cuda - removing elements from an device_vector -

thrust::device_vector values

thrust::device_vector keys;

after initialization, keys contains elements equal -1. wanted delete elements in keys , in same position of values.

but not know how deal parallel?

there many ways this. 1 possible way:

1. use stencil version of thrust::remove_if (documentation), keys stencil, removing elements in values corresponding key -1. need create functor predicate test.
2. use thrust::remove (documentation) on keys remove values -1

here's example:

#include <iostream> #include <thrust/device_vector.h> #include <thrust/copy.h> #include <thrust/remove.h> #include <thrust/sequence.h>  #define n 12 typedef thrust::device_vector<int>::iterator dintiter;  struct is_minus_one {   __host__ __device__   bool operator()(const int x)   {     return (x == -1);   } };  int main(){    thrust::device_vector<int> keys(n);   thrust::device_vector<int> values(n);    thrust::sequence(keys.begin(), keys.end());   thrust::sequence(values.begin(), values.end());    keys[3] = -1;   keys[9] = -1;    dintiter nve = thrust::remove_if(values.begin(), values.end(), keys.begin(), is_minus_one());   dintiter nke = thrust::remove(keys.begin(), keys.end(), -1);    std::cout << "results  values:" << std::endl;   thrust::copy(values.begin(), nve, std::ostream_iterator<int>( std::cout, " "));   std::cout << std::endl << "results keys:" << std::endl;   thrust::copy(keys.begin(), nke, std::ostream_iterator<int>( std::cout, " "));   std::cout << std::endl;    return 0; }