scalar add
#include
#include
#include
__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 integers
int 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<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 " < std::endl;
// print contents of H
for(int i = 0; i "H[" <"] = " < std::endl;
// resize H
H.resize(2);
std::cout <<"H now has 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[" <"] = " < std::endl;
// H and D are automatically deleted when the function returns
return 0; }
block or thread
#include
#include
#include
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 integers
int *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<<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<std::endl; //_syncthreads(); //useless cudaDeviceSynchronize(); free(a); free(b); free(c); cudaFree(da); cudaFree(db); cudaFree(dc); return 0; }
block+thread
#include
#include
#include
/*
#define N (2048*2048)
#define M 512 // THREADS_PER_BLOCK
…
add<<>>(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 integers
int *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<std::endl;
//_syncthreads();
//useless
cudaDeviceSynchronize();
free(a);
free(b);
free(c);
cudaFree(da);
cudaFree(db);
cudaFree(dc);
return 0; }
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