*DECK DDZRO SUBROUTINE DDZRO (AE, F, H, N, NQ, IROOT, RE, T, YH, UROUND, B, C, 8 FB, FC, Y) C***BEGIN PROLOGUE DDZRO C***SUBSIDIARY C***PURPOSE DDZRO searches for a zero of a function F(N, T, Y, IROOT) C between the given values B and C until the width of the C interval (B, C) has collapsed to within a tolerance C specified by the stopping criterion, C ABS(B - C) .LE. 2.*(RW*ABS(B) + AE). C***LIBRARY SLATEC (SDRIVE) C***TYPE DOUBLE PRECISION (SDZRO-S, DDZRO-D, CDZRO-C) C***AUTHOR Kahaner, D. K., (NIST) C National Institute of Standards and Technology C Gaithersburg, MD 20899 C Sutherland, C. D., (LANL) C Mail Stop D466 C Los Alamos National Laboratory C Los Alamos, NM 87545 C***DESCRIPTION C C This is a special purpose version of ZEROIN, modified for use with C the DDRIV package. C C Sandia Mathematical Program Library C Mathematical Computing Services Division 5422 C Sandia Laboratories C P. O. Box 5800 C Albuquerque, New Mexico 87115 C Control Data 6600 Version 4.5, 1 November 1971 C C PARAMETERS C F - Name of the external function, which returns a C double precision result. This name must be in an C EXTERNAL statement in the calling program. C B - One end of the interval (B, C). The value returned for C B usually is the better approximation to a zero of F. C C - The other end of the interval (B, C). C RE - Relative error used for RW in the stopping criterion. C If the requested RE is less than machine precision, C then RW is set to approximately machine precision. C AE - Absolute error used in the stopping criterion. If the C given interval (B, C) contains the origin, then a C nonzero value should be chosen for AE. C C***REFERENCES L. F. Shampine and H. A. Watts, ZEROIN, a root-solving C routine, SC-TM-70-631, Sept 1970. C T. J. Dekker, Finding a zero by means of successive C linear interpolation, Constructive Aspects of the C Fundamental Theorem of Algebra, edited by B. Dejon C and P. Henrici, 1969. C***ROUTINES CALLED DDNTP C***REVISION HISTORY (YYMMDD) C 790601 DATE WRITTEN C 900329 Initial submission to SLATEC. C***END PROLOGUE DDZRO