Sources Esope | Cast3M

inver3
C INVER3    SOURCE    CHAT      05/01/13    00:42:42     5004
C INVER3     SOURCE    INSL       24/10/96
      SUBROUTINE INVER3(A,B)
C
      IMPLICIT INTEGER(I-N)
      IMPLICIT REAL*8 (A-H,O-Z)
      DIMENSION A(3,3),B(3,3)
C
C            INVERSION MANUELLE D UNE MATRICE 3X3
C                (A)**-1=(B)
C
      PREC=1.D-8
C            CALCUL DU DETERMINANT
      DELTA=A(1,1)*A(2,2)*A(3,3)+A(1,2)*A(2,3)*A(3,1)+
     A      A(2,1)*A(3,2)*A(1,3)-A(3,1)*A(2,2)*A(1,3)-
     B      A(2,1)*A(1,2)*A(3,3)-A(3,2)*A(2,3)*A(1,1)
      IF(DELTA .GT. -PREC  .AND.  DELTA .LT. PREC) THEN
         WRITE(*,*) ' ** ERREUR ** DETERMINANT NUL',DELTA
         STOP
      ELSE
      B(1,1)= (A(2,2)*A(3,3)-A(3,2)*A(2,3))/DELTA
      B(2,1)=-(A(1,2)*A(3,3)-A(3,2)*A(1,3))/DELTA
      B(3,1)= (A(1,2)*A(2,3)-A(2,2)*A(1,3))/DELTA
      B(1,2)=-(A(2,1)*A(3,3)-A(3,1)*A(2,3))/DELTA
      B(2,2)= (A(1,1)*A(3,3)-A(3,1)*A(1,3))/DELTA
      B(3,2)=-(A(1,1)*A(2,3)-A(2,1)*A(1,3))/DELTA
      B(1,3)= (A(2,1)*A(3,2)-A(3,1)*A(2,2))/DELTA
      B(2,3)=-(A(1,1)*A(3,2)-A(3,1)*A(1,2))/DELTA
      B(3,3)= (A(1,1)*A(2,2)-A(2,1)*A(1,2))/DELTA
C          TRANSPOSONS
      T=B(1,2)
      B(1,2)=B(2,1)
      B(2,1)=T
      T=B(1,3)
      B(1,3)=B(3,1)
      B(3,1)=T
      T=B(2,3)
      B(2,3)=B(3,2)
      B(3,2)=T
      ENDIF
      RETURN
      END