thrust::scatter_if

Defined in thrust/scatter.h

template<typename DerivedPolicy, typename InputIterator1, typename InputIterator2, typename InputIterator3, typename RandomAccessIterator, typename Predicate> void thrust::scatter_if(const thrust::detail::execution_policy_base<DerivedPolicy> &exec, InputIterator1 first, InputIterator1 last, InputIterator2 map, InputIterator3 stencil, RandomAccessIterator output, Predicate pred)

scatter_if conditionally copies elements from a source range into an output array according to a map. For each iterator i in the range [first, last) such that pred(*(stencil + (i - first))) is true, the value *i is assigned to output[*(map + (i - first))]. The output iterator must permit random access. If the same index appears more than once in the range [map, map + (last - first)) the result is undefined.

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

#include <thrust/scatter.h>
#include <thrust/execution_policy.h>

struct is_even
{
  __host__ __device__
  bool operator()(int x)
  {
    return (x % 2) == 0;
  }
};

...

int V[8] = {10, 20, 30, 40, 50, 60, 70, 80};
int M[8] = {0, 5, 1, 6, 2, 7, 3, 4};
int S[8] = {2, 1, 2, 1, 2, 1, 2, 1};
int D[8] = {0, 0, 0, 0, 0, 0, 0, 0};

is_even pred;
thrust::scatter_if(thrust::host, V, V + 8, M, S, D, pred);

// D contains [10, 30, 50, 70, 0, 0, 0, 0];

Note

scatter_if is the inverse of thrust::gather_if.

Parameters

exec – The execution policy to use for parallelization.
first – Beginning of the sequence of values to scatter.
last – End of the sequence of values to scatter.
map – Beginning of the sequence of output indices.
stencil – Beginning of the sequence of predicate values.
output – Beginning of the destination range.
pred – Predicate to apply to the stencil values.

Template Parameters

DerivedPolicy – The name of the derived execution policy.
InputIterator1 – must be a model of Input Iterator and InputIterator1's value_type must be convertible to RandomAccessIterator's value_type.
InputIterator2 – must be a model of Input Iterator and InputIterator2's value_type must be convertible to RandomAccessIterator's difference_type.
InputIterator3 – must be a model of Input Iterator and InputIterator3's value_type must be convertible to Predicate's argument type.
RandomAccessIterator – must be a model of Random Access iterator.
Predicate – must be a model of Predicate.

Pre

The iterator result + i shall not refer to any element referenced by any iterator j in the range [first,last) for all iterators i in the range [map,map + (last - first)).

Pre

The iterator result + i shall not refer to any element referenced by any iterator j in the range [map,map + (last - first)) for all iterators i in the range [map,map + (last - first)).

Pre

The iterator result + i shall not refer to any element referenced by any iterator j in the range [stencil,stencil + (last - first)) for all iterators i in the range [map,map + (last - first)).

Pre

The expression result[*i] shall be valid for all iterators i in the range [map,map + (last - first)) for which the following condition holds: pred(*(stencil + i)) != false.