iamax

Finds the index of the element with the largest absolute value in a vector.

Syntax

void iamax(queue &exec_queue, std::int64_t n, buffer<T, 1> &x, std::int64_t incx, buffer<std::int64_t, 1> &result)

iamax supports the following precisions and devices:

T

Devices Supported

float

Host, CPU, and GPU

double

Host, CPU, and GPU

std::complex<float>

Host, CPU, and GPU

std:complex<double>

Host, CPU, and GPU

Description

The iamax routines return an index isuch that x[i] has the maximum absolute value of all elements in vector x (real variants), or such that |Re(x[i])| + |Im(x[i])| is maximal (complex variants).

Note

The index is zero-based.

If either n or incx are not positive, the routine returns 0.

If more than one vector element is found with the same largest absolute value, the index of the first one encountered is returned.

If the vector contains NaN values, then the routine returns the index of the first NaN.

Input Parameters

exec_queue

The queue where the routine should be executed.

n

The number of elements in vector x.

x

The buffer that holds the input vector x. The buffer must be of size at least (1 + (n - 1)*abs(incx)). See Matrix and Vector Storage for more details.

incx

The stride of vector x.

Output Parameters

result

The buffer where the zero-based index i of the maximal element is stored.

Example

An example of how to use iamaxcan be found in the Intel® oneMKL installation directory, under:

examples/sycl/blas/iamax.cpp