GNU/Linux man pages
Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :
GNU/Linux |
CentOS 4.8 |
i386 |
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dsycon(l) |
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DSYCON - estimate the reciprocal of the condition number (in the 1-norm) of a real symmetric matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by DSYTRF
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SUBROUTINE DSYCON( |
UPLO, N, A, LDA, IPIV, ANORM, RCOND, WORK, IWORK, INFO ) | ||
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CHARACTER |
UPLO | ||
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INTEGER |
INFO, LDA, N | ||
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DOUBLE |
PRECISION ANORM, RCOND | ||
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INTEGER |
IPIV( * ), IWORK( * ) | ||
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DOUBLE |
PRECISION A( LDA, * ), WORK( * ) |
DSYCON estimates the reciprocal of the condition number (in the 1-norm) of a real symmetric matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by DSYTRF. An estimate is obtained for norm(inv(A)), and the reciprocal of the condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))).
UPLO (input) CHARACTER*1
Specifies whether the details
of the factorization are stored as an upper or lower
triangular matrix. = ’U’: Upper triangular, form
is A = U*D*U**T;
= ’L’: Lower triangular, form is A =
L*D*L**T.
N (input) INTEGER
The order of the matrix A. N >= 0.
A (input) DOUBLE PRECISION array, dimension (LDA,N)
The block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by DSYTRF.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
IPIV (input) INTEGER array, dimension (N)
Details of the interchanges and the block structure of D as determined by DSYTRF.
ANORM (input) DOUBLE PRECISION
The 1-norm of the original matrix A.
RCOND (output) DOUBLE PRECISION
The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is an estimate of the 1-norm of inv(A) computed in this routine.
WORK (workspace) DOUBLE
PRECISION array, dimension (2*N)
IWORK (workspace) INTEGER array, dimension (N)
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal
value
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dsycon(l) | |