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NAG[f07mdc] NAG[nag_dsytrf] - Bunch–Kaufman factorization of real symmetric indefinite matrix
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Calling Sequence
f07mdc(uplo, a, ipiv, 'n'=n, 'fail'=fail)
nag_dsytrf(. . .)
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 to be factorized.
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Constraint: "Nag_Upper" or "Nag_Lower". .
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a - Matrix(1..dim1, 1..dim2, datatype=float[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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If , the upper triangle of must be stored and the elements of the array below the diagonal are not referenced.
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If , the lower triangle of must be stored and the elements of the array above the diagonal are not referenced.
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ipiv - Vector(1..dim, datatype=integer[kernelopts('wordsize')/8]);
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Note: the dimension, dim, of the array ipiv must be at least .
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On exit: details of the interchanges and the block structure of . More precisely,
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'n'=n - integer; (optional)
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Default value: the dimension of the array a.
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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_dsytrf (f07mdc) computes the Bunch–Kaufman factorization of a real symmetric indefinite matrix.
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Error Indicators and Warnings
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"NE_ALLOC_FAIL"
Dynamic memory allocation failed.
"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_SINGULAR"
The block diagonal matrix is exactly singular.
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Examples
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>
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uplo := "Nag_Upper":
n := 4:
a := Matrix([[2.07, 3.87, 4.2, -1.15], [0, -0.21, 1.87, 0.63], [0, 0, 1.15, 2.06], [0, 0, 0, -1.81]], datatype=float[8], order='C_order'):
ipiv := Vector(4, datatype=integer[kernelopts('wordsize')/8]):
NAG:-f07mdc(uplo, a, ipiv, 'n' = n):
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