!*********************************************************************************************************************************** ! ! M 3 3 D E T _ M A I N ! ! Program: M33DET_MAIN ! ! Programmer: David G. Simpson ! NASA Goddard Space Flight Center ! Greenbelt, Maryland 20771 ! ! Date: July 22, 2005 ! ! Language: Fortran-90 ! ! Version: 1.00a ! ! Description: This program is a short "driver" to call function M33DET, which computes the determinant a 3x3 matrix. ! ! Files: Source files: ! ! m33det.f90 Main program ! !*********************************************************************************************************************************** PROGRAM M33DET_MAIN IMPLICIT NONE INTEGER :: I, J DOUBLE PRECISION, DIMENSION(3,3) :: MAT DOUBLE PRECISION :: DET DOUBLE PRECISION :: M33DET !----------------------------------------------------------------------------------------------------------------------------------- ! ! Get user input. ! WRITE (UNIT=*, FMT='(/A/)') ' Enter matrix:' DO I = 1, 3 DO J = 1, 3 WRITE (UNIT=*, FMT='(A,I1,1H,,I1,A)', ADVANCE='NO') ' A(', I, J, ') = ' READ (UNIT=*, FMT=*) MAT(I,J) END DO END DO ! ! Compute the determinant of the input matrix. ! DET = M33DET (MAT) ! ! Print the result. ! WRITE (UNIT=*, FMT='(/A,ES25.15)') ' Det = ', DET STOP END PROGRAM M33DET_MAIN !*********************************************************************************************************************************** ! M33DET - Compute the determinant of a 3x3 matrix. !*********************************************************************************************************************************** FUNCTION M33DET (A) RESULT (DET) IMPLICIT NONE DOUBLE PRECISION, DIMENSION(3,3), INTENT(IN) :: A DOUBLE PRECISION :: DET DET = A(1,1)*A(2,2)*A(3,3) & - A(1,1)*A(2,3)*A(3,2) & - A(1,2)*A(2,1)*A(3,3) & + A(1,2)*A(2,3)*A(3,1) & + A(1,3)*A(2,1)*A(3,2) & - A(1,3)*A(2,2)*A(3,1) RETURN END FUNCTION M33DET