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LAPACK
3.7.0
LAPACK: Linear Algebra PACKage
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subroutine sppcon | ( | character | UPLO, |
integer | N, | ||
real, dimension( * ) | AP, | ||
real | ANORM, | ||
real | RCOND, | ||
real, dimension( * ) | WORK, | ||
integer, dimension( * ) | IWORK, | ||
integer | INFO | ||
) |
SPPCON
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SPPCON estimates the reciprocal of the condition number (in the 1-norm) of a real symmetric positive definite packed matrix using the Cholesky factorization A = U**T*U or A = L*L**T computed by SPPTRF. An estimate is obtained for norm(inv(A)), and the reciprocal of the condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))).
[in] | UPLO | UPLO is CHARACTER*1 = 'U': Upper triangle of A is stored; = 'L': Lower triangle of A is stored. |
[in] | N | N is INTEGER The order of the matrix A. N >= 0. |
[in] | AP | AP is REAL array, dimension (N*(N+1)/2) The triangular factor U or L from the Cholesky factorization A = U**T*U or A = L*L**T, packed columnwise in a linear array. The j-th column of U or L is stored in the array AP as follows: if UPLO = 'U', AP(i + (j-1)*j/2) = U(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = L(i,j) for j<=i<=n. |
[in] | ANORM | ANORM is REAL The 1-norm (or infinity-norm) of the symmetric matrix A. |
[out] | RCOND | RCOND is REAL 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. |
[out] | WORK | WORK is REAL array, dimension (3*N) |
[out] | IWORK | IWORK is INTEGER array, dimension (N) |
[out] | INFO | INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value |
Definition at line 120 of file sppcon.f.