scalar add

#include <thrust/host_vector.h> #include <thrust/device_vector.h> #include <iostream> __global__ void add(int *a, int *b,int *c){c[blockIdx.x]=a[blockIdx.x]+b[blockIdx.x];}int main(void) { // H has storage for 4 integersint a,b,c;int *da,*db,*dc;int size=1*sizeof(int); //scalar;cudaMalloc((void**)&da,size);cudaMalloc((void**)&db,size);cudaMalloc((void**)&dc,size);a=2;b=7;cudaMemcpy(da,&a,size,cudaMemcpyHostToDevice);cudaMemcpy(db,&b,size,cudaMemcpyHostToDevice);add<<<1,1>>>(da,db,dc);cudaMemcpy(&c,dc,size,cudaMemcpyDeviceToHost );std::cout<<c<<std::endl;cudaFree(da);cudaFree(db);cudaFree(dc);std::cout<<"hell"; thrust::host_vector<int> H(4); // initialize individual elements H[0] = 14; H[1] = 20; H[2] = 38; H[3] = 46; // H.size() returns the size of vector H std::cout << "H has size " << H.size() << std::endl; // print contents of H for(int i = 0; i < H.size(); i++) std::cout << "H[" << i << "] = " << H[i] << std::endl; // resize H H.resize(2); std::cout << "H now has size " << H.size() << std::endl; // Copy host_vector H to device_vector D thrust::device_vector<int> D = H; // elements of D can be modified D[0] = 99; D[1] = 88; // print contents of D for(int i = 0; i < D.size(); i++) std::cout << "D[" << i << "] = " << D[i] << std::endl; // H and D are automatically deleted when the function returns return 0; }

block or thread

#include <thrust/host_vector.h> #include <thrust/device_vector.h> #include <iostream>  const int N=512;__global__ void add(int *a, int *b,int *c){c[blockIdx.x]=a[blockIdx.x]+b[blockIdx.x];      //c[threadIdx.x]=a[threadIdx.x]+b[threadIdx.x];}int main(void) { // H has storage for 4 integersint *a,*b,*c;int *da,*db,*dc;int size=N*sizeof(int); //scalar;cudaMalloc((void**)&da,size);cudaMalloc((void**)&db,size);cudaMalloc((void**)&dc,size);a=(int *) malloc(size);  memset(a,0,N*sizeof(int));//rand_ints(a,N);a[0]=10;a[3]=3;b=(int *) malloc(size);  memset(b,0, N*sizeof(int));// rand_ints(b,N);b[0]=2;b[4]=32;c=(int *) malloc(size); //rand_ints(c,N);memset(c,0, N*sizeof(int));cudaMemcpy(da,a,size,cudaMemcpyHostToDevice);cudaMemcpy(db,b,size,cudaMemcpyHostToDevice);add<<<N,1>>>(da,db,dc);               //N blocks  add<<<1,N>>>(da,db,dc);   N threads

cudaMemcpy(c,dc,size,cudaMemcpyDeviceToHost ); for (int i=0; i<20;i++) std::cout<<c[i]<<std::endl; //_syncthreads(); //useless cudaDeviceSynchronize(); free(a); free(b); free(c); cudaFree(da); cudaFree(db); cudaFree(dc); return 0; }

block+thread
#include <thrust/host_vector.h> #include <thrust/device_vector.h> #include <iostream> 

/*

#define N (2048*2048)
#define M 512 // THREADS_PER_BLOCK
…
add<<<N/M, M>>>(d_a, d_b, d_c);

N /M      blocks used
M   threads / block
*/
 const int N=2048*2048;const int M=512;__global__ void add(int *a, int *b,int *c,int n){int index=threadIdx.x+blockIdx.x*blockDim.x;c[index]=a[index]+b[index];if (index<n)  c[index]=a[index]+b[index];//c[threadIdx.x]=a[threadIdx.x]+b[threadIdx.x];}int main(void) { // H has storage for 4 integersint *a,*b,*c;int *da,*db,*dc;int size=N*sizeof(int); //scalar;cudaMalloc((void**)&da,size);cudaMalloc((void**)&db,size);cudaMalloc((void**)&dc,size);a=(int *) malloc(size);  memset(a,0,N*sizeof(int));//rand_ints(a,N);a[0]=10;a[3]=3;b=(int *) malloc(size);  memset(b,0, N*sizeof(int));// rand_ints(b,N);b[0]=2;b[4]=32;c=(int *) malloc(size); //rand_ints(c,N);memset(c,0, N*sizeof(int));cudaMemcpy(da,a,size,cudaMemcpyHostToDevice);cudaMemcpy(db,b,size,cudaMemcpyHostToDevice);add<<<(N+M-1)/M,M>>>(da,db,dc,N);                  cudaMemcpy(c,dc,size,cudaMemcpyDeviceToHost );for (int i=0; i<20;i++)std::cout<<c[i]<<std::endl;//_syncthreads();//uselesscudaDeviceSynchronize();free(a);free(b);free(c);cudaFree(da);cudaFree(db);cudaFree(dc);  return 0; }