Pfthb

Let's say I have two arrays

A = 1, 2, 3

and

B = 10,20,30,40,50

I want to generate a new array which would have a size of

sizeof(A) * sizeof(B)

I want to replicate B sizeof(A) times, and on each repetition i, the resultant array should have A[i] added to it. So the result would be something like

11,21,31,41,51,12,22,32,42,52,13,23,33,43,53

This task can be interpreted as a 2-dimensional problem where the output array can be treated as a matrix of dimensions sizeof(A) times sizeof(B). In this way, we can use 2D CUDA indexing to achieve the desired functionality. A sample CUDA C++ code of this 2D implementation is shown below:

#include <iostream>
#include <cuda_runtime.h>
#include <cassert>

using namespace std;

__global__ void kernel_replicate(int* a, int* b, int* c, int alen, int blen, int clen)

 const int ai = blockIdx.x * blockDim.x + threadIdx.x;
 const int bi = blockIdx.y * blockDim.y + threadIdx.y;

 if(ai<alen && bi<blen)
 
 const int ci = ai * blen + bi;
 c[ci] = a[ai] + b[bi];
 



void replicate_device(int* a, int* b, int* c, int alen, int blen, int clen)

 dim3 block(16,16);
 dim3 grid;
 grid.x = (alen + block.x - 1) / block.x;
 grid.y = (blen + block.y - 1) / block.y;

 kernel_replicate<<<grid, block>>>(a,b,c,alen,blen,clen);

 assert(cudaSuccess == cudaDeviceSynchronize());



void replicate(int* a, int* b, int* c, int alen, int blen, int clen)

 int *ad, *bd, *cd;

 size_t abytes = alen * sizeof(int);
 size_t bbytes = blen * sizeof(int);
 size_t cbytes = clen * sizeof(int);

 cudaMalloc(&ad, abytes);
 cudaMalloc(&bd, bbytes);
 cudaMalloc(&cd, cbytes);

 cudaMemcpy(ad,a, abytes, cudaMemcpyHostToDevice);
 cudaMemcpy(bd,b, bbytes, cudaMemcpyHostToDevice);

 replicate_device(ad,bd,cd, alen,blen,clen);

 cudaMemcpy(c,cd, cbytes, cudaMemcpyDeviceToHost);


 cudaFree(ad);
 cudaFree(bd);
 cudaFree(cd);



int main()

 const int alen = 3;
 const int blen = 5;
 const int clen = alen * blen;

 int A[alen] = 1,2,3;
 int B[blen] = 10,20,30,40,50;
 int C[clen] = 0;

 replicate(A,B,C,alen, blen, clen);

 for(int i=0; i<alen; i++)
 
 cout<<A[i]<<" ";
 
 cout<<endl;

 for(int i=0; i<blen; i++)
 
 cout<<B[i]<<" ";
 
 cout<<endl;

 for(int i=0; i<clen; i++)
 
 cout<<C[i]<<" ";
 
 cout<<endl;


 return 0;