Detect values greater than threshold in an array and store result in a binary(1/0) array using thrust












0















Given an input array and a threshold, I need to create an output binary array with 1's for values greater than threshold and 0's for values less than threshold. I need to use thrust.



My attempt as below solves the problem but looks very clumsy. How to do it in a single step. My target is to do it in minimum computation time. 



#include <thrust/replace.h>

#include <thrust/execution_policy.h>

#include <thrust/fill.h>

#include <thrust/device_vector.h>



int main(int argc, char * argv)

{

int threshold=1;

thrust::device_vector<int> S(6);

S[0] = 1;

S[1] = 2;

S[2] = 3;

S[3] = 4;

S[4] = 5;

S[5] = 6;



// fill vector with zeros

thrust::device_vector<int> A(6);

thrust::fill(thrust::device, A.begin(), A.end(), 0);



// detect indices with values greater than zero

thrust::device_vector<int> indices(6);

thrust::device_vector<int>::iterator end = thrust::copy_if(thrust::make_counting_iterator(0),thrust::make_counting_iterator(6),S.begin(),indices.begin(),                                                              thrust::placeholders::_1 > threshold);

int size = end-indices.begin();

indices.resize(size);



// use permutation iterator along with indices above to change to ones



thrust::replace(thrust::device,thrust::make_permutation_iterator(A.begin(), indices.begin()), thrust::make_permutation_iterator(A.begin(), indices.end()), 0, 1);



for (int i=0;i<6;i++)

{

std::cout << "A["<<i<<"]=" << A[i] << std::endl;

}



return 0;

}


The indices detection part is taken from this Stackoverflow question






arrays cuda thrust threshold







share|improve this question



























    0















    Given an input array and a threshold, I need to create an output binary array with 1's for values greater than threshold and 0's for values less than threshold. I need to use thrust.



    My attempt as below solves the problem but looks very clumsy. How to do it in a single step. My target is to do it in minimum computation time. 



    #include <thrust/replace.h>
    
#include <thrust/execution_policy.h>
    
#include <thrust/fill.h>
    
#include <thrust/device_vector.h>
    

    
int main(int argc, char * argv)
    
{
    
int threshold=1;
    
thrust::device_vector<int> S(6);
    
S[0] = 1;
    
S[1] = 2;
    
S[2] = 3;
    
S[3] = 4;
    
S[4] = 5;
    
S[5] = 6;
    

    
// fill vector with zeros
    
thrust::device_vector<int> A(6);
    
thrust::fill(thrust::device, A.begin(), A.end(), 0);
    

    
// detect indices with values greater than zero
    
thrust::device_vector<int> indices(6);
    
thrust::device_vector<int>::iterator end = thrust::copy_if(thrust::make_counting_iterator(0),thrust::make_counting_iterator(6),S.begin(),indices.begin(),                                                              thrust::placeholders::_1 > threshold);
    
int size = end-indices.begin();
    
indices.resize(size);
    

    
// use permutation iterator along with indices above to change to ones
    

    
thrust::replace(thrust::device,thrust::make_permutation_iterator(A.begin(), indices.begin()), thrust::make_permutation_iterator(A.begin(), indices.end()), 0, 1);
    

    
for (int i=0;i<6;i++)
    
{
    
std::cout << "A["<<i<<"]=" << A[i] << std::endl;
    
}
    

    
return 0;
    
}


    The indices detection part is taken from this Stackoverflow question






    arrays cuda thrust threshold







    share|improve this question

























      0












      0








      0








      Given an input array and a threshold, I need to create an output binary array with 1's for values greater than threshold and 0's for values less than threshold. I need to use thrust.



      My attempt as below solves the problem but looks very clumsy. How to do it in a single step. My target is to do it in minimum computation time. 



      #include <thrust/replace.h>
      
#include <thrust/execution_policy.h>
      
#include <thrust/fill.h>
      
#include <thrust/device_vector.h>
      

      
int main(int argc, char * argv)
      
{
      
int threshold=1;
      
thrust::device_vector<int> S(6);
      
S[0] = 1;
      
S[1] = 2;
      
S[2] = 3;
      
S[3] = 4;
      
S[4] = 5;
      
S[5] = 6;
      

      
// fill vector with zeros
      
thrust::device_vector<int> A(6);
      
thrust::fill(thrust::device, A.begin(), A.end(), 0);
      

