*DECK STOD SUBROUTINE STOD (NEQ, Y, YH, NYH, YH1, EWT, SAVF, ACOR, WM, IWM, + F, JAC, RPAR, IPAR) C***BEGIN PROLOGUE STOD C***SUBSIDIARY C***PURPOSE Subsidiary to DEBDF C***LIBRARY SLATEC C***TYPE SINGLE PRECISION (STOD-S, DSTOD-D) C***AUTHOR Watts, H. A., (SNLA) C***DESCRIPTION C C STOD integrates a system of first order odes over one step in the C integrator package DEBDF. C ---------------------------------------------------------------------- C STOD performs one step of the integration of an initial value C problem for a system of ordinary differential equations. C Note.. STOD is independent of the value of the iteration method C indicator MITER, when this is .NE. 0, and hence is independent C of the type of chord method used, or the Jacobian structure. C Communication with STOD is done with the following variables.. C C Y = An array of length .GE. n used as the Y argument in C all calls to F and JAC. C NEQ = Integer array containing problem size in NEQ(1), and C passed as the NEQ argument in all calls to F and JAC. C YH = An NYH by LMAX array containing the dependent variables C and their approximate scaled derivatives, where C LMAX = MAXORD + 1. YH(I,J+1) contains the approximate C J-th derivative of Y(I), scaled by H**J/Factorial(j) C (J = 0,1,...,NQ). On entry for the first step, the first C two columns of YH must be set from the initial values. C NYH = A constant integer .GE. N, the first dimension of YH. C YH1 = A one-dimensional array occupying the same space as YH. C EWT = An array of N elements with which the estimated local C errors in YH are compared. C SAVF = An array of working storage, of length N. C ACOR = A work array of length N, used for the accumulated C corrections. On a successful return, ACOR(I) contains C the estimated one-step local error in Y(I). C WM,IWM = Real and integer work arrays associated with matrix C operations in chord iteration (MITER .NE. 0). C PJAC = Name of routine to evaluate and preprocess Jacobian matrix C if a chord method is being used. C SLVS = Name of routine to solve linear system in chord iteration. C H = The step size to be attempted on the next step. C H is altered by the error control algorithm during the C problem. H can be either positive or negative, but its C sign must remain constant throughout the problem. C HMIN = The minimum absolute value of the step size H to be used. C HMXI = Inverse of the maximum absolute value of H to be used. C HMXI = 0.0 is allowed and corresponds to an infinite HMAX. C HMIN and HMXI may be changed at any time, but will not C take effect until the next change of H is considered. C TN = The independent variable. TN is updated on each step taken. C JSTART = An integer used for input only, with the following C values and meanings.. C 0 Perform the first step. C .GT.0 Take a new step continuing from the last. C -1 Take the next step with a new value of H, MAXORD, C N, METH, MITER, and/or matrix parameters. C -2 Take the next step with a new value of H, C but with other inputs unchanged. C On return, JSTART is set to 1 to facilitate continuation. C KFLAG = a completion code with the following meanings.. C 0 The step was successful. C -1 The requested error could not be achieved. C -2 Corrector convergence could not be achieved. C A return with KFLAG = -1 or -2 means either C ABS(H) = HMIN or 10 consecutive failures occurred. C On a return with KFLAG negative, the values of TN and C the YH array are as of the beginning of the last C step, and H is the last step size attempted. C MAXORD = The maximum order of integration method to be allowed. C METH/MITER = The method flags. See description in driver. C N = The number of first-order differential equations. C ---------------------------------------------------------------------- C C***SEE ALSO DEBDF C***ROUTINES CALLED CFOD, PJAC, SLVS, VNWRMS C***COMMON BLOCKS DEBDF1 C***REVISION HISTORY (YYMMDD) C 800901 DATE WRITTEN C 890531 Changed all specific intrinsics to generic. (WRB) C 891214 Prologue converted to Version 4.0 format. (BAB) C 900328 Added TYPE section. (WRB) C 910722 Updated AUTHOR section. (ALS) C 920422 Changed DIMENSION statement. (WRB) C***END PROLOGUE STOD