*DECK TRIX SUBROUTINE TRIX (IDEGBR, IDEGCR, M, A, B, C, Y, TCOS, D, W) C***BEGIN PROLOGUE TRIX C***SUBSIDIARY C***PURPOSE Subsidiary to GENBUN C***LIBRARY SLATEC C***TYPE SINGLE PRECISION (TRIX-S, CMPTRX-C) C***AUTHOR (UNKNOWN) C***DESCRIPTION C C Subroutine to solve a system of linear equations where the C coefficient matrix is a rational function in the matrix given by C TRIDIAGONAL ( . . . , A(I), B(I), C(I), . . . ). C C***SEE ALSO GENBUN C***ROUTINES CALLED (NONE) C***REVISION HISTORY (YYMMDD) C 801001 DATE WRITTEN C 891214 Prologue converted to Version 4.0 format. (BAB) C 900402 Added TYPE section. (WRB) C***END PROLOGUE TRIX C DIMENSION A(*) ,B(*) ,C(*) ,Y(*) , 1 TCOS(*) ,D(*) ,W(*) INTEGER KB, KC C***FIRST EXECUTABLE STATEMENT TRIX MM1 = M-1 KB = IDEGBR+1 KC = IDEGCR+1 L = (IDEGBR+1)/(IDEGCR+1) LINT = 1 DO 108 K=1,IDEGBR X = TCOS(K) IF (K .NE. L) GO TO 102 I = IDEGBR+LINT XX = X-TCOS(I) DO 101 I=1,M W(I) = Y(I) Y(I) = XX*Y(I) 101 CONTINUE 102 CONTINUE Z = 1./(B(1)-X) D(1) = C(1)*Z Y(1) = Y(1)*Z DO 103 I=2,MM1 Z = 1./(B(I)-X-A(I)*D(I-1)) D(I) = C(I)*Z Y(I) = (Y(I)-A(I)*Y(I-1))*Z 103 CONTINUE Z = B(M)-X-A(M)*D(MM1) IF (Z .NE. 0.) GO TO 104 Y(M) = 0. GO TO 105 104 Y(M) = (Y(M)-A(M)*Y(MM1))/Z 105 CONTINUE DO 106 IP=1,MM1 I = M-IP Y(I) = Y(I)-D(I)*Y(I+1) 106 CONTINUE IF (K .NE. L) GO TO 108 DO 107 I=1,M Y(I) = Y(I)+W(I) 107 CONTINUE LINT = LINT+1 L = (LINT*KB)/KC 108 CONTINUE RETURN END