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NAG[f07hec] NAG[nag_dpbtrs] - Solution of real symmetric positive-definite band system of linear equations, multiple right-hand sides, matrix already factorized by f07hdc (nag_dpbtrf)
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Calling Sequence
f07hec(uplo, kd, ab, b, 'n'=n, 'nrhs'=nrhs, 'fail'=fail)
nag_dpbtrs(. . .)
Parameters
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uplo - String;
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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=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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b - 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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'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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'nrhs'=nrhs - integer; (optional)
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Default value: the second dimension of the array b.
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On entry: , the number of right-hand sides.
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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_dpbtrs (f07hec) solves a real symmetric positive-definite band system of linear equations with multiple right-hand sides,
where has been factorized by f07hdc (nag_dpbtrf).
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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: .
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.
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Further Comments
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The total number of floating-point operations is approximately , assuming .
This function may be followed by a call to f07hhc (nag_dpbrfs) to refine the solution and return an error estimate.
The complex analogue of this function is f07hsc (nag_zpbtrs).
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Examples
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>
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uplo := "Nag_Lower":
n := 4:
kd := 1:
nrhs := 2:
ab := Matrix([[0, 2.343074902771996, 1.143796127400537, 2.078877201506509], [-1.149659055507477, 1.130612248337004, -1.963537900164584, 1.146524711734229]], datatype=float[8], order='C_order'):
b := Matrix([[22.09, 5.1], [9.31, 30.81], [-5.24, -25.82], [11.83, 22.9]], datatype=float[8], order='C_order'):
NAG:-f07hec(uplo, kd, ab, b, 'n' = n, 'nrhs' = nrhs):
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