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SUBROUTINE SSICO(A,LDA,N,KPVT,RCOND,Z)
INTEGER LDA,N,KPVT(1)
REAL A(LDA,1),Z(1)
REAL RCOND
C
C SSICO FACTORS A REAL SYMMETRIC MATRIX BY ELIMINATION WITH
C SYMMETRIC PIVOTING AND ESTIMATES THE CONDITION OF THE MATRIX.
C
C IF RCOND IS NOT NEEDED, SSIFA IS SLIGHTLY FASTER.
C TO SOLVE A*X = B , FOLLOW SSICO BY SSISL.
C TO COMPUTE INVERSE(A)*C , FOLLOW SSICO BY SSISL.
C TO COMPUTE INVERSE(A) , FOLLOW SSICO BY SSIDI.
C TO COMPUTE DETERMINANT(A) , FOLLOW SSICO BY SSIDI.
C TO COMPUTE INERTIA(A), FOLLOW SSICO BY SSIDI.
C
C ON ENTRY
C
C A REAL(LDA, N)
C THE SYMMETRIC MATRIX TO BE FACTORED.
C ONLY THE DIAGONAL AND UPPER TRIANGLE ARE USED.
C
C LDA INTEGER
C THE LEADING DIMENSION OF THE ARRAY A .
C
C N INTEGER
C THE ORDER OF THE MATRIX A .
C
C OUTPUT
C
C A A BLOCK DIAGONAL MATRIX AND THE MULTIPLIERS WHICH
C WERE USED TO OBTAIN IT.
C THE FACTORIZATION CAN BE WRITTEN A = U*D*TRANS(U)
C WHERE U IS A PRODUCT OF PERMUTATION AND UNIT
C UPPER TRIANGULAR MATRICES , TRANS(U) IS THE
C TRANSPOSE OF U , AND D IS BLOCK DIAGONAL
C WITH 1 BY 1 AND 2 BY 2 BLOCKS.
C
C KPVT INTEGER(N)
C AN INTEGER VECTOR OF PIVOT INDICES.
C
C RCOND REAL
C AN ESTIMATE OF THE RECIPROCAL CONDITION OF A .
C FOR THE SYSTEM A*X = B , RELATIVE PERTURBATIONS
C IN A AND B OF SIZE EPSILON MAY CAUSE
C RELATIVE PERTURBATIONS IN X OF SIZE EPSILON/RCOND
C IF RCOND IS SO SMALL THAT THE LOGICAL EXPRESSION
C 1.0 + RCOND .EQ. 1.0
C IS TRUE, THEN A MAY BE SINGULAR TO WORKING
C PRECISION. IN PARTICULAR, RCOND IS ZERO IF
C EXACT SINGULARITY IS DETECTED OR THE ESTIMATE
C UNDERFLOWS.
C
C Z REAL(N)
C A WORK VECTOR WHOSE CONTENTS ARE USUALLY UNIMPORTANT
C IF A IS CLOSE TO A SINGULAR MATRIX, THEN Z IS
C AN APPROXIMATE NULL VECTOR IN THE SENSE THAT
C NORM(A*Z) = RCOND*NORM(A)*NORM(Z) .
C
C LINPACK. THIS VERSION DATED 08/14/78 .
C CLEVE MOLER, UNIVERSITY OF NEW MEXICO, ARGONNE NATIONAL LAB.
C
C SUBROUTINES AND FUNCTIONS
C
C LINPACK SSIFA
C BLAS SAXPY,SDOT,SSCAL,SASUM
C FORTRAN ABS,AMAX1,IABS,SIGN
C