NAG Library Routine Document

f08gtf  (zupgtr)

1

Purpose

2

Specification

3

Description

4

References

5

Arguments

1:     $\mathbf{uplo}$ – Character(1)Input

On entry: this must be the same argument uplo as supplied to f08gsf (zhptrd).

Constraint: $\mathbf{uplo}=\text{'U'}$ or $\text{'L'}$.

2:     $\mathbf{n}$ – IntegerInput

On entry: $n$, the order of the matrix $Q$.

Constraint: $\mathbf{n}\ge 0$.

3:     $\mathbf{ap}\left(*\right)$ – Complex (Kind=nag_wp) arrayInput

Note: the dimension of the array ap must be at least $\max \left(1,\mathbf{n}\times \left(\mathbf{n}+1\right)/2\right)$.

On entry: details of the vectors which define the elementary reflectors, as returned by f08gsf (zhptrd).

4:     $\mathbf{tau}\left(*\right)$ – Complex (Kind=nag_wp) arrayInput

Note: the dimension of the array tau must be at least $\max \left(1,\mathbf{n}-1\right)$.

On entry: further details of the elementary reflectors, as returned by f08gsf (zhptrd).

5:     $\mathbf{q}\left(\mathbf{ldq},*\right)$ – Complex (Kind=nag_wp) arrayOutput

Note: the second dimension of the array q must be at least $\max \left(1,\mathbf{n}\right)$.

On exit: the $n$ by $n$ unitary matrix $Q$.

6:     $\mathbf{ldq}$ – IntegerInput

On entry: the first dimension of the array q as declared in the (sub)program from which f08gtf (zupgtr) is called.

Constraint: $\mathbf{ldq}\ge \max \left(1,\mathbf{n}\right)$.

7:     $\mathbf{work}\left(\mathbf{n}-1\right)$ – Complex (Kind=nag_wp) arrayWorkspace

8:     $\mathbf{info}$ – IntegerOutput

On exit: $\mathbf{info}=0$ unless the routine detects an error (see Section 6).

6

Error Indicators and Warnings

$\mathbf{info}<0$

If $\mathbf{info}=-i$, argument $i$ had an illegal value. An explanatory message is output, and execution of the program is terminated.

7

Accuracy

8

Parallelism and Performance

9

Further Comments

10

Example

10.1

Program Text

Program Text (f08gtfe.f90)

10.2

Program Data

Program Data (f08gtfe.d)

10.3

Program Results

Program Results (f08gtfe.r)