Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

Contents

p?org2r/p?ung2r

Generates all or part of the orthogonal/unitary matrix Q from a QR factorization determined by
p?geqrf
 (unblocked algorithm).

Syntax

void
psorg2r
(
MKL_INT
*m
,
MKL_INT
*n
,
MKL_INT
*k
,
float
*a
,
MKL_INT
*ia
,
MKL_INT
*ja
,
MKL_INT
*desca
,
float
*tau
,
float
*work
,
MKL_INT
*lwork
,
MKL_INT
*info
);
void
pdorg2r
(
MKL_INT
*m
,
MKL_INT
*n
,
MKL_INT
*k
,
double
*a
,
MKL_INT
*ia
,
MKL_INT
*ja
,
MKL_INT
*desca
,
double
*tau
,
double
*work
,
MKL_INT
*lwork
,
MKL_INT
*info
);
void
pcung2r
(
MKL_INT
*m
,
MKL_INT
*n
,
MKL_INT
*k
,
MKL_Complex8
*a
,
MKL_INT
*ia
,
MKL_INT
*ja
,
MKL_INT
*desca
,
MKL_Complex8
*tau
,
MKL_Complex8
*work
,
MKL_INT
*lwork
,
MKL_INT
*info
);
void
pzung2r
(
MKL_INT
*m
,
MKL_INT
*n
,
MKL_INT
*k
,
MKL_Complex16
*a
,
MKL_INT
*ia
,
MKL_INT
*ja
,
MKL_INT
*desca
,
MKL_Complex16
*tau
,
MKL_Complex16
*work
,
MKL_INT
*lwork
,
MKL_INT
*info
);
Include Files
  • mkl_scalapack.h
Description
The
p?org2r/p?ung2r
function
generates an
m
-by-
n
 real/complex matrix
Q
 denoting
A
(
ia
:
ia
+
m
-1,
ja
:
ja
+
n
-1)
 with orthonormal columns, which is defined as the first
n
 columns of a product of
k
 elementary reflectors of order
m
:
Q
 =
H
(1)*
H
(2)*...*
H
(
k
)
as returned by
p?geqrf
.
Input Parameters
m
(global)
The number of rows in the distributed submatrix
Q.
m
≥
 0
.
n
(global)
The number of columns in the distributed submatrix
Q
.
m
≥
n
≥
 0
.
k
(global)
The number of elementary reflectors whose product defines the matrix
Q
.
n
≥
k
≥
 0
.
a
Pointer into the local memory to an array of size
lld_a
 *
LOCc
(
ja
+
n
-1)
On entry, the
j
-th column
of the matrix stored in
a
must contain the vector that defines the elementary reflector
H
(
j
),
ja
≤
j
≤
ja
+
k
-1
, as returned by
p?geqrf
 in the
k
 columns of its
distributed matrix
 argument
A
(
ia
:*,
ja
:
ja
+
k
-1)
.
ia
(global)
The row index in the global matrix
A
 indicating the first row of sub(
A
).
ja
(global)
The column index in the global matrix
A
 indicating the first column of sub(
A
).
desca
(global and local) array of size
dlen_
.
The array descriptor for the distributed matrix
A
.
tau
(local)
Array of size
LOCc
(
ja
+
k
-1).
tau
[
j
]
 contains the scalar factor of the elementary reflector
H
(
j
+1),
j
 = 0, 1, ...,
LOCc
(
ja
+k-1)
-1
, as returned by
p?geqrf
. This array is tied to the distributed matrix
A
.
work
(local)
Workspace array of size
lwork
.
lwork
(local or global)
The size of the array
work
.
lwork
 is local input and must be at least
lwork
≥
mpa
0 + max(1,
nqa
0)
,
where
iroffa
 = mod(
ia
-1,
mb_a
 ,
icoffa
 = mod(
ja
-1,
nb_a
)
,
iarow
 =
indxg2p
(
ia
,
mb_a
,
myrow
,
rsrc
_a,
nprow
)
,
iacol
 =
indxg2p
(
ja
,
nb_a
,
mycol
,
csrc_a
,
npcol
)
,
mpa
0 =
numroc
(
m
+
iroffa
,
mb_a
,
myrow
,
iarow
,
nprow
)
,
nqa
0 =
numroc
(
n
+
icoffa
,
nb_a
,
mycol
,
iacol
,
npcol
)
.
indxg2p
 and
numroc
 are ScaLAPACK tool functions;
myrow
,
mycol
,
nprow
, and
npcol
 can be determined by calling the
function
blacs_gridinfo
.
If
lwork
 = -1
, then
lwork
 is global input and a workspace query is assumed; the
function
only calculates the minimum and optimal size for all work arrays. Each of these values is returned in the first entry of the corresponding work array, and no error message is issued by
pxerbla
.
Output Parameters
a
On exit, this array contains the local pieces of the
m
-by-
n
 distributed matrix
Q
.
work
On exit,
work
[0]
 returns the minimal and optimal
lwork
.
info
(local).
= 0
: successful exit
< 0
: if the
i
-th argument is an array and the
j
-th entry
, indexed
j
-1,
 had an illegal value,
then
info
 = - (
i
*100 +
j
),
if the
i
-th argument is a scalar and had an illegal value,
then
info
 = -
i
.

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.