share/odepack/fortran/dvnorm.f

   1 *DECK DVNORM
   2       DOUBLE PRECISION FUNCTION DVNORM (N, V, W)
   3 C***BEGIN PROLOGUE  DVNORM
   4 C***SUBSIDIARY
   5 C***PURPOSE  Weighted root-mean-square vector norm.
   6 C***TYPE      DOUBLE PRECISION (SVNORM-S, DVNORM-D)
   7 C***AUTHOR  Hindmarsh, Alan C., (LLNL)
   8 C***DESCRIPTION
   9 C
  10 C  This function routine computes the weighted root-mean-square norm
  11 C  of the vector of length N contained in the array V, with weights
  12 C  contained in the array W of length N:
  13 C    DVNORM = SQRT( (1/N) * SUM( V(i)*W(i) )**2 )
  14 C
  15 C***SEE ALSO  DLSODE
  16 C***ROUTINES CALLED  (NONE)
  17 C***REVISION HISTORY  (YYMMDD)
  18 C   791129  DATE WRITTEN
  19 C   890501  Modified prologue to SLATEC/LDOC format.  (FNF)
  20 C   890503  Minor cosmetic changes.  (FNF)
  21 C   930809  Renamed to allow single/double precision versions. (ACH)
  22 C***END PROLOGUE  DVNORM
  23 C**End
  24       INTEGER N,   I
  25       DOUBLE PRECISION V, W,   SUM
  26       DIMENSION V(N), W(N)
  27 C
  28 C***FIRST EXECUTABLE STATEMENT  DVNORM
  29       SUM = 0.0D0
  30       DO 10 I = 1,N
  31  10     SUM = SUM + (V(I)*W(I))**2
  32       DVNORM = SQRT(SUM/N)
  33       RETURN
  34 C----------------------- END OF FUNCTION DVNORM ------------------------
  35       END