SUBROUTINE TRID (MR,A,B,C,Y,D) DIMENSION A(1) ,B(1) ,C(1) ,Y(1) , 1 D(1) M = MR MM1 = M-1 Z = 1./B(1) D(1) = C(1)*Z Y(1) = Y(1)*Z DO 101 I=2,MM1 Z = 1./(B(I)-A(I)*D(I-1)) D(I) = C(I)*Z Y(I) = (Y(I)-A(I)*Y(I-1))*Z 101 CONTINUE Z = B(M)-A(M)*D(MM1) IF (Z .NE. 0.) GO TO 102 Y(M) = 0. GO TO 103 102 Y(M) = (Y(M)-A(M)*Y(MM1))/Z 103 CONTINUE DO 104 IP=1,MM1 I = M-IP Y(I) = Y(I)-D(I)*Y(I+1) 104 CONTINUE RETURN END