CUDA notes 1

At work I am getting the chance to experiment with CUDA to speed up some of our computationally expensive tasks. It is both very exciting as well as a very intimidating prospect as we have already invested in a Tesla c2075 board for these tests. While I have played with CUDA in the past, it is still a lot to pick up since there have been significant changes since then, and I was also unable to delve too deeply into it at the time.

To get up to speed quickly I am reading through "CUDA Application Design and Development". One thing that is not covered in the first chapter that I am very interested in is how to time the execution of a kernel. I did find some info on stack overflow about the cudaEvent object. Here is a simple example:

#include <iostream>
using namespace std;
#include <thrust/reduce.h>
#include <thrust/sequence.h>
#include <thrust/device_vector.h>
#include <thrust host_vector.h>

int main(){
 const int N=50000;
 float elapsedTime=0.0;
 cudaEvent_t start, stop;
 cudaEventCreate(&start);
 cudaEventCreate(&stop);

 cudaEventRecord(start, 0) ;//start event timer running
 thrust::device_vector<int> a(N);
 thrust::sequence(a.begin(), a.end(), 0);
 int sumA=thrust::reduce(a.begin(), a.end(), 0);
 cudaEventRecord(stop, 0);
 cudaEventSynchronize(stop);//remember kernels run asynchronously
 cudaEventElapsedTime(&elapsedTime, start, stop);
 
 int sumCheck=0;
 for (int i=0; i<N; i++)sumCheck+=i;

 cudaEventElapsedTime(&elapseTime, start, stop);

 if (sumCheck==sumA)cout<<"Test Succeeded in "<<elapseTime<<" milliseconds!"<<endl;
 else cout<<"Test FAILED"<<endl;

 cudaEventDestroy(start);
 cudaEventDestroy(stop);
 return(0);
}