iamax

oneMKL - Data Parallel C++ Developer Reference

Download PDF

ID 772045

Date 3/31/2021

Version

Public

A newer version of this document is available. Customers should click here to go to the newest version.

Visible to Intel only — GUID: GUID-8EA7FC97-CE4E-453E-9AC8-D7004680ADC7

View Details

iamax

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

Description

The iamax routines return an index i such 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).

iamax supports the following precisions:

T
`float`
`double`
`std::complex<float>`
`std:complex<double>`

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.

iamax (Buffer Version)

Syntax

namespace oneapi::mkl::blas::column_major {
    void iamax(sycl::queue &queue,
               std::int64_t n,
               sycl::buffer<T, 1> &x,
               std::int64_t incx,
               sycl::buffer<std::int64_t, 1> &result)
}

namespace oneapi::mkl::blas::row_major {
    void iamax(sycl::queue &queue,
               std::int64_t n,
               sycl::buffer<T, 1> &x,
               std::int64_t incx,
               sycl::buffer<std::int64_t, 1> &result)
}

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. Size of the buffer must be at least (1 + (n - 1)*abs(incx)). See Matrix 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.

Examples

An example of how to use iamax can be found in the oneMKL installation directory, under:

examples/dpcpp/blas/source/iamax.cpp

iamax (USM Version)

Syntax

namespace oneapi::mkl::blas::column_major {
    sycl::event iamax(sycl::queue &queue,
                      std::int64_t n,
                      const T *x,
                      std::int64_t incx,
                      std::int64_t *result,
                      const std::vector<sycl::event> &dependencies = {})
}

namespace oneapi::mkl::blas::row_major {
    sycl::event iamax(sycl::queue &queue,
                      std::int64_t n,
                      const T *x,
                      std::int64_t incx,
                      std::int64_t *result,
                      const std::vector<sycl::event> &dependencies = {})
}

Input Parameters

queue: The queue where the routine should be executed.
n: The number of elements in vector x.
x: The pointer to input vector x. Size of the array holding input vector x must be at least (1 + (n - 1)*abs(incx)). See Matrix Storage for more details.
incx: The stride of vector x.
dependencies: List of events to wait for before starting computation, if any. If omitted, defaults to no dependencies.

Output Parameters

result: The pointer to where the zero-based index i of the maximal element is stored.

Return Values

Output event to wait on to ensure computation is complete.

Select Your Language

Using Intel.com Search

Quick Links

Recent Searches

Advanced Search

Only search in

oneMKL - Data Parallel C++ Developer Reference

iamax

Description

iamax (Buffer Version)

Examples

iamax (USM Version)