thrust

◆ gather() [1/2]

template<typename DerivedPolicy , typename InputIterator , typename RandomAccessIterator , typename OutputIterator >
__host__ __device__ OutputIterator thrust::gather ( const thrust::detail::execution_policy_base< DerivedPolicy > &  exec,
InputIterator  map_first,
InputIterator  map_last,
RandomAccessIterator  input_first,
OutputIterator  result 
)

gather copies elements from a source array into a destination range according to a map. For each input iterator i in the range [map_first, map_last), the value input_first[*i] is assigned to *(result + (i - map_first)). RandomAccessIterator must permit random access.

The algorithm's execution is parallelized as determined by exec.

Parameters
execThe execution policy to use for parallelization.
map_firstBeginning of the range of gather locations.
map_lastEnd of the range of gather locations.
input_firstBeginning of the source range.
resultBeginning of the destination range.
Template Parameters
DerivedPolicyThe name of the derived execution policy.
InputIteratormust be a model of Input Iterator and InputIterator's value_type must be convertible to RandomAccessIterator's difference_type.
RandomAccessIteratormust be a model of Random Access Iterator and RandomAccessIterator's value_type must be convertible to OutputIterator's value_type.
OutputIteratormust be a model of Output Iterator.
Precondition
The range [map_first, map_last) shall not overlap the range [result, result + (map_last - map_first)).
Remarks
gather is the inverse of thrust::scatter.

The following code snippet demonstrates how to use gather to reorder a range using the thrust::device execution policy for parallelization:

#include <thrust/gather.h>
...
// mark even indices with a 1; odd indices with a 0
int values[10] = {1, 0, 1, 0, 1, 0, 1, 0, 1, 0};
thrust::device_vector<int> d_values(values, values + 10);
// gather all even indices into the first half of the range
// and odd indices to the last half of the range
int map[10] = {0, 2, 4, 6, 8, 1, 3, 5, 7, 9};
thrust::device_vector<int> d_map(map, map + 10);
d_map.begin(), d_map.end(),
d_values.begin(),
d_output.begin());
// d_output is now {1, 1, 1, 1, 1, 0, 0, 0, 0, 0}