static float inner_prod(float *x, float *y, int len)
static float inner_prod(spx_sig_t *x, spx_sig_t *y, int len)
static float inner_prod(float *x, float *y, int len){   int i;   float sum1=0,sum2=0,sum3=0,sum4=0;   for (i=0;i<len;)   {      sum1 += x[i]*y[i];      sum2 += x[i+1]*y[i+1];      sum3 += x[i+2]*y[i+2];      sum4 += x[i+3]*y[i+3];      i+=4;   }   return sum1+sum2+sum3+sum4;}