|
NAG[f07pdc] NAG[nag_dsptrf] - Bunch–Kaufman factorization of real symmetric indefinite matrix, packed storage
|
|
Calling Sequence
f07pdc(uplo, n, ap, ipiv, 'fail'=fail)
nag_dsptrf(. . .)
Parameters
|
uplo - String;
|
|
|
On entry: indicates whether the upper or lower triangular part of is stored and how is to be factorized.
|
|
Constraint: "Nag_Upper" or "Nag_Lower". .
|
|
|
n - integer;
|
|
|
On entry: , the order of the matrix .
|
|
Constraint: . .
|
|
|
ap - Vector(1..dim, datatype=float[8]);
|
|
|
Note: the dimension, dim, of the array ap must be at least .
|
|
On entry: the symmetric indefinite matrix , packed by rows or columns. The storage of elements depends on the storage order and uplo arguments as follows:
|
|
|
ipiv - Vector(1..dim, datatype=integer[kernelopts('wordsize')/8]);
|
|
|
Note: the dimension, dim, of the array ipiv must be at least .
|
|
On exit: details of the interchanges and the block structure of . More precisely,
|
|
|
'fail'=fail - table; (optional)
|
|
|
The NAG error argument, see the documentation for NagError.
|
|
|
|
Description
|
|
|
Purpose
|
|
nag_dsptrf (f07pdc) computes the Bunch–Kaufman factorization of a real symmetric indefinite matrix, using packed storage.
|
|
Error Indicators and Warnings
|
|
"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.
|
|
|
Examples
|
|
>
|
uplo := "Nag_Upper":
n := 4:
ap := Vector([2.07, 3.87, 4.2, -1.15, -0.21, 1.87, 0.63, 1.15, 2.06, -1.81], datatype=float[8], order='C_order'):
ipiv := Vector(4, datatype=integer[kernelopts('wordsize')/8]):
NAG:-f07pdc(uplo, n, ap, ipiv):
|
|
|