◆ for_each_n() [2/2]

template<typename InputIterator , typename Size , typename UnaryFunction >
InputIterator thrust::for_each_n ( InputIterator  first,
Size  n,
UnaryFunction  f 

for_each_n applies the function object f to each element in the range [first, first + n); f's return value, if any, is ignored. Unlike the C++ Standard Template Library function std::for_each, this version offers no guarantee on order of execution.

firstThe beginning of the sequence.
nThe size of the input sequence.
fThe function object to apply to the range [first, first + n).
first + n
Template Parameters
InputIteratoris a model of Input Iterator, and InputIterator's value_type is convertible to UnaryFunction's argument_type.
Sizeis an integral type.
UnaryFunctionis a model of Unary Function, and UnaryFunction does not apply any non-constant operation through its argument.

The following code snippet demonstrates how to use for_each_n to print the elements of a device_vector.

#include <stdio.h>
struct printf_functor
__host__ __device__
void operator()(int x)
// note that using printf in a __device__ function requires
// code compiled for a GPU with compute capability 2.0 or
// higher (nvcc --arch=sm_20)
printf("%d\n", x);
thrust::device_vector<int> d_vec(3);
d_vec[0] = 0; d_vec[1] = 1; d_vec[2] = 2;
thrust::for_each_n(d_vec.begin(), d_vec.size(), printf_functor());
// 0 1 2 is printed to standard output in some unspecified order
See also