# sopmtr (3) - Linux Manuals

sopmtr.f -

## SYNOPSIS

### Functions/Subroutines

subroutine sopmtr (SIDE, UPLO, TRANS, M, N, AP, TAU, C, LDC, WORK, INFO)
SOPMTR

## Function/Subroutine Documentation

### subroutine sopmtr (characterSIDE, characterUPLO, characterTRANS, integerM, integerN, real, dimension( * )AP, real, dimension( * )TAU, real, dimension( ldc, * )C, integerLDC, real, dimension( * )WORK, integerINFO)

SOPMTR

Purpose:

``` SOPMTR overwrites the general real M-by-N matrix C with

SIDE = 'L'     SIDE = 'R'
TRANS = 'N':      Q * C          C * Q
TRANS = 'T':      Q**T * C       C * Q**T

where Q is a real orthogonal matrix of order nq, with nq = m if
SIDE = 'L' and nq = n if SIDE = 'R'. Q is defined as the product of
nq-1 elementary reflectors, as returned by SSPTRD using packed
storage:

if UPLO = 'U', Q = H(nq-1) . . . H(2) H(1);

if UPLO = 'L', Q = H(1) H(2) . . . H(nq-1).
```

Parameters:

SIDE

```          SIDE is CHARACTER*1
= 'L': apply Q or Q**T from the Left;
= 'R': apply Q or Q**T from the Right.
```

UPLO

```          UPLO is CHARACTER*1
= 'U': Upper triangular packed storage used in previous
call to SSPTRD;
= 'L': Lower triangular packed storage used in previous
call to SSPTRD.
```

TRANS

```          TRANS is CHARACTER*1
= 'N':  No transpose, apply Q;
= 'T':  Transpose, apply Q**T.
```

M

```          M is INTEGER
The number of rows of the matrix C. M >= 0.
```

N

```          N is INTEGER
The number of columns of the matrix C. N >= 0.
```

AP

```          AP is REAL array, dimension
(M*(M+1)/2) if SIDE = 'L'
(N*(N+1)/2) if SIDE = 'R'
The vectors which define the elementary reflectors, as
returned by SSPTRD.  AP is modified by the routine but
restored on exit.
```

TAU

```          TAU is REAL array, dimension (M-1) if SIDE = 'L'
or (N-1) if SIDE = 'R'
TAU(i) must contain the scalar factor of the elementary
reflector H(i), as returned by SSPTRD.
```

C

```          C is REAL array, dimension (LDC,N)
On entry, the M-by-N matrix C.
On exit, C is overwritten by Q*C or Q**T*C or C*Q**T or C*Q.
```

LDC

```          LDC is INTEGER
The leading dimension of the array C. LDC >= max(1,M).
```

WORK

```          WORK is REAL array, dimension
(N) if SIDE = 'L'
(M) if SIDE = 'R'
```

INFO

```          INFO is INTEGER
= 0:  successful exit
< 0:  if INFO = -i, the i-th argument had an illegal value
```

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

November 2011

Definition at line 150 of file sopmtr.f.

## Author

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