relibc_openlibm/slatec/sdanrm.f

*DECK SDANRM
      REAL FUNCTION SDANRM (NEQ, V, WT, RPAR, IPAR)
C***BEGIN PROLOGUE  SDANRM
C***SUBSIDIARY
C***PURPOSE  Compute vector norm for SDASSL.
C***LIBRARY   SLATEC (DASSL)
C***TYPE      SINGLE PRECISION (SDANRM-S, DDANRM-D)
C***AUTHOR  Petzold, Linda R., (LLNL)
C***DESCRIPTION
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 WEIGHTS
C     CONTAINED IN THE ARRAY WT OF LENGTH NEQ.
C        SDANRM=SQRT((1/NEQ)*SUM(V(I)/WT(I))**2)
C-----------------------------------------------------------------------
C***ROUTINES CALLED  (NONE)
C***REVISION HISTORY  (YYMMDD)
C   830315  DATE WRITTEN
C   901009  Finished conversion to SLATEC 4.0 format (F.N.Fritsch)
C   901019  Merged changes made by C. Ulrich with SLATEC 4.0 format.
C   901026  Added explicit declarations for all variables and minor
C           cosmetic changes to prologue.  (FNF)
C***END PROLOGUE  SDANRM
C
      INTEGER  NEQ, IPAR(*)
      REAL  V(NEQ), WT(NEQ), RPAR(*)
C
      INTEGER  I
      REAL  SUM, VMAX
C
C***FIRST EXECUTABLE STATEMENT  SDANRM
      SDANRM = 0.0E0
      VMAX = 0.0E0
      DO 10 I = 1,NEQ
        IF(ABS(V(I)/WT(I)) .GT. VMAX) VMAX = ABS(V(I)/WT(I))
10      CONTINUE
      IF(VMAX .LE. 0.0E0) GO TO 30
      SUM = 0.0E0
      DO 20 I = 1,NEQ
20      SUM = SUM + ((V(I)/WT(I))/VMAX)**2
      SDANRM = VMAX*SQRT(SUM/NEQ)
30    CONTINUE
      RETURN
C------END OF FUNCTION SDANRM------
      END