*DECK DSPDI SUBROUTINE DSPDI (AP, N, KPVT, DET, INERT, WORK, JOB) C***BEGIN PROLOGUE DSPDI C***PURPOSE Compute the determinant, inertia, inverse of a real C symmetric matrix stored in packed form using the factors C from DSPFA. C***LIBRARY SLATEC (LINPACK) C***CATEGORY D2B1A, D3B1A C***TYPE DOUBLE PRECISION (SSPDI-S, DSPDI-D, CHPDI-C, CSPDI-C) C***KEYWORDS DETERMINANT, INVERSE, LINEAR ALGEBRA, LINPACK, MATRIX, C PACKED, SYMMETRIC C***AUTHOR Bunch, J., (UCSD) C***DESCRIPTION C C DSPDI computes the determinant, inertia and inverse C of a double precision symmetric matrix using the factors from C DSPFA, where the matrix is stored in packed form. C C On Entry C C AP DOUBLE PRECISION (N*(N+1)/2) C the output from DSPFA. C C N INTEGER C the order of the matrix A. C C KPVT INTEGER(N) C the pivot vector from DSPFA. C C WORK DOUBLE PRECISION(N) C work vector. Contents ignored. C C JOB INTEGER C JOB has the decimal expansion ABC where C if C .NE. 0, the inverse is computed, C if B .NE. 0, the determinant is computed, C if A .NE. 0, the inertia is computed. C C For example, JOB = 111 gives all three. C C On Return C C Variables not requested by JOB are not used. C C AP contains the upper triangle of the inverse of C the original matrix, stored in packed form. C The columns of the upper triangle are stored C sequentially in a one-dimensional array. C C DET DOUBLE PRECISION(2) C determinant of original matrix. C DETERMINANT = DET(1) * 10.0**DET(2) C with 1.0 .LE. ABS(DET(1)) .LT. 10.0 C or DET(1) = 0.0. C C INERT INTEGER(3) C the inertia of the original matrix. C INERT(1) = number of positive eigenvalues. C INERT(2) = number of negative eigenvalues. C INERT(3) = number of zero eigenvalues. C C Error Condition C C A division by zero will occur if the inverse is requested C and DSPCO has set RCOND .EQ. 0.0 C or DSPFA has set INFO .NE. 0 . C C***REFERENCES J. J. Dongarra, J. R. Bunch, C. B. Moler, and G. W. C Stewart, LINPACK Users' Guide, SIAM, 1979. C***ROUTINES CALLED DAXPY, DCOPY, DDOT, DSWAP C***REVISION HISTORY (YYMMDD) C 780814 DATE WRITTEN C 890531 Changed all specific intrinsics to generic. (WRB) C 890831 Modified array declarations. (WRB) C 891107 Modified routine equivalence list. (WRB) C 891107 REVISION DATE from Version 3.2 C 891214 Prologue converted to Version 4.0 format. (BAB) C 900326 Removed duplicate information from DESCRIPTION section. C (WRB) C 920501 Reformatted the REFERENCES section. (WRB) C***END PROLOGUE DSPDI INTEGER N,JOB DOUBLE PRECISION AP(*),WORK(*) DOUBLE PRECISION DET(2) INTEGER KPVT(*),INERT(3) C DOUBLE PRECISION AKKP1,DDOT,TEMP DOUBLE PRECISION TEN,D,T,AK,AKP1 INTEGER IJ,IK,IKP1,IKS,J,JB,JK,JKP1 INTEGER K,KK,KKP1,KM1,KS,KSJ,KSKP1,KSTEP LOGICAL NOINV,NODET,NOERT C***FIRST EXECUTABLE STATEMENT DSPDI NOINV = MOD(JOB,10) .EQ. 0 NODET = MOD(JOB,100)/10 .EQ. 0 NOERT = MOD(JOB,1000)/100 .EQ. 0 