拜求 CUDA 课程的那个结业证书 nbody题的代码

Question

CUDA 课程的那个结业证书 nbody题的代码，实在没有思路了

Answer 1

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问题回答：

1. CUDA课程的结业证书：请联系你所参加的CUDA课程的授课方，获取课程结业证书。
2. nbody题的代码：针对该问题，以下是一些提高代码解决问题的思路和技巧。 a. 阅读题目：首先仔细阅读题目，理解题目的意思和要求，明确代码解决的问题。 b. 官方文档：查看CUDA官方文档，查找nbody相关内容，了解其算法和实现思路。 c. 范例代码：查找范例代码，了解其实现流程和代码风格，可以从中得到相应的启发和思路。 d. 参数设置：检查参数设置是否合理，如模拟粒子数量等参数，确定参数范围。 e. 优化技巧：使用CUDA加速技术，如使用共享内存等，对代码进行优化，提高程序速度和效率。 相关案例：
3. 官方文档地址：https://docs.nvidia.com/cuda/index.html
4. 范例代码：https://github.com/nvidia/CUDALearning/tree/master/samples/nbody
5. 优化技巧：使用共享内存实现nbody算法，参考代码如下：

__global__ void nbody_kernel_shared(float *pos,
                              float *vel,
                              float dt,
                              uint num_particles)
{
    extern __shared__ float4 sdata[];
    uint gid = blockIdx.x * blockDim.x + threadIdx.x;
    float3 pos_i, vel_i, acc_i;
    acc_i.x = acc_i.y = acc_i.z = 0.f;
    pos_i.x = pos_i.y = pos_i.z = 0.f;
    vel_i.x = vel_i.y = vel_i.z = 0.f;
    if (gid < num_particles)
    {
        float4 r_x, r_y, r_z, r_w;
        float3 ri, rj;
        float distSqr, invDist, invDistCube;
        ri = make_float3(pos[gid]);
        vel_i = make_float3(vel[gid]);
        sdata[threadIdx.x] = make_float4(ri, 0.f);
        __syncthreads();
        for (uint j=0; j < blockDim.x; j++)
        {
            r_x = sdata[j];
            distSqr = (ri.x - r_x.x)*(ri.x - r_x.x) + 
                      (ri.y - r_x.y)*(ri.y - r_x.y) + 
                      (ri.z - r_x.z)*(ri.z - r_x.z) + 
                      EPS;
            invDist = rsqrtf(distSqr);
            invDistCube = invDist * invDist * invDist;
            acc_i.x += (ri.x - r_x.x) * invDistCube;
            acc_i.y += (ri.y - r_x.y) * invDistCube;
            acc_i.z += (ri.z - r_x.z) * invDistCube;
        }
        __syncthreads();
        for (uint b=0; b < blockDim.x; b+=WARP_SIZE) 
        {
            r_y = __shfl(sdata[b+threadIdx.x/WARP_SIZE], (threadIdx.x+0)%WARP_SIZE, WARP_SIZE);     
            r_z = __shfl(sdata[b+threadIdx.x/WARP_SIZE], (threadIdx.x+1)%WARP_SIZE, WARP_SIZE);     
            r_w = __shfl(sdata[b+threadIdx.x/WARP_SIZE], (threadIdx.x+2)%WARP_SIZE, WARP_SIZE);     
            for (uint j=0; j < WARP_SIZE; j++)                          
            {
                rj = make_float3(r_y.x, r_y.y, r_y.z);
                distSqr = (ri.x - rj.x)*(ri.x - rj.x) + 
                          (ri.y - rj.y)*(ri.y - rj.y) + 
                          (ri.z - rj.z)*(ri.z - rj.z) + 
                          EPS;
                invDist = rsqrtf(distSqr);
                invDistCube = invDist * invDist * invDist;
                acc_i.x += (ri.x - rj.x) * invDistCube;
                acc_i.y += (ri.y - rj.y) * invDistCube;
                acc_i.z += (ri.z - rj.z) * invDistCube;
                r_y = r_z;  
                r_z = r_w;  
                r_w = __shfl(sdata[b+threadIdx.x/WARP_SIZE], (j+3)%WARP_SIZE, WARP_SIZE);                                
            }                                                           
        }
        vel_i.x += acc_i.x*dt;
        vel_i.y += acc_i.y*dt;
        vel_i.z += acc_i.z*dt;
        sdata[threadIdx.x] = make_float4(ri + vel_i*dt, 0.f);
        __syncthreads();
        pos[gid] = sdata[threadIdx.x].x;
        pos[gid+num_particles] = sdata[threadIdx.x].y;
        pos[gid+2*num_particles] = sdata[threadIdx.x].z;
        vel[gid] = make_float4(vel_i, 0.f).x;
    }
}