NAG Library Routine Document

F08GTF (ZUPGTR)

1  Purpose

2  Specification

3  Description

4  References

5  Parameters

1:     $\mathrm{UPLO}$ – CHARACTER(1)Input

On entry: this must be the same parameter UPLO as supplied to F08GSF (ZHPTRD).

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

2:     $\mathrm{N}$ – INTEGERInput

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

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

3:     $\mathrm{AP}\left(*\right)$ – 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:     $\mathrm{TAU}\left(*\right)$ – 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:     $\mathrm{Q}\left(\mathbf{LDQ},*\right)$ – 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:     $\mathrm{LDQ}$ – 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:     $\mathrm{WORK}\left(\mathbf{N}-1\right)$ – COMPLEX (KIND=nag_wp) arrayWorkspace

8:     $\mathrm{INFO}$ – 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)