cblas_?axpy

Developer Reference for Intel® oneAPI Math Kernel Library for C

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ID 766684

Date 6/30/2025

Version

Public

cblas_?axpy_batch

Computes a group of vector-scalar products added to a vector.

Syntax

void cblas_saxpy_batch (const MKL_INT *n_array, const float *alpha_array, const float **x_array, const MKL_INT *incx_array, float **y_array, const MKL_INT *incy_array, const MKL_INT group_count, const MKL_INT *group_size_array);

void cblas_daxpy_batch (const MKL_INT *n_array, const double *alpha_array, const double **x_array, const MKL_INT *incx_array, double **y_array, const MKL_INT *incy_array, const MKL_INT group_count, const MKL_INT *group_size_array);

void cblas_caxpy_batch (const MKL_INT *n_array, const void *alpha_array, const void **x_array, const MKL_INT *incx_array, void **y_array, const MKL_INT *incy_array, const MKL_INT group_count, const MKL_INT *group_size_array);

void cblas_zaxpy_batch (const MKL_INT *n_array, const void *alpha_array, const void **x_array, const MKL_INT *incx_array, void **y_array, const MKL_INT *incy_array, const MKL_INT group_count, const MKL_INT *group_size_array);

Description

The cblas_?axpy_batch routines perform a series of scalar-vector product added to a vector. They are similar to the cblas_?axpy routine counterparts, but the cblas_?axpy_batch routines perform vector operations with a group of vectors. The groups contain vectors with the same parameters.

The operation is defined as

idx = 0
for i = 0 … group_count – 1
    n, alpha, incx, incy and group_size at position i in n_array, alpha_array, incx_array, incy_array and group_size_array
    for j = 0 … group_size – 1
        x and y are vectors of size n at position idx in x_array and y_array
        y := alpha * x + y
        idx := idx + 1
    end for
end for

The number of entries in x_array, and y_array is total_batch_count = the sum of all of the group_size entries.

Input Parameters

n_array: Array of size group_count. For the group i, n_i = n_array[i] is the number of elements in vectors x and y.
alpha_array: Array of size group_count. For the group i, alpha_i = alpha_array[i] is the scalar alpha.
x_array: Array of size total_batch_count of pointers used to store x vectors. The array allocated for the x vectors of the group i must be of size at least (1 + (n_i – 1)*abs(incx_i)).
incx_array: Array of size group_count. For the group i, incx_i = incx_array[i] is the stride of vector x.
y_array: Array of size total_batch_count of pointers used to store y vectors. The array allocated for the y vectors of the group i must be of size at least (1 + (n_i – 1)*abs(incy_i)).
incy_array: Array of size group_count. For the group i, incy_i = incy_array[i] is the stride of vector y.
group_count: Number of groups. Must be at least 0.
group_size_array: Array of size group_count. The element group_size_array[i] is the number of vector in the group i. Each element in group_size_array must be at least 0.

Output Parameters

y_array: Array of pointers holding the total_batch_count updated vector y.

Parent topic: BLAS-Like Extensions

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