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NAG[f16rbc] NAG[nag_dgb_norm] -  -norm,  -norm, Frobenius norm, largest absolute element, real band matrix
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Calling Sequence
f16rbc(norm_type, m, kl, ku, ab, r, 'n'=n, 'fail'=fail)
nag_dgb_norm(. . .)
Parameters
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norm_type - String;
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On entry: specifies the value to be returned.
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  or "Nag_OneNorm" The 1-norm.
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 The  -norm.
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 The Frobenius (or Euclidean) norm.
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 The value ![max |a[ij]|](/support/helpjp/helpview.aspx?si=10268/file08336/math41.png) (not a norm).
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Constraint:   "Nag_OneNorm", "Nag_InfNorm", "Nag_FrobeniusNorm" or "Nag_MaxNorm". .
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m - integer;
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On entry:  , the number of rows of the matrix  .
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Constraint:  . .
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kl - integer;
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On entry: ![k[l]](/support/helpjp/helpview.aspx?si=10268/file08336/math71.png) , the number of subdiagonals within the band of  .
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Constraint:  . .
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ku - integer;
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On entry: ![k[u]](/support/helpjp/helpview.aspx?si=10268/file08336/math86.png) , the number of superdiagonals within the band of  .
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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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r - assignable;
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Note: On exit the variable r will have a value of type float.
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On exit: the value of the norm specified by norm.
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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_dgb_norm (f16rbc) calculates the value of the 1-norm, the  -norm, the Frobenius norm or the maximum absolute value of the elements of a real  by  band matrix.
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Description
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Given a real  by  band matrix,  , nag_dgb_norm (f16rbc) calculates one of the values given by
![||A||[F]=((∑),(∑)|a[ij]|^2)^(1/2)](/support/helpjp/helpview.aspx?si=10268/file08336/math218.png)
or
![max |a[ij]|](/support/helpjp/helpview.aspx?si=10268/file08336/math222.png)
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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:  .
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Accuracy
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The BLAS standard requires accurate implementations which avoid unnecessary over/underflow (see Section 2.7 of The BLAS Technical Forum Standard (2001)).
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Examples
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norm_type := "Nag_OneNorm":
kl := 2:
ku := 1:
m := 6:
ab := Matrix([[0,1,2,3],[1,2,3,4],[2,3,4,5],[3,4,5,6]], datatype=float[8], order='Fortran_order'):
NAG:-f16rbc(norm_type, m, kl, ku, ab, r):
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