（インテルCPUの）三角関数は不要 http://blog.unfindable.net/archives/8991

cuda-cos-vs-fcos.cu

//On Ubuntu, you need to install CUDA and:
//sudo apt-get install libboost-dev
//On Windows, I don't know the way to build this code.

#include <iostream>
#include <iomanip>
#include <cmath>
#include <cuda_runtime.h>
#include <boost/multiprecision/cpp_dec_float.hpp>

using namespace std;
using namespace boost::multiprecision;
typedef number<cpp_dec_float<30> >decimal;

__global__ void mycos(const double *in, double *out, int length)
{
  int index = blockDim.x * blockIdx.x + threadIdx.x;
  if (index < length) {
    out[index] = cos(in[index]);
  }
}

int main(void)
{
  srand((unsigned) time(NULL));
  int c1BetterCase = 0;
  int c2BetterCase = 0;
  const int n = 100;
  size_t size = n * sizeof(double);

  double *in = (double *) malloc(size);
  double *out = (double *) malloc(size);
  double *d_in = NULL;
  cudaMalloc((void **) &d_in, size);
  double *d_out = NULL;
  cudaMalloc((void **) &d_out, size);

  for (int i = 0; i < n; ++i) {
    in[i] = rand() / (double) RAND_MAX;
  }
  cudaMemcpy(d_in, in, size, cudaMemcpyHostToDevice);

  mycos<<<16, 16>>>(d_in, d_out, n);
  cudaMemcpy(out, d_out, size, cudaMemcpyDeviceToHost);

  for (int i = 0; i < n; ++i) {
    double x = in[i];
    double c1 = out[i];
    double c2 = 0;
    asm("fcos" : "=&t" (c2) : "f" (x));
    decimal c = cos(decimal(x));
    if (c1 != c2) {
      decimal delta1 = abs(c - decimal(c1));
      decimal delta2 = abs(c - decimal(c2));
      if (delta1 < delta2) ++c1BetterCase;
      else ++c2BetterCase;
      cout << "x = " << setprecision(20) << x << endl <<
        "c1 = cuda cos(x) = " << c1 << endl <<
        "c2 = fcos(x)     = " << c2 << endl <<
        "c  = mp::cos(x)  = " << c.str() << endl << setprecision(5) <<
        "abs(c - c1) = " << delta1 << endl <<
        "abs(c - c2) = " << delta2 << endl << endl;
    }
  }
  cout << "c1 is better: " << c1BetterCase << endl;
  cout << "c2 is better: " << c2BetterCase << endl;
  cout << "total: " << n << endl;

  cudaFree(d_in);
  cudaFree(d_out);
  free(in);
  free(out);
  cudaDeviceReset();
  return 0;
}