 
      SUBROUTINE XDRED(X,IX)
C***BEGIN PROLOGUE  XDRED
C***DATE WRITTEN   820712   (YYMMDD)
C***REVISION DATE  831027   (YYMMDD)
C***CATEGORY NO.  A3d
C***KEYWORDS  EXTENDED-RANGE DOUBLE-PRECISION ARITHMETIC
C***AUTHOR  LOZIER, DANIEL W. (NATIONAL BUREAU OF STANDARDS)
C           SMITH, JOHN M. (NBS AND GEORGE MASON UNIVERSITY)
C***PURPOSE  TO PROVIDE DOUBLE-PRECISION FLOATING-POINT ARITHMETIC
C            WITH AN EXTENDED EXPONENT RANGE
C***DESCRIPTION
C     DOUBLE PRECISION X
C     INTEGER IX
C
C                  IF
C                  RADIX**(-2L) .LE. (DABS(X),IX) .LE. RADIX**(2L)
C                  THEN XDRED TRANSFORMS (X,IX) SO THAT IX=0.
C                  IF (X,IX) IS OUTSIDE THE ABOVE RANGE,
C                  THEN XDRED TAKES NO ACTION.
C                  THIS SUBROUTINE IS USEFUL IF THE
C                  RESULTS OF EXTENDED-RANGE CALCULATIONS
C                  ARE TO BE USED IN SUBSEQUENT ORDINARY
C                  DOUBLE-PRECISION CALCULATIONS.
C
C***REFERENCES  (PROGRAM LISTING FOR XDSET)
C***ROUTINES CALLED  (NONE)
C***COMMON BLOCKS    XDBLK2
C***END PROLOGUE  XDRED
 
 
