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).

The index is zero-based if base is set to oneapi::math::index_base::zero (default) or one-based if it is set to oneapi::math::index_base::one.

If either n or incx is not positive, the routine returns 0, regardless of the base of the index selected.

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 supports the following precisions.

T

float

double

std::complex<float>

std:complex<double>

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

iamax (Buffer Version)#

Syntax

namespace oneapi::math::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,
               oneapi::math::index_base base = oneapi::math::index_base::zero)
}

namespace oneapi::math::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,
               oneapi::math::index_base base = oneapi::math::index_base::zero)
}

Input Parameters

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 Storage for more details.
incx: The stride of vector x.
base: Indicates how the output value is indexed. If omitted, defaults to zero-based indexing.

Output Parameters

result: The buffer where the index i of the maximal element is stored.

Throws

This routine shall throw the following exceptions if the associated condition is detected. An implementation may throw additional implementation-specific exception(s) in case of error conditions not covered here.

oneapi::math::invalid_argument

oneapi::math::unsupported_device

oneapi::math::host_bad_alloc

oneapi::math::device_bad_alloc

oneapi::math::unimplemented

iamax (USM Version)#

Syntax

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

namespace oneapi::math::blas::row_major {
    sycl::event iamax(sycl::queue &queue,
                      std::int64_t n,
                      const T *x,
                      std::int64_t incx,
                      std::int64_t *result,
                      oneapi::math::index_base base = oneapi::math::index_base::zero,
                      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 the input vector x. The array holding the input vector x must be of size at least (1 + (n - 1)*abs(incx)). See Matrix Storage for more details.
incx: The stride of vector x.
base: Indicates how the output value is indexed. If omitted, defaults to zero-based indexing.
dependencies: List of events to wait for before starting computation, if any. If omitted, defaults to no dependencies.