share/odepack/fortran/dfnorm.f

   1 *DECK DFNORM
   2       DOUBLE PRECISION FUNCTION DFNORM (N, A, W)
   3 C-----------------------------------------------------------------------
   4 C This function computes the norm of a full N by N matrix,
   5 C stored in the array A, that is consistent with the weighted max-norm
   6 C on vectors, with weights stored in the array W:
   7 C   DFNORM = MAX(i=1,...,N) ( W(i) * Sum(j=1,...,N) ABS(a(i,j))/W(j) )
   8 C-----------------------------------------------------------------------
   9       INTEGER N,   I, J
  10       DOUBLE PRECISION A,   W, AN, SUM
  11       DIMENSION A(N,N), W(N)
  12       AN = 0.0D0
  13       DO 20 I = 1,N
  14         SUM = 0.0D0
  15         DO 10 J = 1,N
  16  10       SUM = SUM + ABS(A(I,J))/W(J)
  17         AN = MAX(AN,SUM*W(I))
  18  20     CONTINUE
  19       DFNORM = AN
  20       RETURN
  21 C----------------------- End of Function DFNORM ------------------------
  22       END