copy_if#

Overloads#

copy_if(exec, first, last, result, pred)#

template<typename DerivedPolicy, typename InputIterator, typename OutputIterator, typename Predicate>
OutputIterator thrust::copy_if(
const thrust::detail::execution_policy_base<DerivedPolicy> &exec,
InputIterator first,
InputIterator last,
OutputIterator result,
Predicate pred,
)#

This version of copy_if copies elements from the range [first,last) to a range beginning at result, except that any element which causes pred to be false is not copied. copy_if is stable, meaning that the relative order of elements that are copied is unchanged.

More precisely, for every integer n such that 0 <= n < last-first, copy_if performs the assignment *result = *(first+n) and result is advanced one position if pred(*(first+n)). Otherwise, no assignment occurs and result is not advanced.

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

The following code snippet demonstrates how to use copy_if to perform stream compaction to copy even numbers to an output range using the thrust::host parallelization policy:

#include <thrust/copy.h>
#include <thrust/execution_policy.h>
...
struct is_even
{
  __host__ __device__
  bool operator()(const int x)
  {
    return (x % 2) == 0;
  }
};
...
const int N = 6;
int V[N] = {-2, 0, -1, 0, 1, 2};
int result[4];

thrust::copy_if(thrust::host, V, V + N, result, is_even());

// V remains {-2, 0, -1, 0, 1, 2}
// result is now {-2, 0, 0, 2}

See also

remove_copy_if

Parameters:

  • exec – The execution policy to use for parallelization.

  • first – The beginning of the sequence from which to copy.

  • last – The end of the sequence from which to copy.

  • result – The beginning of the sequence into which to copy.

  • pred – The predicate to test on every value of the range [first, last).

Template Parameters:

  • DerivedPolicy – The name of the derived execution policy.

  • InputIterator – is a model of Input Iterator, and InputIterator's value_type is convertible to Predicate's argument type.

  • OutputIterator – is a model of Output Iterator.

  • Predicate – is a model of Predicate.

Returns:

result + n, where n is equal to the number of times pred evaluated to true in the range [first, last).

Pre:

The ranges [first, last) and [result, result + (last - first)) shall not overlap.

copy_if(first, last, result, pred)#

template<typename InputIterator, typename OutputIterator, typename Predicate>
OutputIterator thrust::copy_if(
InputIterator first,
InputIterator last,
OutputIterator result,
Predicate pred,
)#

This version of copy_if copies elements from the range [first,last) to a range beginning at result, except that any element which causes pred to false is not copied. copy_if is stable, meaning that the relative order of elements that are copied is unchanged.

More precisely, for every integer n such that 0 <= n < last-first, copy_if performs the assignment *result = *(first+n) and result is advanced one position if pred(*(first+n)). Otherwise, no assignment occurs and result is not advanced.

The following code snippet demonstrates how to use copy_if to perform stream compaction to copy even numbers to an output range.

#include <thrust/copy.h>
...
struct is_even
{
  __host__ __device__
  bool operator()(const int x)
  {
    return (x % 2) == 0;
  }
};
...
const int N = 6;
int V[N] = {-2, 0, -1, 0, 1, 2};
int result[4];

thrust::copy_if(V, V + N, result, is_even());

// V remains {-2, 0, -1, 0, 1, 2}
// result is now {-2, 0, 0, 2}

See also

remove_copy_if

Parameters:

  • first – The beginning of the sequence from which to copy.

  • last – The end of the sequence from which to copy.

  • result – The beginning of the sequence into which to copy.

  • pred – The predicate to test on every value of the range [first, last).

Template Parameters:

  • InputIterator – is a model of Input Iterator, and InputIterator's value_type is convertible to Predicate's argument type.

  • OutputIterator – is a model of Output Iterator.

  • Predicate – is a model of Predicate.

Returns:

result + n, where n is equal to the number of times pred evaluated to true in the range [first, last).

Pre:

The ranges [first, last) and [result, result + (last - first)) shall not overlap.

copy_if(exec, first, last, stencil, result, pred)#

template<typename DerivedPolicy, typename InputIterator1, typename InputIterator2, typename OutputIterator, typename Predicate>
OutputIterator thrust::copy_if(
const thrust::detail::execution_policy_base<DerivedPolicy> &exec,
InputIterator1 first,
InputIterator1 last,
InputIterator2 stencil,
OutputIterator result,
Predicate pred,
)#

This version of copy_if copies elements from the range [first,last) to a range beginning at result, except that any element whose corresponding stencil element causes pred to be false is not copied. copy_if is stable, meaning that the relative order of elements that are copied is unchanged.