      
// detect indices with values greater than zero
      
thrust::device_vector<int> indices(6);
      
thrust::device_vector<int>::iterator end = thrust::copy_if(thrust::make_counting_iterator(0),thrust::make_counting_iterator(6),S.begin(),indices.begin(),                                                              thrust::placeholders::_1 > threshold);
      
int size = end-indices.begin();
      
indices.resize(size);
      

      
// use permutation iterator along with indices above to change to ones
      

      
thrust::replace(thrust::device,thrust::make_permutation_iterator(A.begin(), indices.begin()), thrust::make_permutation_iterator(A.begin(), indices.end()), 0, 1);
      

      
for (int i=0;i<6;i++)
      
{
      
std::cout << "A["<<i<<"]=" << A[i] << std::endl;
      
}
      

      
return 0;
      
}


      The indices detection part is taken from this Stackoverflow question






      arrays cuda thrust threshold







      share|improve this question














      Given an input array and a threshold, I need to create an output binary array with 1's for values greater than threshold and 0's for values less than threshold. I need to use thrust.



      My attempt as below solves the problem but looks very clumsy. How to do it in a single step. My target is to do it in minimum computation time. 



      #include <thrust/replace.h>
      
#include <thrust/execution_policy.h>
      
#include <thrust/fill.h>
      
#include <thrust/device_vector.h>
      

      
int main(int argc, char * argv)
      
{
      
int threshold=1;
      
thrust::device_vector<int> S(6);
      
S[0] = 1;
      
S[1] = 2;
      
S[2] = 3;
      
S[3] = 4;
      
S[4] = 5;
      
S[5] = 6;
      

      
// fill vector with zeros
      
thrust::device_vector<int> A(6);
      
thrust::fill(thrust::device, A.begin(), A.end(), 0);
      

      
// detect indices with values greater than zero
      
thrust::device_vector<int> indices(6);
      
thrust::device_vector<int>::iterator end = thrust::copy_if(thrust::make_counting_iterator(0),thrust::make_counting_iterator(6),S.begin(),indices.begin(),                                                              thrust::placeholders::_1 > threshold);
      
int size = end-indices.begin();
      
indices.resize(size);
      

      
// use permutation iterator along with indices above to change to ones
      

      
thrust::replace(thrust::device,thrust::make_permutation_iterator(A.begin(), indices.begin()), thrust::make_permutation_iterator(A.begin(), indices.end()), 0, 1);
      

      
for (int i=0;i<6;i++)
      
{
      
std::cout << "A["<<i<<"]=" << A[i] << std::endl;
      
}
      

      
return 0;
      
}


      The indices detection part is taken from this Stackoverflow question






      arrays cuda thrust threshold




      arrays cuda thrust threshold






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked Nov 20 '18 at 5:49









      user27665user27665

      331415




      331415
























          1 Answer
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          The required functionality can be achieved with a single call to thrust::transform with a custom comparison functor. Here is an example of the said approach.



          #include <thrust/execution_policy.h>
          
#include <thrust/device_vector.h>
          
#include <thrust/transform.h>    
          

          
template<class T>
          
struct thresher
          
{
          
    T _thresh;
          
    thresher(T thresh) : _thresh(thresh) { }
          

          
    __host__ __device__ int operator()(T &x) const
          
    {
          
        return int(x > _thresh);
          
    }
          
};
          

          
int main(int argc, char * argv)
          
{
          
    int threshold = 1;
          
    thrust::device_vector<int> S(6);
          
    S[0] = 1;
          
    S[1] = 2;
          
    S[2] = 3;
          
    S[3] = 4;
          
    S[4] = 5;
          
    S[5] = 6;
          

          
    thrust::device_vector<int> A(6);
          
    thrust::transform(S.begin(), S.end(), A.begin(), thresher<int>(threshold));
          

          
    for (int i=0;i<6;i++)
          
    {
          
        std::cout << "A["<<i<<"]=" << A[i] << std::endl;
          
    }
          

          
    return 0;
          
}





          share|improve this answer























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            1 Answer
            1






            active

            oldest

            votes








            1 Answer
            1






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            1














            The required functionality can be achieved with a single call to thrust::transform with a custom comparison functor. Here is an example of the said approach.



