ComputeFstat_DemodHL_OptC.c File Reference

Akos generic hotloop code (Dterms <= 20) More...

Detailed Description

Akos generic hotloop code (Dterms <= 20)

/* NOTE: sin[ 2pi (Dphi_alpha - k) ] = sin [ 2pi Dphi_alpha ], therefore
 * the trig-functions need to be calculated only once!
 * We choose the value sin[ 2pi(Dphi_alpha - kstar) ] because it is the
 * closest to zero and will pose no numerical difficulties !
 */
{
  {
    /* improved hotloop algorithm by Fekete Akos:
     * take out repeated divisions into a single common denominator,
     * plus use extra cleverness to compute the nominator efficiently...
     */
    REAL4 kappa_max = kappa_star + 1.0f * Dterms - 1.0f;
    REAL4 Sn = crealf(*Xalpha_l);
    REAL4 Tn = cimagf(*Xalpha_l);
    REAL4 pn = kappa_max;
    REAL4 qn = pn;
    REAL4 U_alpha, V_alpha;
 
    /* recursion with 2*Dterms steps */
    UINT4 l;
    for ( l = 1; l < 2*Dterms; l ++ )
      {
        Xalpha_l ++;
        pn = pn - 1.0f;                         /* p_(n+1) */
        Sn = pn * Sn + qn * crealf(*Xalpha_l);  /* S_(n+1) */
        Tn = pn * Tn + qn * cimagf(*Xalpha_l);  /* T_(n+1) */
        qn *= pn;                               /* q_(n+1) */
      } /* for l < 2*Dterms */
 
    { /* only one division left */
      REAL4 r_qn = 1.0 / qn;
      U_alpha = Sn * r_qn;
      V_alpha = Tn * r_qn;
    }
 
    /* NOTE: sin[ 2pi (Dphi_alpha - k) ] = sin [ 2pi Dphi_alpha ] = sin [ 2pi kappa_star ],
     * therefore the trig-functions need to be calculated only once!
     * We choose the value sin[ 2pi kappa_star ] because it is the
     * closest to zero and will pose no numerical difficulties !
     * As kappa in [0, 1) we can skip the trimming step.
     */
    REAL4 s_alpha, c_alpha;   /* sin(2pi kappa_alpha) and (cos(2pi kappa_alpha)-1) */
    XLALSinCos2PiLUTtrimmed ( &s_alpha, &c_alpha, kappa_star);
    c_alpha -= 1.0f;
 
    realXP = s_alpha * U_alpha - c_alpha * V_alpha;
    imagXP = c_alpha * U_alpha + s_alpha * V_alpha;
  }
 
  /* real- and imaginary part of e^{i 2 pi lambda_alpha } */
  XLALSinCos2PiLUT ( &imagQ, &realQ, lambda_alpha );
}

Definition in file ComputeFstat_DemodHL_OptC.c.

Go to the source code of this file.

Macros
#define	FUNC   XLALComputeFaFb_OptC
#define	HOTLOOP_SOURCE   "ComputeFstat_DemodHL_OptC.i"

Macro Definition Documentation

FUNC

#define FUNC   XLALComputeFaFb_OptC

Definition at line 37 of file ComputeFstat_DemodHL_OptC.c.

HOTLOOP_SOURCE

#define HOTLOOP_SOURCE   "ComputeFstat_DemodHL_OptC.i"

Definition at line 38 of file ComputeFstat_DemodHL_OptC.c.