j) = 10i+j
do i = 1, m
do j = 1, l
array1(i, j) = (10*i)+j
end do
end do
! Initialize the second array such that array(i,j) = 20i+2j
do i = 1, n
do j = 1, m
array2(i, j) = (20*i)+(2*j)
end do
end do
! Multiply arrays
! Matrix multiplication C = AB
! C(i,j) = the sum product of row i of A and column j of B
do i = 1, n
do j = 1, l
temp = 0
do x = 1, n
temp = temp + array1(j,x) * array2(x,j)
end do
array3(i, j) = temp
end do
end do
! Print the array row-by-row to STDOUT (terminal)
! To print elements of an array in a row, you can define a loop as part of the WRITE
! Assuming that vec is a one-dimensional array of length 5 and j is a declared variable,
! the following will print that vector as a row
! WRITE(*,*) (vec(j), j=1, 5)
allocate(printarray(l))
do i = 1, n
do j = 1, l
printarray(j) = array3(j, i)
end do
write(*,*) printarray
end do
! Deallocate arrays
! If you allocate it, you need to deallocate it
deallocate(array1)
deallocate(array2)
deallocate(array3)
deallocate(printarray)
END PROGRAM matmult
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