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).
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
supports the following precisions.
T
float
double
std::complex<float>
std:complex<double>
Note
The index is zero-based.
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
- 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
.
Output Parameters
- result
The buffer where the zero-based index
i
of the maximal element is stored.
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,
T_res *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,
T_res *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 the input vector
x
. The array holding the input vectorx
must be of size 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.
Parent topic: BLAS Level 1 Routines