SUBROUTINE LUDCMP(A,N,NP,INDX,D) PARAMETER (NMAX=100,TINY=1.0E-20) DIMENSION A(NP,NP),INDX(N),VV(NMAX) D=1. DO 12 I=1,N AAMAX=0. DO 11 J=1,N IF (ABS(A(I,J)).GT.AAMAX) AAMAX=ABS(A(I,J)) 11 CONTINUE IF (AAMAX.EQ.0.) PAUSE 'Singular matrix.' VV(I)=1./AAMAX 12 CONTINUE DO 19 J=1,N IF (J.GT.1) THEN DO 14 I=1,J-1 SUM=A(I,J) IF (I.GT.1)THEN DO 13 K=1,I-1 SUM=SUM-A(I,K)*A(K,J) 13 CONTINUE A(I,J)=SUM ENDIF 14 CONTINUE ENDIF AAMAX=0. DO 16 I=J,N SUM=A(I,J) IF (J.GT.1)THEN DO 15 K=1,J-1 SUM=SUM-A(I,K)*A(K,J) 15 CONTINUE A(I,J)=SUM ENDIF DUM=VV(I)*ABS(SUM) IF (DUM.GE.AAMAX) THEN IMAX=I AAMAX=DUM ENDIF 16 CONTINUE IF (J.NE.IMAX)THEN DO 17 K=1,N DUM=A(IMAX,K) A(IMAX,K)=A(J,K) A(J,K)=DUM 17 CONTINUE D=-D VV(IMAX)=VV(J) ENDIF INDX(J)=IMAX IF(J.NE.N)THEN IF(A(J,J).EQ.0.)A(J,J)=TINY DUM=1./A(J,J) DO 18 I=J+1,N A(I,J)=A(I,J)*DUM 18 CONTINUE ENDIF 19 CONTINUE IF(A(N,N).EQ.0.)A(N,N)=TINY RETURN END