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NAG[f07brc] NAG[nag_zgbtrf] - factorization of complex by band matrix
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Calling Sequence
f07brc(kl, ku, ab, ipiv, 'm'=m, 'n'=n, 'fail'=fail)
nag_zgbtrf(. . .)
Parameters
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kl - integer;
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On entry: , the number of subdiagonals within the band of the matrix .
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Constraint: . .
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ku - integer;
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On entry: , the number of superdiagonals within the band 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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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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'm'=m - integer; (optional)
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Default value: the first dimension of the array ab.
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On entry: , the number of rows of the matrix .
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Constraint: . .
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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 number of columns 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_zgbtrf (f07brc) computes the factorization of a complex by band 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: .
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.
"NE_SINGULAR"
The factor is exactly singular.
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Further Comments
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The total number of real floating-point operations varies between approximately and , depending on the interchanges, assuming and .
A call to nag_zgbtrf (f07brc) may be followed by calls to the functions:
The real analogue of this function is f07bdc (nag_dgbtrf).
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Examples
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>
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m := 4:
n := 4:
kl := 1:
ku := 2:
ab := Matrix([[0 +0*I , -1.65 +2.26*I , -2.05 -0.85*I , 0.97 -2.84*I , 0 +0*I ], [0 +6.3*I , -1.48 -1.75*I , -3.99 +4.01*I , 0.59 -0.48*I , 0 +0*I ], [-0.77 +2.83*I , -1.06 +1.94*I , 3.33 -1.04*I , 0 +0*I , 0 +0*I ], [4.48 -1.09*I , -0.46 -1.72*I , 0 +0*I , 0 +0*I , 0 +0*I ]], datatype=complex[8], order='C_order'):
ipiv := Vector(4, datatype=integer[kernelopts('wordsize')/8]):
NAG:-f07brc(kl, ku, ab, ipiv, 'm' = m, 'n' = n):
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