code example
SSE IA SIMD instructions

#include <xmmintrin.h>


int main(int argc, char *argv[]) {
  int n = ...;
  float *x, *y;
  x = new float[n+1];
  y = new float[n+1];

  ... // fill x, y

  // do computation
  float ve[4] = {0, 0, 0, 0};
  float e = 0;
  for (int i=1; i<n; i+=4) {
   float half =.5;
   _mm_store_ps(&x[i],
     _mm_mul_ps(_mm_load1_ps(&half),
       _mm_add_ps(_mm_loadu_ps(&y[i+1]),
         _mm_loadu_ps(&y[i-1]))));
   _mm_store_ps(&ve[0],
     _mm_add_ps(_mm_load_ps(&ve[0]),
       _mm_mul_ps(_mm_load_ps(&y[i]),
         _mm_load_ps(&y[i]))));
  }
  e += ve[0] + ve[1] + ve[2] + ve[3];

  ... // output x, e

  delete[] x, y;
  return 0;
}

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