More precisely, for every integer n such that 0 <= n < last-first, copy_if performs the assignment *result = *(first+n) and result is advanced one position if pred(*(stencil+n)). Otherwise, no assignment occurs and result is not advanced.

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

The following code snippet demonstrates how to use copy_if to perform stream compaction to copy numbers to an output range when corresponding stencil elements are even using the thrust::host execution policy:

#include <thrust/copy.h>
#include <thrust/execution_policy.h>
...
struct is_even
{
  __host__ __device__
  bool operator()(const int x)
  {
    return (x % 2) == 0;
  }
};
...
int N = 6;
int data[N]    = { 0, 1,  2, 3, 4, 5};
int stencil[N] = {-2, 0, -1, 0, 1, 2};
int result[4];

thrust::copy_if(thrust::host, data, data + N, stencil, result, is_even());

// data remains    = { 0, 1,  2, 3, 4, 5};
// stencil remains = {-2, 0, -1, 0, 1, 2};
// result is now     { 0, 1,  3, 5}

See also

remove_copy_if

Parameters:

  • exec – The execution policy to use for parallelization.

  • first – The beginning of the sequence from which to copy.

  • last – The end of the sequence from which to copy.

  • stencil – The beginning of the stencil sequence.

  • result – The beginning of the sequence into which to copy.

  • pred – The predicate to test on every value of the range [stencil, stencil + (last-first)).

Template Parameters:

  • DerivedPolicy – The name of the derived execution policy.

  • InputIterator1 – is a model of Input Iterator.

  • InputIterator2 – is a model of Input Iterator, and InputIterator2's value_type is convertible to Predicate's argument type.

  • OutputIterator – is a model of Output Iterator.

  • Predicate – is a model of Predicate.

Returns:

result + n, where n is equal to the number of times pred evaluated to true in the range [stencil, stencil + (last-first)).

Pre:

The ranges [first, last) and [result, result + (last - first)) shall not overlap.

Pre:

The ranges [stencil, stencil + (last - first)) and [result, result + (last - first)) shall not overlap.

copy_if(first, last, stencil, result, pred)#

template<typename InputIterator1, typename InputIterator2, typename OutputIterator, typename Predicate>
OutputIterator thrust::copy_if(
InputIterator1 first,
InputIterator1 last,
InputIterator2 stencil,
OutputIterator result,
Predicate pred,
)#

This version of copy_if copies elements from the range [first,last) to a range beginning at result, except that any element whose corresponding stencil element causes pred to be false is not copied. copy_if is stable, meaning that the relative order of elements that are copied is unchanged.

More precisely, for every integer n such that 0 <= n < last-first, copy_if performs the assignment *result = *(first+n) and result is advanced one position if pred(*(stencil+n)). Otherwise, no assignment occurs and result is not advanced.

The following code snippet demonstrates how to use copy_if to perform stream compaction to copy numbers to an output range when corresponding stencil elements are even:

#include <thrust/copy.h>
...
struct is_even
{
  __host__ __device__
  bool operator()(const int x)
  {
    return (x % 2) == 0;
  }
};
...
int N = 6;
int data[N]    = { 0, 1,  2, 3, 4, 5};
int stencil[N] = {-2, 0, -1, 0, 1, 2};
int result[4];

thrust::copy_if(data, data + N, stencil, result, is_even());

// data remains    = { 0, 1,  2, 3, 4, 5};
// stencil remains = {-2, 0, -1, 0, 1, 2};
// result is now     { 0, 1,  3, 5}

See also

remove_copy_if

Parameters:

  • first – The beginning of the sequence from which to copy.

  • last – The end of the sequence from which to copy.

  • stencil – The beginning of the stencil sequence.

  • result – The beginning of the sequence into which to copy.

  • pred – The predicate to test on every value of the range [stencil, stencil + (last-first)).

Template Parameters:

  • InputIterator1 – is a model of Input Iterator.

  • InputIterator2 – is a model of Input Iterator, and InputIterator2's value_type is convertible to Predicate's argument type.

  • OutputIterator – is a model of Output Iterator.

  • Predicate – is a model of Predicate.

Returns:

result + n, where n is equal to the number of times pred evaluated to true in the range [stencil, stencil + (last-first)).

Pre:

The ranges [first, last) and [result, result + (last - first)) shall not overlap.

Pre:

The ranges [stencil, stencil + (last - first)) and [result, result + (last - first)) shall not overlap.