 
 #include <iostream>
 
+// we could vary M & N to find the perf sweet spot
 
-// we could vary M & N to find the perf sweet spot
+__host__ __device__
+unsigned int hash(unsigned int a)
+{
+    a = (a+0x7ed55d16) + (a<<12);
+    a = (a^0xc761c23c) ^ (a>>19);
+    a = (a+0x165667b1) + (a<<5);
+    a = (a+0xd3a2646c) ^ (a<<9);
+    a = (a+0xfd7046c5) + (a<<3);
+    a = (a^0xb55a4f09) ^ (a>>16);
+    return a;
+}
 
 struct estimate_pi
 {
   __host__ __device__
-  float operator()(unsigned int seed)
+  float operator()(unsigned int thread_id)
   {
     using namespace thrust::experimental::random;
 
     float sum = 0;
-    unsigned int N = 10000;
+    unsigned int N = 10000; // samples per thread
+
+    unsigned int seed = hash(thread_id);
 
     // seed a random number generator
     // XXX use this with uniform_01

    for(unsigned int i = 0; i < N; ++i)
    {
      // draw a sample from the unit square
      float u0 = static_cast<float>(rng()) / minstd_rand::max;
      float u1 = static_cast<float>(rng()) / minstd_rand::max;

      // measure distance from the origin
      float dist = sqrtf(u0*u0 + u1*u1);

      // add 1.0f if (u0,u1) is inside the unit circle
      if(dist <= 1.0f)
        sum += 1.0f;
    }

int main(void)
{
  // use 30K independent seeds
  int M = 30000;

  float estimate = thrust::transform_reduce(thrust::counting_iterator<int>(0),
                                            thrust::counting_iterator<int>(M),
                                            estimate_pi(),
                                            0.0f,
                                            thrust::plus<float>());
