*DECK DEFE4 SUBROUTINE DEFE4 (COFX, IDMN, USOL, GRHS) C***BEGIN PROLOGUE DEFE4 C***SUBSIDIARY C***PURPOSE Subsidiary to SEPX4 C***LIBRARY SLATEC C***TYPE SINGLE PRECISION (DEFE4-S) C***AUTHOR (UNKNOWN) C***DESCRIPTION C C This subroutine first approximates the truncation error given by C TRUN1(X,Y)=DLX**2*TX+DLY**2*TY where C TX=AFUN(X)*UXXXX/12.0+BFUN(X)*UXXX/6.0 on the interior and C at the boundaries if periodic (here UXXX,UXXXX are the third C and fourth partial derivatives of U with respect to X). C TX is of the form AFUN(X)/3.0*(UXXXX/4.0+UXXX/DLX) C at X=A or X=B if the boundary condition there is mixed. C TX=0.0 along specified boundaries. TY has symmetric form C in Y with X,AFUN(X),BFUN(X) replaced by Y,DFUN(Y),EFUN(Y). C The second order solution in USOL is used to approximate C (via second order finite differencing) the truncation error C and the result is added to the right hand side in GRHS C and then transferred to USOL to be used as a new right C hand side when calling BLKTRI for a fourth order solution. C C***SEE ALSO SEPX4 C***ROUTINES CALLED DX4, DY4 C***COMMON BLOCKS SPL4 C***REVISION HISTORY (YYMMDD) C 801001 DATE WRITTEN C 890531 Changed all specific intrinsics to generic. (WRB) C 891214 Prologue converted to Version 4.0 format. (BAB) C 900402 Added TYPE section. (WRB) C***END PROLOGUE DEFE4