Find Determinant

func.f90

    REAL(dp) FUNCTION FindDet(matrix, n)
    IMPLICIT NONE
    REAL(dp), DIMENSION(n,n) :: matrix
    INTEGER, INTENT(IN) :: n
    REAL :: m, temp
    INTEGER :: i, j, k, l
    LOGICAL :: DetExists = .TRUE.
    l = 1
    !Convert to upper triangular form
    DO k = 1, n-1
        IF (matrix(k,k) == 0) THEN
            DetExists = .FALSE.
            DO i = k+1, n
                IF (matrix(i,k) /= 0) THEN
                    DO j = 1, n
                        temp = matrix(i,j)
                        matrix(i,j)= matrix(k,j)
                        matrix(k,j) = temp
                    END DO
                    DetExists = .TRUE.
                    l=-l
                    EXIT
                ENDIF
            END DO
            IF (DetExists .EQV. .FALSE.) THEN
                FindDet = 0
                return
            END IF
        ENDIF
        DO j = k+1, n
            m = matrix(j,k)/matrix(k,k)
            DO i = k+1, n
                matrix(j,i) = matrix(j,i) - m*matrix(k,i)
            END DO
        END DO
    END DO
    
    !Calculate determinant by finding product of diagonal elements
    FindDet = l
    DO i = 1, n
        FindDet = FindDet * matrix(i,i)
    END DO
    
END FUNCTION FindDet