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NAG[f07hrc] NAG[nag_zpbtrf] - Cholesky factorization of complex Hermitian positive-definite band matrix
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Calling Sequence
f07hrc(uplo, kd, ab, 'n'=n, 'fail'=fail)
nag_zpbtrf(. . .)
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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kd - integer;
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On entry: , the number of superdiagonals or subdiagonals of the matrix .
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Constraint: . .
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ab - Matrix(1..dim1, 1..dim2, datatype=complex[8], order=order);
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Note: this array may be supplied in Fortran_order or C_order , as specified by order. All array parameters must use a consistent order.
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'n'=n - integer; (optional)
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Default value: the second dimension of the array ab.
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On entry: , the order of the matrix .
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Constraint: . .
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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_zpbtrf (f07hrc) computes the Cholesky factorization of a complex Hermitian positive-definite band matrix.
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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: .
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 matrix is not positive-definite.
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Further Comments
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The total number of real floating-point operations is approximately , assuming .
A call to nag_zpbtrf (f07hrc) may be followed by calls to the functions:
The real analogue of this function is f07hdc (nag_dpbtrf).
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Examples
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>
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uplo := "Nag_Lower":
n := 4:
kd := 1:
ab := Matrix([[0 +0*I , 9.390000000000001 +0*I , 1.08 +1.73*I , 1.69 +0*I ], [-0.04 -0.29*I , 2.65 +0*I , -0.33 -2.24*I , 2.17 +0*I ]], datatype=complex[8], order='C_order'):
NAG:-f07hrc(uplo, kd, ab, 'n' = n):
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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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