1DSPCON(1) LAPACK routine (version 3.2) DSPCON(1)
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6 DSPCON - estimates the reciprocal of the condition number (in the
7 1-norm) of a real symmetric packed matrix A using the factorization A =
8 U*D*U**T or A = L*D*L**T computed by DSPTRF
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11 SUBROUTINE DSPCON( UPLO, N, AP, IPIV, ANORM, RCOND, WORK, IWORK, INFO )
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13 CHARACTER UPLO
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15 INTEGER INFO, N
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17 DOUBLE PRECISION ANORM, RCOND
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19 INTEGER IPIV( * ), IWORK( * )
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21 DOUBLE PRECISION AP( * ), WORK( * )
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24 DSPCON estimates the reciprocal of the condition number (in the 1-norm)
25 of a real symmetric packed matrix A using the factorization A =
26 U*D*U**T or A = L*D*L**T computed by DSPTRF. An estimate is obtained
27 for norm(inv(A)), and the reciprocal of the condition number is com‐
28 puted as RCOND = 1 / (ANORM * norm(inv(A))).
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31 UPLO (input) CHARACTER*1
32 Specifies whether the details of the factorization are stored
33 as an upper or lower triangular matrix. = 'U': Upper triangu‐
34 lar, form is A = U*D*U**T;
35 = 'L': Lower triangular, form is A = L*D*L**T.
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37 N (input) INTEGER
38 The order of the matrix A. N >= 0.
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40 AP (input) DOUBLE PRECISION array, dimension (N*(N+1)/2)
41 The block diagonal matrix D and the multipliers used to obtain
42 the factor U or L as computed by DSPTRF, stored as a packed
43 triangular matrix.
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45 IPIV (input) INTEGER array, dimension (N)
46 Details of the interchanges and the block structure of D as
47 determined by DSPTRF.
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49 ANORM (input) DOUBLE PRECISION
50 The 1-norm of the original matrix A.
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52 RCOND (output) DOUBLE PRECISION
53 The reciprocal of the condition number of the matrix A, com‐
54 puted as RCOND = 1/(ANORM * AINVNM), where AINVNM is an esti‐
55 mate of the 1-norm of inv(A) computed in this routine.
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57 WORK (workspace) DOUBLE PRECISION array, dimension (2*N)
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59 IWORK (workspace) INTEGER array, dimension (N)
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61 INFO (output) INTEGER
62 = 0: successful exit
63 < 0: if INFO = -i, the i-th argument had an illegal value
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67 LAPACK routine (version 3.2) November 2008 DSPCON(1)