f90: Multiply two matrices to each other. You can choose to feed the matrices to the program through a file or console keyboard. *.exe and *.out are the Windows and Linux executables.

matmul.exe

matmul.f90

PROGRAM mmult

IMPLICIT NONE

! Declarations

INTEGER:: i, j, k, row, cola, colb, error
REAL,DIMENSION(:,:),ALLOCATABLE:: A, B, C
 CHARACTER(1):: h
 CHARACTER(20):: infile, outfile, exiit

! Opening prints

PRINT*,
PRINT*,
PRINT*, 'This program is written by Mohammad A. Nilforooshan.'
PRINT*, 'All rights reserved.'
PRINT*, 'http://sites.google.com/site/mannprofile/'

! Ask for the input way

PRINT*,
PRINT*,
PRINT*, 'How do you want to input the matrices?'
PRINT*,
PRINT*, 'From a file: (press "y")'
PRINT*, '(Max. number of rows and columns = 50)'
PRINT*,
PRINT*, 'From console keyboard: (press any other key)'
PRINT*, '(Max. number of rows and columns = 10)'
READ*, h

IF (h/='y') THEN
GO TO 113
END IF

! Ask for the name of the input file, open and check it

PRINT*,
PRINT*,
PRINT*, 'Insert the name of the input file.'
PRINT*, 'In the file, start matrix B from the first line after matrix A.'
READ*, infile
OPEN(UNIT=10, FILE=infile, STATUS='OLD', IOSTAT=error)

IF (error/=0) THEN
    PRINT*,
    PRINT*,
    PRINT*, 'Error reading file.'
    STOP
END IF

! Ask the sizes of the matrices in the file

PRINT*,
PRINT*,
PRINT*, 'Insert the number of rows for matrix A.'
READ*, row

IF (row>50) THEN
    STOP
END IF

PRINT*,
PRINT*,
PRINT*, 'Insert the number of columns for matrix A.'
READ*, cola

IF (cola>50) THEN
    STOP
END IF

PRINT*,
PRINT*,
PRINT*, 'Insert the number of columns for matrix B.'
READ*, colb

IF (colb>50) THEN
    STOP
END IF

ALLOCATE(A(row,cola))
ALLOCATE(B(cola,colb))

! Read the matrices from the file

READ(10,*) ((A(i,j),j=1,cola),i=1,row)
READ(10,*) ((B(i,j),j=1,colb),i=1,cola)

! Create the output

ALLOCATE(C(row,colb))
 C=MATMUL(A,B)

! Ask for the name of the output file

PRINT*,
PRINT*,
PRINT*, 'Insert the name of the output file.'
READ*, outfile

! Write in the output file

OPEN(UNIT=11, FILE=outfile, STATUS='UNKNOWN')
DO i=1,row
    WRITE(11,'(50F10.3)') (C(i,j), j=1,colb)
END DO

GO TO 187

! Ask the sizes of the matrices

113 PRINT*,
PRINT*,
PRINT*, 'Insert the number of rows for matrix A.'
READ*, row

IF (row>10) THEN
    STOP
END IF

PRINT*,
PRINT*,
PRINT*, 'Insert the number of columns for matrix A.'
READ*, cola

IF (cola>10) THEN
    STOP
END IF

PRINT*,
PRINT*,
PRINT*, 'Insert the number of columns for matrix B.'
READ*, colb

IF (colb>10) THEN
    STOP
END IF

ALLOCATE(A(row,cola))
ALLOCATE(B(cola,colb))

! Read the matrices from console keyboard

PRINT*,
PRINT*,
PRINT*, 'Insert matrix A (column-wise).'
PRINT*,
PRINT*,

DO j=1,cola
    PRINT*, 'Insert column',j
    DO i=1,row
        READ*, A(i,j)
    END DO
END DO

PRINT*,
PRINT*,
PRINT*, 'Insert matrix B (column-wise).'
PRINT*,
PRINT*,

DO j=1,colb
    PRINT*, 'Insert column',j
    DO i=1,cola
        READ*, B(i,j)
    END DO
END DO

! Create the output

ALLOCATE(C(row,colb))
 C=MATMUL(A,B)

! Print the results on the screen

PRINT*,
PRINT*,
PRINT*, 'A x B ='
DO i=1,row
    WRITE(*,'(10F11.3)') (C(i,j), j=1,colb)
END DO

! Finished

187 PRINT*,
PRINT*,
PRINT*, 'Press any key to exit.'
READ*, exiit

IF (exiit=='a') THEN
GO TO 196
END IF

196 END PROGRAM mmult

matmul.out