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> |
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 vectorx.
- x
- The buffer that holds the input vectorx. Size of the buffer must be at least (1 + (n- 1)*abs(incx)). See Matrix Storage for more details.
- incx
- The stride of vectorx.
Output Parameters
- result
- The buffer where the zero-based indexiof 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 vectorx.
- x
- The pointer to input vectorx. Size of the array holding input vectorxmust be at least (1 + (n- 1)*abs(incx)). See Matrix Storage for more details.
- incx
- The stride of vectorx.
- 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 indexiof the maximal element is stored.
Return Values
Output event to wait on to ensure computation is complete.