DDSTP(3)

SYNOPSIS
SUBROUTINE DDSTP (EPS, F, FA, HMAX, IMPL, IERROR, JACOBN, MATDIM, 8 MAXORD, MINT, MITER, ML, MU, N, NDE, YWT, UROUND, USERS, AVGH, 8 AVGORD, H, HUSED, JTASK, MNTOLD, MTROLD, NFE, NJE, NQUSED, 8 NSTEP, T, Y, YH, A, CONVRG, DFDY, EL, FAC, HOLD, IPVT, JSTATE, 8 JSTEPL, NQ, NWAIT, RC, RMAX, SAVE1, SAVE2, TQ, TREND, ISWFLG, 8 MTRSV, MXRDSV)

NAME
ddstp - DDSTP performs one step of the integration of an initial value problem for a system of ordinary differential equations.

LIBRARY
SLATEC (SDRIVE)

TYPE
DOUBLE PRECISION (SDSTP-S, DDSTP-D, CDSTP-C)

AUTHOR
Kahaner, D. K., (NIST) National Institute of Standards and Technology Gaithersburg, MD 20899 Sutherland, C. D., (LANL) Mail Stop D466 Los Alamos National Laboratory Los Alamos, NM 87545

DESCRIPTION
Communication with DDSTP is done with the following variables: YH An N by MAXORD+1 array containing the dependent variables and their scaled derivatives. MAXORD, the maximum order used, is currently 12 for the Adams methods and 5 for the Gear methods. YH(I,J+1) contains the J-th derivative of Y(I), scaled by H**J/factorial(J). Only Y(I), 1 .LE. I .LE. N, need be set by the calling program on the first entry. The YH array should not be altered by the calling program. When referencing YH as a 2-dimensional array, use a column length of N, as this is the value used in DDSTP. DFDY A block of locations used for partial derivatives if MITER is not 0. If MITER is 1 or 2 its length must be at least N*N. If MITER is 4 or 5 its length must be at least (2*ML+MU+1)*N. YWT An array of N locations used in convergence and error tests SAVE1 SAVE2 Arrays of length N used for temporary storage. IPVT An integer array of length N used by the linear system solvers for the storage of row interchange information. A A block of locations used to store the matrix A, when using the implicit method. If IMPL is 1, A is a MATDIM by N array. If MITER is 1 or 2 MATDIM is N, and if MITER is 4 or 5 MATDIM is 2*ML+MU+1. If IMPL is 2 its length is N. If IMPL is 3, A is a MATDIM by NDE array. JTASK An integer used on input. It has the following values and meanings: the subroutine to initialize itself. Assumes the last step was successful and user has not changed any parameters. MINT and/or MITER. JSTATE A completion code with the following meanings: 1 The step was successful. 2 A solution could not be obtained with H .NE. 0. 3 A solution was not obtained in MXTRY attempts. 4 For IMPL .NE. 0, the matrix A is singular. On a return with JSTATE .GT. 1, the values of T and the YH array are as of the beginning of the last step, and H is the last step size attempted.

ROUTINES CALLED
DDCOR, DDCST, DDNTL, DDPSC, DDPST, DDSCL, DNRM2

REVISION HISTORY (YYMMDD)
790601 DATE WRITTEN
900329 Initial submission to SLATEC.