porting of struct and methods

Hello Community.

I have to port a code from C++ to Cuda. The code use an object that use its internal function to do a simulation. This object use mostly simple mathematical function but it use also a lot a random number generator function. I though that I could replace the random function with an internal random function of the object and then use it in the kernel. To show you what I need I wrote a toy model that is an extreme simplification of what I need.

#include <cuda.h>

#include <iostream>

#include <curand_kernel.h>

using namespace std;

struct test{

float value1;

float value2;

curandState B;

float __device__ rand(){return curand_uniform(&B);}


__global__ void setup_kernel(curandState *state)


const int id=blockIdx.x;

curand_init(id, id, 0, &state[id]);


__global__ void fill_mat(struct test *anobj, curandState *state)


 const int Idx=blockIdx.x;

 curandState localState = state[Idx];





int main()


int num=10;

curandState *devStates;

cudaMalloc(  (void **)&devStates, num*sizeof(curandState) );

struct test *results = (struct test*)malloc(num*sizeof(struct test));

struct test *to_device;

cudaMalloc ( (void **)&to_device, num*sizeof(to_device));

setup_kernel<<<num, 1>>>(devStates);

fill_mat<<<num,1>>>(to_device, devStates);

cudaMemcpy(results,to_device,num*sizeof(struct test),cudaMemcpyDeviceToHost);

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



return 0;


I need also that at each call of rand() I get a different random number (so there may be some error in the passage of the B state).

Unfortunately the code that I have put doesn’t work, it give a lot of zeros for for the results.

Could somebody help me to correct this code please?

Problem found (but I still need to run some tests to see if it work completely as I want…).

In practice you need to add a cudaMemcpy from host to device before launch the kernel.

cudaMemcpy(to_device,results,num*sizeof(struct test),cudaMemcpyHostToDevice);