!===============================================================================
! Copyright 2009-2018 Intel Corporation.
!
! This software and the related documents are Intel copyrighted  materials,  and
! your use of  them is  governed by the  express license  under which  they were
! provided to you (License).  Unless the License provides otherwise, you may not
! use, modify, copy, publish, distribute,  disclose or transmit this software or
! the related documents without Intel's prior written permission.
!
! This software and the related documents  are provided as  is,  with no express
! or implied  warranties,  other  than those  that are  expressly stated  in the
! License.
!===============================================================================

!  Content: DJACOBI RCI Example
!
!  The program computes the Jacobi matrix of the function on the basis of RCI
!  using the central difference.
!*******************************************************************************

      PROGRAM JACOBI_MATRIX
        IMPLICIT NONE
C**
        INCLUDE 'mkl_rci.fi'
C**
        EXTERNAL EXTENDED_POWELL
C**
C** N - Number of function variables
C** M - Dimension of function value
        INTEGER N, M, I
        PARAMETER (N = 4)
        PARAMETER (M = 4)
C**
C** Jacobi matrix
        REAL*4 A (M,N)
C** Solution vector. contains values x for f(x)
C** Temporary arrays f1 & f2 which contains f1 = f(x+eps) | f2 = f(x-eps)
        REAL*4 F1(M), F2(M), X(N)
C** Precisions for jacobi_matrix calculation
        REAL*4 EPS
C**
C** Jacobi-matrix solver handle
        INTEGER*8 HANDLE
C** Controls of rci cycle
        INTEGER SUCCESSFUL, RCI_REQUEST
        INTEGER RESULT
C**
C** Set the x values
C** X   = 10.D0
        DO I = 1, N
            X(I) = 10.0D0
        END DO
C**
        EPS = 1.D-6
        PRINT *, 'START TESTING ...'
C** Initialize solver (allocate memory, set initial values)
        RESULT = SJACOBI_INIT (HANDLE, N, M, X, A, EPS)
        IF ( RESULT .NE. TR_SUCCESS) THEN
C** If function does not complete successfully then print error message
            PRINT *, '#FAIL: ERROR IN DJACOBI_INIT'
            CALL MKL_FREE_BUFFERS
            STOP 1
        END IF
C** Set initial rci cycle variables
        RCI_REQUEST = 0
        SUCCESSFUL  = 0
C** Rci cycle
        DO WHILE (SUCCESSFUL .EQ. 0)
C** Call solver
            IF (SJACOBI_SOLVE (HANDLE, F1, F2, RCI_REQUEST) .NE.
     &  TR_SUCCESS) THEN
C** If function does not complete successfully then print error message
                PRINT *, '#FAIL: ERROR IN DJACOBI_SOLVE'
                CALL MKL_FREE_BUFFERS
                STOP 1
            END IF
            IF (RCI_REQUEST .EQ. 1) THEN
C** Calculate the function value f1 = f(x+eps)
                CALL EXTENDED_POWELL (M, N, X, F1)
            ELSE IF (RCI_REQUEST .EQ. 2) THEN
C** Calculate the function value f2 = f(x-eps)
                CALL EXTENDED_POWELL (M, N, X, F2)
            ELSE IF (RCI_REQUEST.EQ.0) THEN
C** Exit rci cycle
                SUCCESSFUL = 1
            END IF
        END DO
C** Free handle memory
        IF (SJACOBI_DELETE (HANDLE).NE.TR_SUCCESS) THEN
C** If function does not complete successfully then print error message
            PRINT *, '#FAIL: ERROR IN DJACOBI_DELETE'
            CALL MKL_FREE_BUFFERS
            STOP 1
        END IF
        PRINT *, '#PASS'
      END PROGRAM JACOBI_MATRIX
C**
C** Routine for extended Powell function calculation
C** M in: dimension of function value
C** N in: number of function variables
C** X in: vector for function calculation
C** F out: function value f(x)
C**
      SUBROUTINE EXTENDED_POWELL (M, N, X, F)
        IMPLICIT NONE
        INTEGER M, N
        REAL*4 X (*), F (*)
        INTEGER I
        DO I = 1, N/4
            F (4*I-3) = X(4*I - 3) + 10.D0 * X(4*I - 2)
            F (4*I-2) = DSQRT(5.D0) * (X(4*I-1) - X(4*I))
            F (4*I-1) = ( X(4*I-2) - 2.D0*X(4*I-1) )**2
            F (4*I)   = DSQRT(10.D0) * (X(4*I-3) - X(4*I))**2
        END DO
      END SUBROUTINE EXTENDED_POWELL