C IF (NODET .AND. NOERT) GO TO 140 IF (NOERT) GO TO 10 INERT(1) = 0 INERT(2) = 0 INERT(3) = 0 10 CONTINUE IF (NODET) GO TO 20 DET(1) = 1.0D0 DET(2) = 0.0D0 TEN = 10.0D0 20 CONTINUE T = 0.0D0 IK = 0 DO 130 K = 1, N KK = IK + K D = AP(KK) C C CHECK IF 1 BY 1 C IF (KPVT(K) .GT. 0) GO TO 50 C C 2 BY 2 BLOCK C USE DET (D S) = (D/T * C - T) * T , T = ABS(S) C (S C) C TO AVOID UNDERFLOW/OVERFLOW TROUBLES. C TAKE TWO PASSES THROUGH SCALING. USE T FOR FLAG. C IF (T .NE. 0.0D0) GO TO 30 IKP1 = IK + K KKP1 = IKP1 + K T = ABS(AP(KKP1)) D = (D/T)*AP(KKP1+1) - T GO TO 40 30 CONTINUE D = T T = 0.0D0 40 CONTINUE 50 CONTINUE C IF (NOERT) GO TO 60 IF (D .GT. 0.0D0) INERT(1) = INERT(1) + 1 IF (D .LT. 0.0D0) INERT(2) = INERT(2) + 1 IF (D .EQ. 0.0D0) INERT(3) = INERT(3) + 1 60 CONTINUE C IF (NODET) GO TO 120 DET(1) = D*DET(1) IF (DET(1) .EQ. 0.0D0) GO TO 110 70 IF (ABS(DET(1)) .GE. 1.0D0) GO TO 80 DET(1) = TEN*DET(1) DET(2) = DET(2) - 1.0D0 GO TO 70 80 CONTINUE 90 IF (ABS(DET(1)) .LT. TEN) GO TO 100 DET(1) = DET(1)/TEN DET(2) = DET(2) + 1.0D0 GO TO 90 100 CONTINUE 110 CONTINUE 120 CONTINUE IK = IK + K 130 CONTINUE 140 CONTINUE C C COMPUTE INVERSE(A) C IF (NOINV) GO TO 270 K = 1 IK = 0 150 IF (K .GT. N) GO TO 260 KM1 = K - 1 KK = IK + K IKP1 = IK + K KKP1 = IKP1 + K IF (KPVT(K) .LT. 0) GO TO 180 C C 1 BY 1 C AP(KK) = 1.0D0/AP(KK) IF (KM1 .LT. 1) GO TO 170 CALL DCOPY(KM1,AP(IK+1),1,WORK,1) IJ = 0 DO 160 J = 1, KM1 JK = IK + J AP(JK) = DDOT(J,AP(IJ+1),1,WORK,1) CALL DAXPY(J-1,WORK(J),AP(IJ+1),1,AP(IK+1),1) IJ = IJ + J 160 CONTINUE AP(KK) = AP(KK) + DDOT(KM1,WORK,1,AP(IK+1),1) 170 CONTINUE KSTEP = 1 GO TO 220 180 CONTINUE C C 2 BY 2 C T = ABS(AP(KKP1)) AK = AP(KK)/T AKP1 = AP(KKP1+1)/T AKKP1 = AP(KKP1)/T D = T*(AK*AKP1 - 1.0D0) AP(KK) = AKP1/D AP(KKP1+1) = AK/D AP(KKP1) = -AKKP1/D IF (KM1 .LT. 1) GO TO 210 CALL DCOPY(KM1,AP(IKP1+1),1,WORK,1) IJ = 0 DO 190 J = 1, KM1 JKP1 = IKP1 + J AP(JKP1) = DDOT(J,AP(IJ+1),1,WORK,1) CALL DAXPY(J-1,WORK(J),AP(IJ+1),1,AP(IKP1+1),1) IJ = IJ + J 190 CONTINUE AP(KKP1+1) = AP(KKP1+1) 1 + DDOT(KM1,WORK,1,AP(IKP1+1),1) AP(KKP1) = AP(KKP1) 1 + DDOT(KM1,AP(IK+1),1,AP(IKP1+1),1) CALL DCOPY(KM1,AP(IK+1),1,WORK,1) IJ = 0 DO 200 J = 1, KM1 JK = IK + J AP(JK) = DDOT(J,AP(IJ+1),1,WORK,1) CALL DAXPY(J-1,WORK(J),AP(IJ+1),1,AP(IK+1),1) IJ = IJ + J 200 CONTINUE AP(KK) = AP(KK) + DDOT(KM1,WORK,1,AP(IK+1),1) 210 CONTINUE KSTEP = 2 220 CONTINUE C C SWAP C KS = ABS(KPVT(K)) IF (KS .EQ. K) GO TO 250 IKS = (KS*(KS - 1))/2 CALL DSWAP(KS,AP(IKS+1),1,AP(IK+1),1) KSJ = IK + KS DO 230 JB = KS, K J = K + KS - JB JK = IK + J TEMP = AP(JK) AP(JK) = AP(KSJ) AP(KSJ) = TEMP KSJ = KSJ - (J - 1) 230 CONTINUE IF (KSTEP .EQ. 1) GO TO 240 KSKP1 = IKP1 + KS TEMP = AP(KSKP1) AP(KSKP1) = AP(KKP1) AP(KKP1) = TEMP 240 CONTINUE 250 CONTINUE IK = IK + K IF (KSTEP .EQ. 2) IK = IK + K + 1 K = K + KSTEP GO TO 150 260 CONTINUE 270 CONTINUE RETURN END