dspco
dspco - (obsolete) compute the UDU factorization and condition number of a symmetric
matrix A in packed storage. If the condition number is not needed then
SSPFA is slightly faster. It is typical to follow a call to SSPCO with
a call to SSPSL to solve Ax = b or to SSPDI to compute the determinant,
inverse, and inertia of A.
SUBROUTINE DSPCO( A, N, IPIVOT, RCOND, WORK)
INTEGER N
INTEGER IPIVOT(*)
DOUBLE PRECISION RCOND
DOUBLE PRECISION A(*), WORK(*)
SUBROUTINE DSPCO_64( A, N, IPIVOT, RCOND, WORK)
INTEGER*8 N
INTEGER*8 IPIVOT(*)
DOUBLE PRECISION RCOND
DOUBLE PRECISION A(*), WORK(*)
#include <sunperf.h>
void dspco(double *a, int n, int *ipivot, double *rcond);
void dspco_64(double *a, long n, long *ipivot, double *rcond);
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* A (input/output)
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On entry, the upper triangle of the matrix A.
On exit, a UDU factorization of the matrix A.
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* N (input)
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Order of the matrix A. N >= 0.
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* IPIVOT (output)
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On exit, a vector of pivot indices.
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* RCOND (output)
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On exit, an estimate of the reciprocal condition number of A.
0.0 <= RCOND <= 1.0. As the value of RCOND gets smaller, operations with
A such as solving Ax = b may become less stable. If RCOND satisfies
RCOND + 1.0 = 1.0 then A may be singular to working precision.
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* WORK (workspace)
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Scratch array with a dimension of N.