Developer Reference for Intel® oneAPI Math Kernel Library for C
?spmv
Computes a matrix-vector product with a symmetric packed matrix.
Syntax
void cblas_sspmv(const CBLAS_LAYOUT Layout, const CBLAS_UPLO uplo, const MKL_INT n,
const float alpha, const float *ap, const float *x, const MKL_INT incx,
const float beta, float *y, const MKL_INT incy);
void cblas_dspmv(const CBLAS_LAYOUT Layout, const CBLAS_UPLO uplo, const MKL_INT n,
const double alpha, const double *ap, const double *x, const MKL_INT incx,
const double beta, double *y, const MKL_INT incy);Include Files
mkl.h
Description
The ?spmv routines perform a matrix-vector operation defined as y := alpha * A * x + beta * y ,
where:
alpha and beta are scalars,
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
-
REAL for sspmv DOUBLE PRECISION for dspmv Specifies the scalar alpha .
- ap
-
REAL for sspmv DOUBLE PRECISION for dspmv Array, size at least ((n*(n + 1))/2) . 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 A1, 1 , ap[1] and ap[2] contain A1, 2 and A2, 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 A1, 1 , ap[1] and ap[2] contain A2, 1 and A3, 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 A1, 1 , ap[1] and ap[2] contain A1, 2 and A1, 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 A1, 1 , ap[1] and ap[2] contain A2, 1 and A2, 2 respectively, and so on.
- x
-
REAL for sspmv DOUBLE PRECISION for dspmv 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.
- beta
-
REAL for sspmv DOUBLE PRECISION for dspmv Specifies the scalar beta . When beta is supplied as zero, then y need not be set on input.
- y
-
REAL for sspmv DOUBLE PRECISION for dspmv 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.
Output Parameters
- y
-
Overwritten by the updated vector y .
BLAS 95 Interface Notes
There exist FORTRAN 77 and FORTRAN 95 interfaces for this routine. See the Intel® oneMKL Fortran Developer Reference for details.