ddwnrm.f

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C Work performed under the auspices of the U.S. Department of Energy
C by Lawrence Livermore National Laboratory under contract number
C W-7405-Eng-48.
C
      DOUBLE PRECISION FUNCTION ddwnrm(NEQ,V,RWT,RPAR,IPAR)
C
C***BEGIN PROLOGUE  DDWNRM
C***ROUTINES CALLED  (NONE)
C***DATE WRITTEN   890101   (YYMMDD)
C***REVISION DATE  900926   (YYMMDD)
C***END PROLOGUE  DDWNRM
C-----------------------------------------------------------------------
C     This function routine computes the weighted
C     root-mean-square norm of the vector of length
C     NEQ contained in the array V, with reciprocal weights
C     contained in the array RWT of length NEQ.
C        DDWNRM=SQRT((1/NEQ)*SUM(V(I)*RWT(I))**2)
C-----------------------------------------------------------------------
C
      IMPLICIT DOUBLE PRECISION(a-h,o-z)
      dimension v(*),rwt(*)
      dimension rpar(*),ipar(*)
      ddwnrm = 0.0d0
      vmax = 0.0d0
      DO 10 i = 1,neq
        IF(abs(v(i)*rwt(i)) .GT. vmax) vmax = abs(v(i)*rwt(i))
10    CONTINUE
      IF(vmax .LE. 0.0d0) go to 30
      sum = 0.0d0
      DO 20 i = 1,neq
20      sum = sum + ((v(i)*rwt(i))/vmax)**2
      ddwnrm = vmax*sqrt(sum/neq)
30    CONTINUE
      RETURN
C
C------END OF FUNCTION DDWNRM-------------------------------------------
      END