SUBROUTINE DSILUS (N, NELT, IA, JA, A, ISYM, NL, IL, JL, L, DINV,
+ NU, IU, JU, U, NROW, NCOL)
C .. Scalar Arguments ..
INTEGER ISYM, N, NELT, NL, NU
C .. Array Arguments ..
DOUBLE PRECISION A(NELT), DINV(N), L(NL), U(NU)
INTEGER IA(NELT), IL(NL), IU(NU), JA(NELT), JL(NL), JU(NU),
+ NCOL(N), NROW(N)
C .. Local Scalars ..
DOUBLE PRECISION TEMP
INTEGER I, IBGN, ICOL, IEND, INDX, INDX1, INDX2, INDXC1, INDXC2,
+ INDXR1, INDXR2, IROW, ITEMP, J, JBGN, JEND, JTEMP, K, KC,
+ KR
C***FIRST EXECUTABLE STATEMENT DSILUS
C
C Count number of elements in each row of the lower triangle.
C
DO 10 I=1,N
NROW(I) = 0
NCOL(I) = 0
10 CONTINUE
CVD$R NOCONCUR
CVD$R NOVECTOR
DO 30 ICOL = 1, N
JBGN = JA(ICOL)+1
JEND = JA(ICOL+1)-1
IF( JBGN.LE.JEND ) THEN
DO 20 J = JBGN, JEND
IF( IA(J).LT.ICOL ) THEN
NCOL(ICOL) = NCOL(ICOL) + 1
ELSE
NROW(IA(J)) = NROW(IA(J)) + 1
IF( ISYM.NE.0 ) NCOL(IA(J)) = NCOL(IA(J)) + 1
ENDIF
20 CONTINUE
ENDIF
30 CONTINUE
JU(1) = 1
IL(1) = 1
DO 40 ICOL = 1, N
IL(ICOL+1) = IL(ICOL) + NROW(ICOL)
JU(ICOL+1) = JU(ICOL) + NCOL(ICOL)
NROW(ICOL) = IL(ICOL)
NCOL(ICOL) = JU(ICOL)
40 CONTINUE
C
C Copy the matrix A into the L and U structures.
DO 60 ICOL = 1, N
DINV(ICOL) = A(JA(ICOL))
JBGN = JA(ICOL)+1
JEND = JA(ICOL+1)-1
IF( JBGN.LE.JEND ) THEN
DO 50 J = JBGN, JEND
IROW = IA(J)
IF( IROW.LT.ICOL ) THEN
C Part of the upper triangle.
IU(NCOL(ICOL)) = IROW
U(NCOL(ICOL)) = A(J)
NCOL(ICOL) = NCOL(ICOL) + 1
ELSE
C Part of the lower triangle (stored by row).
JL(NROW(IROW)) = ICOL
L(NROW(IROW)) = A(J)
NROW(IROW) = NROW(IROW) + 1
IF( ISYM.NE.0 ) THEN
C Symmetric...Copy lower triangle into upper triangle as well.
IU(NCOL(IROW)) = ICOL
U(NCOL(IROW)) = A(J)
NCOL(IROW) = NCOL(IROW) + 1
ENDIF
ENDIF
50 CONTINUE
ENDIF
60 CONTINUE
C
C Sort the rows of L and the columns of U.
DO 110 K = 2, N
JBGN = JU(K)
JEND = JU(K+1)-1
IF( JBGN.LT.JEND ) THEN
DO 80 J = JBGN, JEND-1
DO 70 I = J+1, JEND
IF( IU(J).GT.IU(I) ) THEN
ITEMP = IU(J)
IU(J) = IU(I)
IU(I) = ITEMP
TEMP = U(J)
U(J) = U(I)
U(I) = TEMP
ENDIF
70 CONTINUE
80 CONTINUE
ENDIF
IBGN = IL(K)
IEND = IL(K+1)-1
IF( IBGN.LT.IEND ) THEN
DO 100 I = IBGN, IEND-1
DO 90 J = I+1, IEND
IF( JL(I).GT.JL(J) ) THEN
JTEMP = JU(I)
JU(I) = JU(J)
JU(J) = JTEMP
TEMP = L(I)
L(I) = L(J)
L(J) = TEMP
ENDIF
90 CONTINUE
100 CONTINUE
ENDIF
110 CONTINUE
C
C Perform the incomplete LDU decomposition.
