program matrix
	    implicit none
	    integer, parameter :: rows1 = 500, cols1 = 500
	    integer, parameter :: rows2 = 500, cols2 = 500
            integer, parameter :: maxnum = 10
	    integer m(rows1, cols1)
	    integer n(rows2, cols2)
	    integer prod(rows1, cols2)
	    integer prod2(rows1, cols2)
            real, dimension(5) :: randomarray   ! used for timing
            integer :: same
            character(20) :: filename1, filename2, filename3
    
	    integer time_array_0(8), time_array_1(8)
            real start_time, finish_time
            call random_seed()
		
            filename1='matrix500.txt'
            filename2='matrix500B.txt'

            write(*,*) 'Reading first matrix from file...'
	    call matrixFromFile(m, rows1, cols1, filename1, 10)

            write(*,*) 'Reading second matrix from file...'
	    call matrixFromFile(n, rows2, cols2, filename2, 20)

	    write(*,*) 'Starting matrix multiplication...'
            call date_and_time(values=time_array_0)
            start_time = time_array_0 (5) * 3600 + time_array_0 (6) * 60 &
                       + time_array_0 (7) + 0.001 * time_array_0 (8)
            write (6, '(8x, 1a, 1f16.6)') 'begin (date_and_time):  ', &
                             start_time

            call matMult(m,n,prod, rows1, cols1, rows2, cols2)
            call date_and_time(values=time_array_1)
            finish_time = time_array_1 (5) * 3600 + time_array_1 (6) * 60 &
                       + time_array_1 (7) + 0.001 * time_array_1 (8)
                       
            write(*,*) 'End matrix multiplication'
            write (6, '(8x, 1a, 1f16.6)') 'end (date_and_time):    ', &
                 finish_time
            write(*,*) 'Total time=', finish_time - start_time     

            filename3 = 'prod500.txt'
            write(*,*) 'Reading product matrix solution from file...'
            call matrixFromFile(prod2, rows1,cols1, filename3, 30)

            call checkMatrices(prod,prod2, rows1, cols1, same)

            write(*,*) 'Same =', same
            if (same .eq. 1) then
                write(*,*) 'Your answer agrees with mine'
            else 
                write(*,*) 'Your answer is not the same as mine'
            end if
            
          contains 
	     subroutine matMult(m, n, prod, rows1, cols1, rows2, cols2)
	        implicit none
                integer, intent(in) :: rows1, cols1, rows2, cols2
		integer, dimension(rows1,cols1), intent(in) :: m
		integer, dimension(rows2,cols2), intent(in) :: n
		integer, dimension(rows1,cols2), intent(out) :: prod
		integer i, j, k

 !             Insert your code for matrix multiplication here




 

            end subroutine
	    
	     subroutine checkMatrices(m, n, rows, cols, same)
	        implicit none
                integer, intent(in) :: rows, cols
		integer, dimension(rows,cols), intent(in) :: m,n
		integer, intent(out) :: same
		integer i, j
		
                same = 1
		do i=1, rows
		    do j = 1, cols
		        if (m(i,j) /= n(i,j) ) then
                            same=0
                            write(*,*) 'Not the same at ', i, j
			end if
		    end do
		end do
	     end subroutine

             subroutine matrixToFile(rows, cols, filename, filenum)
	        implicit none
                integer, intent(in) :: rows, cols
		integer, dimension(rows,cols) :: m
                character(20), intent(in) :: filename
                integer, intent(in) :: filenum
		integer i, j
		
                open(filenum,file=filename)
		do i=1,rows
		    do j = 1, cols
		        call random_number(randomarray)
			m(i,j) = int(randomarray(1)*maxnum)
                        write(filenum,*) m(i,j)
		    end do
		end do
                close(filenum)
	     end subroutine

             subroutine matrixFromFile(m, rows, cols, filename, filenum)
	        implicit none
                integer, intent(in) :: rows, cols
		integer, dimension(rows,cols),intent(out) :: m
                character(20), intent(in) :: filename
                integer, intent(in) :: filenum
		integer i, j
		
                open(filenum,file=filename)
		do i=1,rows
		    do j = 1, cols
		        read(filenum,*) m(i,j)
		    end do
		end do
                close(filenum)
	     end subroutine

             subroutine matrixWriteToFile(m, rows, cols, filename, filenum)
	        implicit none
                integer, intent(in) :: rows, cols
		integer, dimension(rows,cols),intent(in) :: m
                character(20), intent(in) :: filename
                integer, intent(in) :: filenum
		integer i, j
		
                open(filenum,file=filename)
		do i=1,rows
		    do j = 1, cols
		        write(filenum,*) m(i,j)
		    end do
		end do
                close(filenum)
	     end subroutine
           
	     subroutine printMatrix(m, rows, cols)
	        implicit none
                integer, intent(in) :: rows, cols
		integer, dimension(rows,cols), intent(in) :: m
		integer i, j	
		
		do i=1,rows
		    write(*,*) (m(i,j), j = 1,cols)		
		end do
	     end subroutine	
	     
	
	END PROGRAM