select

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select#

Selects value from a tensor based on a 1D index mapping. The 1D index mapping works for any rank tensor. Usually the mapping is provided by find_idx, but any source with the same mapping will work.

template<typename T, typename IdxType>
auto __MATX_INLINE__ matx::select(const T &t, IdxType idx)#

Helper function to select values from a predicate operator.

select() is used to index from a source operator using indices stored in another operator. This is commonly used with the find_idx executor which returns the indices of values meeting a selection criteria.

Template Parameters:

  • T – Input type

  • IdxType – Operator with indices

Parameters:

  • t – Input operator

  • idx – Index tensor

Returns:

Value in t from each location in idx

Examples#

(mtie(t1o_idx, num_found) = find_idx(t1, GT{thresh})).run(exec);

// Since we use the output on the host in select() we need to synchronize first
exec.sync();

auto t1o_slice = slice(t1o, {0}, {num_found()});
auto t1o_idx_slice = slice(t1o_idx, {0}, {num_found()});
(t1o_slice = select(t1o_slice, t1o_idx_slice)).run(exec);

// Compare to simply finding the values
(mtie(t1o_2, num_found2) = find(t1, GT{thresh})).run(exec);
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