DO 300 I=2,N
C
C I-th row of L
INDX1 = IL(I)
INDX2 = IL(I+1) - 1
IF(INDX1 .GT. INDX2) GO TO 200
DO 190 INDX=INDX1,INDX2
IF(INDX .EQ. INDX1) GO TO 180
INDXR1 = INDX1
INDXR2 = INDX - 1
INDXC1 = JU(JL(INDX))
INDXC2 = JU(JL(INDX)+1) - 1
IF(INDXC1 .GT. INDXC2) GO TO 180
160 KR = JL(INDXR1)
170 KC = IU(INDXC1)
IF(KR .GT. KC) THEN
INDXC1 = INDXC1 + 1
IF(INDXC1 .LE. INDXC2) GO TO 170
ELSEIF(KR .LT. KC) THEN
INDXR1 = INDXR1 + 1
IF(INDXR1 .LE. INDXR2) GO TO 160
ELSEIF(KR .EQ. KC) THEN
L(INDX) = L(INDX) - L(INDXR1)*DINV(KC)*U(INDXC1)
INDXR1 = INDXR1 + 1
INDXC1 = INDXC1 + 1
IF(INDXR1 .LE. INDXR2 .AND. INDXC1 .LE. INDXC2) GO TO 160
ENDIF
180 L(INDX) = L(INDX)/DINV(JL(INDX))
190 CONTINUE
C
C I-th column of U
200 INDX1 = JU(I)
INDX2 = JU(I+1) - 1
IF(INDX1 .GT. INDX2) GO TO 260
DO 250 INDX=INDX1,INDX2
IF(INDX .EQ. INDX1) GO TO 240
INDXC1 = INDX1
INDXC2 = INDX - 1
INDXR1 = IL(IU(INDX))
INDXR2 = IL(IU(INDX)+1) - 1
IF(INDXR1 .GT. INDXR2) GO TO 240
210 KR = JL(INDXR1)
220 KC = IU(INDXC1)
IF(KR .GT. KC) THEN
INDXC1 = INDXC1 + 1
IF(INDXC1 .LE. INDXC2) GO TO 220
ELSEIF(KR .LT. KC) THEN
INDXR1 = INDXR1 + 1
IF(INDXR1 .LE. INDXR2) GO TO 210
ELSEIF(KR .EQ. KC) THEN
U(INDX) = U(INDX) - L(INDXR1)*DINV(KC)*U(INDXC1)
INDXR1 = INDXR1 + 1
INDXC1 = INDXC1 + 1
IF(INDXR1 .LE. INDXR2 .AND. INDXC1 .LE. INDXC2) GO TO 210
ENDIF
240 U(INDX) = U(INDX)/DINV(IU(INDX))
250 CONTINUE
C
C I-th diagonal element
260 INDXR1 = IL(I)
INDXR2 = IL(I+1) - 1
IF(INDXR1 .GT. INDXR2) GO TO 300
INDXC1 = JU(I)
INDXC2 = JU(I+1) - 1
IF(INDXC1 .GT. INDXC2) GO TO 300
270 KR = JL(INDXR1)
280 KC = IU(INDXC1)
IF(KR .GT. KC) THEN
INDXC1 = INDXC1 + 1
IF(INDXC1 .LE. INDXC2) GO TO 280
ELSEIF(KR .LT. KC) THEN
INDXR1 = INDXR1 + 1
IF(INDXR1 .LE. INDXR2) GO TO 270
ELSEIF(KR .EQ. KC) THEN
DINV(I) = DINV(I) - L(INDXR1)*DINV(KC)*U(INDXC1)
INDXR1 = INDXR1 + 1
INDXC1 = INDXC1 + 1
IF(INDXR1 .LE. INDXR2 .AND. INDXC1 .LE. INDXC2) GO TO 270
ENDIF
C
300 CONTINUE
C
C Replace diagonal elements by their inverses.
CVD$ VECTOR
DO 430 I=1,N
DINV(I) = 1.0D0/DINV(I)
430 CONTINUE
C
RETURN
C------------- LAST LINE OF DSILUS FOLLOWS ----------------------------
END