Developer Reference

Contents

cblas_?gbmv

Computes a matrix-vector product with a general band matrix.

Syntax

void
cblas_sgbmv
(
const
CBLAS_LAYOUT
Layout
,
const
CBLAS_TRANSPOSE
trans
,
const
MKL_INT
m
,
const
MKL_INT
n
,
const
MKL_INT
kl
,
const
MKL_INT
ku
,
const
float
alpha
,
const
float
*a
,
const
MKL_INT
lda
,
const
float
*x
,
const
MKL_INT
incx
,
const
float
beta
,
float
*y
,
const
MKL_INT
incy
);
void
cblas_dgbmv
(
const
CBLAS_LAYOUT
Layout
,
const
CBLAS_TRANSPOSE
trans
,
const
MKL_INT
m
,
const
MKL_INT
n
,
const
MKL_INT
kl
,
const
MKL_INT
ku
,
const
double
alpha
,
const
double
*a
,
const
MKL_INT
lda
,
const
double
*x
,
const
MKL_INT
incx
,
const
double
beta
,
double
*y
,
const
MKL_INT
incy
);
void
cblas_cgbmv
(
const
CBLAS_LAYOUT
Layout
,
const
CBLAS_TRANSPOSE
trans
,
const
MKL_INT
m
,
const
MKL_INT
n
,
const
MKL_INT
kl
,
const
MKL_INT
ku
,
const
void
*alpha
,
const
void
*a
,
const
MKL_INT
lda
,
const
void
*x
,
const
MKL_INT
incx
,
const
void
*beta
,
void
*y
,
const
MKL_INT
incy
);
void
cblas_zgbmv
(
const
CBLAS_LAYOUT
Layout
,
const
CBLAS_TRANSPOSE
trans
,
const
MKL_INT
m
,
const
MKL_INT
n
,
const
MKL_INT
kl
,
const
MKL_INT
ku
,
const
void
*alpha
,
const
void
*a
,
const
MKL_INT
lda
,
const
void
*x
,
const
MKL_INT
incx
,
const
void
*beta
,
void
*y
,
const
MKL_INT
incy
);
Include Files
  • mkl.h
Description
The
?gbmv
routines perform a matrix-vector operation defined as
y
:=
alpha
*
A
*
x
+
beta
*
y
,
or
y
:=
alpha
*
A
'*
x
+
beta
*
y
,
or
y
:=
alpha
*conjg(
A
')*
x
+
beta
*
y
,
where:
alpha
and
beta
are scalars,
x
and
y
are vectors,
A
is an
m
-by-
n
band matrix, with
kl
sub-diagonals and
ku
super-diagonals.
Input Parameters
Layout
Specifies whether two-dimensional array storage is row-major (
CblasRowMajor
) or column-major (
CblasColMajor
).
trans
Specifies the operation:
If
trans
=
CblasNoTrans
, then
y
:=
alpha
*
A
*
x
+
beta
*
y
If
trans
=
CblasTrans
, then
y
:=
alpha
*
A
'*
x
+
beta
*
y
If
trans
=
CblasConjTrans
, then
y
:=
alpha
*conjg(
A
')*
x
+
beta
*
y
m
Specifies the number of rows of the matrix
A
.
The value of
m
must be at least zero.
n
Specifies the number of columns of the matrix
A
.
The value of
n
must be at least zero.
kl
Specifies the number of sub-diagonals of the matrix
A
.
The value of
kl
must satisfy
0
kl
.
ku
Specifies the number of super-diagonals of the matrix
A
.
The value of
ku
must satisfy
0
ku
.
alpha
Specifies the scalar
alpha
.
a
Array, size
lda
*
n
.
Layout
=
CblasColMajor
:
Before entry, the leading
(
kl
+
ku
+ 1)
by
n
part of the array
a
must contain the matrix of coefficients. This matrix must be supplied column-by-column, with the leading diagonal of the matrix in row
(
ku
)
of the array, the first super-diagonal starting at position
1
in row
(
ku
- 1)
, the first sub-diagonal starting at position
0
in row
(
ku
+
1
)
, and so on. Elements in the array
a
that do not correspond to elements in the band matrix (such as the top left
ku
by
ku
triangle) are not referenced.
The following program segment transfers a band matrix from conventional full matrix storage (
matrix
, with leading dimension
ldm
) to band storage (
a
, with leading dimension
lda
):
for (j = 0; j < n; j++) { k = ku - j; for (i = max(0, j-ku); i < min(m, j+kl+1); i++) { a[(k+i) + j*lda] = matrix[i + j*ldm]; } }
Layout
=
CblasRowMajor
: Before entry, the leading
(
kl
+
ku
+ 1)
by
m
part of the array
a
must contain the matrix of coefficients. This matrix must be supplied row-by-row, with the leading diagonal of the matrix in column
(
kl
)
of the array, the first super-diagonal starting at position 0 in column
(
kl
+ 1)
, the first sub-diagonal starting at position 1 in row
(
kl
- 1)
, and so on. Elements in the array
a
that do not correspond to elements in the band matrix (such as the top left
kl
by
kl
triangle) are not referenced.
The following program segment transfers a band matrix from row-major full matrix storage (
matrix
, with leading dimension
ldm
) to band storage (
a
, with leading dimension
lda
):
for (i = 0; i < m; i++) { k = kl - i; for (j = max(0, i-kl); j < min(n, i+ku+1); j++) { a[(k+j) + i*lda] = matrix[j + i*ldm]; } }
lda
Specifies the leading dimension of
a
as declared in the calling (sub)program. The value of
lda
must be at least
(
kl
+
ku
+ 1)
.
x
Array, size at least
(1 + (
n
- 1)*abs(
incx
))
when
trans
=
CblasNoTrans
, and at least
(1 + (
m
- 1)*abs(
incx
))
otherwise. Before entry, the array
x
must contain the vector
x
.
incx
Specifies the increment for the elements of
x
.
incx
must not be zero.
beta
Specifies the scalar beta. When
beta
is equal to zero, then
y
need not be set on input.
y
Array, size at least
(1 +(
m
- 1)*abs(
incy
))
when
trans
=
CblasNoTrans
and at least
(1 +(
n
- 1)*abs(
incy
))
otherwise. Before entry, the incremented array
y
must contain the vector
y
.
incy
Specifies the increment for the elements of
y
.
The value of
incy
must not be zero.
Output Parameters
y
Buffer holding the updated vector
y
.

Product and Performance Information

1

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804