Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

Contents

cblas_?spr2

Computes a rank-2 update of a symmetric packed matrix.

Syntax

void
cblas_sspr2
(
const
CBLAS_LAYOUT
Layout
,
const
CBLAS_UPLO
uplo
,
const
MKL_INT
n
,
const
float
alpha
,
const
float
*x
,
const
MKL_INT
incx
,
const
float
*y
,
const
MKL_INT
incy
,
float
*ap
);
void
cblas_dspr2
(
const
CBLAS_LAYOUT
Layout
,
const
CBLAS_UPLO
uplo
,
const
MKL_INT
n
,
const
double
alpha
,
const
double
*x
,
const
MKL_INT
incx
,
const
double
*y
,
const
MKL_INT
incy
,
double
*ap
);
Include Files
  • mkl.h
Description
The
?spr2
 routines perform a matrix-vector operation defined as 
A:= alpha*x*y'+ alpha*y*x' + A,
where:
alpha
 is a scalar,
x
 and
y
 are
n
-element vectors,
A
 is an
n
-by-
n
 symmetric matrix, supplied in packed form.
Input Parameters
Layout
Specifies whether two-dimensional array storage is row-major (
CblasRowMajor
) or column-major (
CblasColMajor
).
uplo
Specifies whether the upper or lower triangular part of the matrix
A
 is supplied in the packed array
ap
.
If
uplo
 =
CblasUpper
, then the upper triangular part of the matrix
A
 is supplied in the packed array
ap
 .
If
uplo
 =
CblasLower
, then the low triangular part of the matrix
A
 is supplied in the packed array
ap
 .
n
Specifies the order of the matrix
A
. The value of
n
 must be at least zero.
alpha
Specifies the scalar
alpha
.
x
Array, size at least
(1 + (
n
 - 1)*abs(
incx
))
. Before entry, the incremented array
x
 must contain the
n
-element vector
x
.
incx
Specifies the increment for the elements of
x
.
The value of
incx
 must not be zero.
y
Array, size at least
(1 + (
n
 - 1)*abs(
incy
))
. Before entry, the incremented array
y
 must contain the
n
-element vector
y
.
incy
Specifies the increment for the elements of
y
. The value of
incy
 must not be zero.
ap
For
Layout
 =
CblasColMajor
:
Before entry with
uplo
 =
CblasUpper
, the array
ap
 must contain the upper triangular part of the symmetric matrix packed sequentially, column-by-column, so that
ap
[0]
 contains
A
1, 1
,
ap
[1]
 and
ap
[2]
 contain
A
1, 2
 and
A
2, 2
 respectively, and so on.
Before entry with
uplo
 =
CblasLower
, the array
ap
 must contain the lower triangular part of the symmetric matrix packed sequentially, column-by-column, so that
ap
[0]
 contains
A
1, 1
,
ap
[1]
 and
ap
[2]
 contain
A
2, 1
 and
A
3, 1
 respectively, and so on.
For
Layout
 =
CblasRowMajor
:
Before entry with
uplo
 =
CblasUpper
, the array
ap
 must contain the upper triangular part of the symmetric matrix packed sequentially, row-by-row,
ap
[0]
 contains
A
1, 1
,
ap
[1]
 and
ap
[2]
 contain
A
1, 2
 and
A
1, 3
 respectively, and so on.
Before entry with
uplo
 =
CblasLower
, the array
ap
 must contain the lower triangular part of the symmetric matrix packed sequentially, row-by-row, so that
ap
[0]
 contains
A
1, 1
,
ap
[1]
 and
ap
[2]
 contain
A
2, 1
 and
A
2, 2
 respectively, and so on.
Output Parameters
ap
With
uplo
 =
CblasUpper
, overwritten by the upper triangular part of the updated matrix.
With
uplo
 =
CblasLower
, overwritten by the lower triangular part of the updated matrix.

Product and Performance Information

1

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