MatrMul

program MatrMul

   implicit none

   Character(len = 1) :: finishProgram
   integer :: n, i, j, k, maxDimension
   integer :: alloc_status, dealloc_status
   double precision, allocatable, dimension(:,:) :: a, b, c
   real :: t1, t2

   write ( *, * ) 'Maximun Dimension (Starts at 100, counting step 100): '
   read (*,*) maxDimension

   do n = 100, maxDimension, 100

      allocate(a(n,n),stat=alloc_status)
      allocate(b(n,n),stat=alloc_status)
      allocate(c(n,n),stat=alloc_status)

      !get random matrix a
      do i = 1, n
         do j = 1, n
            a(i, j) = rand(0)
         end do
      end do

      !get random matrix b
      do i = 1, n
         do j = 1, n
            b(i, j) = rand(0)
         end do
      end do

      !initilize matrix c (0 everywhere)
      do i = 1, n
         do j = 1, n
            c(i, j) = 0
         end do
      end do


      call cpu_time ( t1 )

      do i = 1, n
         do j = 1, n
            do k = 1, n
               c(i, j) = c(i, j) + (a(i, k) * b(k, j))
            end do
         end do
      end do

      call cpu_time ( t2 )


      write ( *, * ) 'dimension =', n, ' time needed:', t2 - t1, 'sec'

      deallocate(a,stat=dealloc_status)
      deallocate(b,stat=dealloc_status)
      deallocate(c,stat=dealloc_status)

   end do

   write ( *, * ) 'Enter any key to finish'
   read (*,*) finishProgram

end program MatrMul