            #include <thrust/execution_policy.h>
            
#include <thrust/device_vector.h>
            
#include <thrust/transform.h>    
            

            
template<class T>
            
struct thresher
            
{
            
    T _thresh;
            
    thresher(T thresh) : _thresh(thresh) { }
            

            
    __host__ __device__ int operator()(T &x) const
            
    {
            
        return int(x > _thresh);
            
    }
            
};
            

            
int main(int argc, char * argv)
            
{
            
    int threshold = 1;
            
    thrust::device_vector<int> S(6);
            
    S[0] = 1;
            
    S[1] = 2;
            
    S[2] = 3;
            
    S[3] = 4;
            
    S[4] = 5;
            
    S[5] = 6;
            

            
    thrust::device_vector<int> A(6);
            
    thrust::transform(S.begin(), S.end(), A.begin(), thresher<int>(threshold));
            

            
    for (int i=0;i<6;i++)
            
    {
            
        std::cout << "A["<<i<<"]=" << A[i] << std::endl;
            
    }
            

            
    return 0;
            
}





            share|improve this answer




























              1














              The required functionality can be achieved with a single call to thrust::transform with a custom comparison functor. Here is an example of the said approach.



              #include <thrust/execution_policy.h>
              
#include <thrust/device_vector.h>
              
#include <thrust/transform.h>    
              

              
template<class T>
              
struct thresher
              
{
              
    T _thresh;
              
    thresher(T thresh) : _thresh(thresh) { }
              

              
    __host__ __device__ int operator()(T &x) const
              
    {
              
        return int(x > _thresh);
              
    }
              
};
              

              
int main(int argc, char * argv)
              
{
              
    int threshold = 1;
              
    thrust::device_vector<int> S(6);
              
    S[0] = 1;
              
    S[1] = 2;
              
    S[2] = 3;
              
    S[3] = 4;
              
    S[4] = 5;
              
    S[5] = 6;
              

              
    thrust::device_vector<int> A(6);
              
    thrust::transform(S.begin(), S.end(), A.begin(), thresher<int>(threshold));
              

              
    for (int i=0;i<6;i++)
              
    {
              
        std::cout << "A["<<i<<"]=" << A[i] << std::endl;
              
    }
              

              
    return 0;
              
}





              share|improve this answer


























                1












                1








                1







                The required functionality can be achieved with a single call to thrust::transform with a custom comparison functor. Here is an example of the said approach.



                #include <thrust/execution_policy.h>
                
#include <thrust/device_vector.h>
                
#include <thrust/transform.h>    
                

                
template<class T>
                
struct thresher
                
{
                
    T _thresh;
                
    thresher(T thresh) : _thresh(thresh) { }
                

                
    __host__ __device__ int operator()(T &x) const
                
    {
                
        return int(x > _thresh);
                
    }
                
};
                

                
int main(int argc, char * argv)
                
{
                
    int threshold = 1;
                
    thrust::device_vector<int> S(6);
                
    S[0] = 1;
                
    S[1] = 2;
                
    S[2] = 3;
                
    S[3] = 4;
                
    S[4] = 5;
                
    S[5] = 6;
                

                
    thrust::device_vector<int> A(6);
                
    thrust::transform(S.begin(), S.end(), A.begin(), thresher<int>(threshold));
                

                
    for (int i=0;i<6;i++)
                
    {
                
        std::cout << "A["<<i<<"]=" << A[i] << std::endl;
                
    }
                

                
    return 0;
                
}





                share|improve this answer













                The required functionality can be achieved with a single call to thrust::transform with a custom comparison functor. Here is an example of the said approach.



                #include <thrust/execution_policy.h>
                
#include <thrust/device_vector.h>
                
#include <thrust/transform.h>    
                

                
template<class T>
                
struct thresher
                
{
                
    T _thresh;
                
    thresher(T thresh) : _thresh(thresh) { }
                

                
    __host__ __device__ int operator()(T &x) const
                
    {
                
        return int(x > _thresh);
                
    }
                
};
                

                
int main(int argc, char * argv)
                
{
                
    int threshold = 1;
                
    thrust::device_vector<int> S(6);
                
    S[0] = 1;
                
    S[1] = 2;
                
    S[2] = 3;
                
    S[3] = 4;
                
    S[4] = 5;
                
    S[5] = 6;
                

                
    thrust::device_vector<int> A(6);
                
    thrust::transform(S.begin(), S.end(), A.begin(), thresher<int>(threshold));
                

                
    for (int i=0;i<6;i++)
                
    {
                
        std::cout << "A["<<i<<"]=" << A[i] << std::endl;
                
    }
                

                
    return 0;
                
}






                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered Nov 21 '18 at 6:26









                sgarizvisgarizvi

                12.3k84278




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