00001 SUBROUTINE DDATRP (X, XOUT, YOUT, YPOUT, NEQ, KOLD, PHI, PSI) 00002 C***BEGIN PROLOGUE DDATRP 00003 C***SUBSIDIARY 00004 C***PURPOSE Interpolation routine for DDASSL. 00005 C***LIBRARY SLATEC (DASSL) 00006 C***TYPE DOUBLE PRECISION (SDATRP-S, DDATRP-D) 00007 C***AUTHOR PETZOLD, LINDA R., (LLNL) 00008 C***DESCRIPTION 00009 C----------------------------------------------------------------------- 00010 C THE METHODS IN SUBROUTINE DDASTP USE POLYNOMIALS 00011 C TO APPROXIMATE THE SOLUTION. DDATRP APPROXIMATES THE 00012 C SOLUTION AND ITS DERIVATIVE AT TIME XOUT BY EVALUATING 00013 C ONE OF THESE POLYNOMIALS,AND ITS DERIVATIVE,THERE. 00014 C INFORMATION DEFINING THIS POLYNOMIAL IS PASSED FROM 00015 C DDASTP, SO DDATRP CANNOT BE USED ALONE. 00016 C 00017 C THE PARAMETERS ARE: 00018 C X THE CURRENT TIME IN THE INTEGRATION. 00019 C XOUT THE TIME AT WHICH THE SOLUTION IS DESIRED 00020 C YOUT THE INTERPOLATED APPROXIMATION TO Y AT XOUT 00021 C (THIS IS OUTPUT) 00022 C YPOUT THE INTERPOLATED APPROXIMATION TO YPRIME AT XOUT 00023 C (THIS IS OUTPUT) 00024 C NEQ NUMBER OF EQUATIONS 00025 C KOLD ORDER USED ON LAST SUCCESSFUL STEP 00026 C PHI ARRAY OF SCALED DIVIDED DIFFERENCES OF Y 00027 C PSI ARRAY OF PAST STEPSIZE HISTORY 00028 C----------------------------------------------------------------------- 00029 C***ROUTINES CALLED (NONE) 00030 C***REVISION HISTORY (YYMMDD) 00031 C 830315 DATE WRITTEN 00032 C 901009 Finished conversion to SLATEC 4.0 format (F.N.Fritsch) 00033 C 901019 Merged changes made by C. Ulrich with SLATEC 4.0 format. 00034 C 901026 Added explicit declarations for all variables and minor 00035 C cosmetic changes to prologue. (FNF) 00036 C***END PROLOGUE DDATRP 00037 C 00038 INTEGER NEQ, KOLD 00039 DOUBLE PRECISION X, XOUT, YOUT(*), YPOUT(*), PHI(NEQ,*), PSI(*) 00040 C 00041 INTEGER I, J, KOLDP1 00042 DOUBLE PRECISION C, D, GAMMA, TEMP1 00043 C 00044 C***FIRST EXECUTABLE STATEMENT DDATRP 00045 KOLDP1=KOLD+1 00046 TEMP1=XOUT-X 00047 DO 10 I=1,NEQ 00048 YOUT(I)=PHI(I,1) 00049 10 YPOUT(I)=0.0D0 00050 C=1.0D0 00051 D=0.0D0 00052 GAMMA=TEMP1/PSI(1) 00053 DO 30 J=2,KOLDP1 00054 D=D*GAMMA+C/PSI(J-1) 00055 C=C*GAMMA 00056 GAMMA=(TEMP1+PSI(J-1))/PSI(J) 00057 DO 20 I=1,NEQ 00058 YOUT(I)=YOUT(I)+C*PHI(I,J) 00059 20 YPOUT(I)=YPOUT(I)+D*PHI(I,J) 00060 30 CONTINUE 00061 RETURN 00062 C 00063 C------END OF SUBROUTINE DDATRP------ 00064 END
1.7.1
