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NAG[f07grc] NAG[nag_zpptrf] - Cholesky factorization of complex Hermitian positive-definite matrix, packed storage
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Calling Sequence
f07grc(uplo, n, ap, 'fail'=fail)
nag_zpptrf(. . .)
Parameters
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uplo - String;
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On entry: indicates whether the upper or lower triangular part of is stored and how is factorized.
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Constraint: "Nag_Upper" or "Nag_Lower". .
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n - integer;
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On entry: , the order of the matrix .
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Constraint: . .
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ap - Vector(1..dim, datatype=complex[8]);
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Note: the dimension, dim, of the array ap must be at least .
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On entry: the Hermitian positive-definite matrix , packed by rows or columns. The storage of elements depends on the storage order and uplo arguments as follows:
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'fail'=fail - table; (optional)
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The NAG error argument, see the documentation for NagError.
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Description
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Purpose
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nag_zpptrf (f07grc) computes the Cholesky factorization of a complex Hermitian positive-definite matrix, using packed storage.
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Error Indicators and Warnings
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"NE_BAD_PARAM"
On entry, argument had an illegal value.
"NE_INT"
On entry, . Constraint: .
"NE_INTERNAL_ERROR"
An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please consult NAG for assistance.
"NE_POS_DEF"
The leading minor of order is not positive-definite and the factorization could not be completed. Hence itself is not positive-definite. This may indicate an error in forming the matrix . To factorize a matrix which is not positive-definite, call f07prc (nag_zhptrf) instead.
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Further Comments
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The total number of real floating-point operations is approximately .
A call to nag_zpptrf (f07grc) may be followed by calls to the functions:
The real analogue of this function is f07gdc (nag_dpptrf).
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Examples
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>
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uplo := "Nag_Lower":
n := 4:
ap := Vector([3.23 +0*I, 1.51 +1.92*I, 3.58 +0*I, 1.9 -0.84*I, -0.23 -1.11*I, 4.09 +0*I, 0.42 -2.5*I, -1.18 -1.37*I, 2.33 +0.14*I, 4.29 +0*I], datatype=complex[8], order='C_order'):
NAG:-f07grc(uplo, n, ap):
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See Also
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Demmel J W (1989) On floating-point errors in Cholesky LAPACK Working Note No. 14 University of Tennessee, Knoxville
Golub G H and Van Loan C F (1996) Matrix Computations (3rd Edition) Johns Hopkins University Press, Baltimore
f07 Chapter Introduction.
NAG Toolbox Overview.
NAG Web Site.
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