loop prediction for gaussian sum spectrum

1 files changed, 69 insertions, 19 deletions

diff --git a/libcrystfel/src/geometry.c b/libcrystfel/src/geometry.c
index e5f33d64..366464fa 100644
--- a/libcrystfel/src/geometry.c
+++ b/libcrystfel/src/geometry.c
@@ -238,6 +238,13 @@ static double random_partiality(signed int h, signed int k, signed int l,
 	return p;
 }
 
+static inline double safe_khalf(const double xl,
+                                const double yl,
+                                const double zl)
+{
+	if (zl>0) return 0.0/0.0;
+	return -(xl*xl+yl*yl+zl*zl) / (2.0*zl);
+}
 
 static Reflection *check_reflection(struct image *image, Crystal *cryst,
                                     signed int h, signed int k, signed int l,
@@ -245,32 +252,74 @@ static Reflection *check_reflection(struct image *image, Crystal *cryst,
                                     Reflection *updateme)
 {
 	Reflection *refl;
-	double R, top;
-	double kmin, kmax, k0, knom, k1, khalf;
+	double R;
+	double knom=0, khalf=0, kpred=0;
 	double dcs, exerr;
+	double partiality = 0, mean_kpred=0, M2_kpred=0;
+	double sumw_k = 0, mean_k = 0, M2_k=0;
+	struct gaussian g;
+	/* this arbitrary value is there to mimic previous behavoir */
+	const double min_partiality = exp(-0.5*1.7*1.7);
 
 	/* Don't predict 000 */
 	if ( (updateme == NULL) && (abs(h)+abs(k)+abs(l) == 0) ) return NULL;
 
-	/* Calculate the limiting wavelengths, lambda0 and lambda1
-	 * = 1/k0 and 1/k1 respectively */
 	R = fabs(crystal_get_profile_radius(cryst));
-	top = R*R - xl*xl - yl*yl - zl*zl;
-	k0 = top/(2.0*(zl+R));
-	khalf = (- xl*xl - yl*yl - zl*zl) / (2.0*zl);
-	k1 = top/(2.0*(zl-R));
-
-	/* The reflection is excited if any of the reflection is within 2sigma
-	 * of the nominal * wavelength of the X-ray beam
-	 * (NB image->bw is full width) */
-	kmin = 1.0/(image->lambda + image->lambda*image->bw);
-	knom = 1.0/image->lambda;
-	kmax = 1.0/(image->lambda - image->lambda*image->bw);
-	if ( (updateme == NULL) && ((k1>kmax) || (k0<kmin)) ) return NULL;
+	assert(spectrum_get_num_gaussians(image->spectrum));
+	for ( int i = 0 ; i!=spectrum_get_num_gaussians(image->spectrum) ; ++i ) {
+		g = spectrum_get_gaussian(image->spectrum, i);
+
+		double exerr2 = 0;
+		/* project lattice point onto ewald sphere */
+	        double x = xl, y = yl, z = zl + g.kcen;
+		double norm = 1.0/sqrt(x*x+y*y+z*z);
+		x*=norm; y*=norm; z*=norm;
+		z-=1;
+		/* width of ewald sphere in the direction of the projection */
+		const double sigma_proj = sqrt(x*x+y*y+z*z)*g.sigma;
+		mean_variance(g.kcen,g.area,&sumw_k,&mean_k,&M2_k);
+		M2_k+=g.area*g.sigma*g.sigma;
+		const double w0 = 1.0/(R*R);
+		const double w1 = 1.0/(sigma_proj*sigma_proj);
+		x*=g.kcen;y*=g.kcen;z*=g.kcen;
+		/* three because the general case fails in extreme cases */
+		if        ( w0 / w1 <= DBL_MIN ) { /* "Laue" corner case */
+			kpred = g.kcen;
+			exerr2 = g.kcen - safe_khalf(xl,yl,zl);
+			exerr2*= exerr2;
+		} else if ( w1 / w0 <= DBL_MIN ) { /* monochromatic corner case */
+			kpred = safe_khalf(xl,yl,zl);
+			exerr2 = g.kcen - kpred;
+			exerr2*= exerr2;
+		} else {                          /* general case */
+			/* closest point on ewald sphere */
+			const double zlp0 = zl>0?zl:0; /* project zl to 0, bit of a hack... */
+			exerr2 = (x-xl)*(x-xl) + (y-yl)*(y-yl) + (z-zl)*(z-zl);
+			/* weighted average between projected lattice point and ewald sphere */
+			x = ( xl  *w0 + x*w1 ) / ( w0 + w1 );
+			y = ( yl  *w0 + y*w1 ) / ( w0 + w1 );
+			z = ( zlp0*w0 + z*w1 ) / ( w0 + w1 );
+			kpred = safe_khalf(x,y,z);
+		}
+		const double sigma2    = R*R + sigma_proj*sigma_proj;
+		const double exponent = - 0.5 * exerr2 / sigma2;
+		const double overlap_integral = exponent < -700.0 ? 0.0 :
+		                                exp( exponent )
+		                              * sqrt( 2 * M_PI * R * R )
+		                              / sqrt( 2 * M_PI * sigma2 );
+		mean_variance(kpred,g.area*overlap_integral,&partiality,&mean_kpred,&M2_kpred);
+	}
+	partiality *= sqrt( ( R*R + M2_k/sumw_k) / ( R*R ) ); /* reverting the lorentz factor */
+	if ( (updateme == NULL) && ( partiality < min_partiality ) ) return NULL;
 
+	kpred = mean_kpred;
 	/* Calculate excitation error */
+	knom = 1.0/image->lambda;
 	dcs = distance3d(0.0, 0.0, -knom, xl, yl, zl);
 	exerr = 1.0/image->lambda - dcs;  /* Loss of precision */
+	/* to estimate excitation error from partiality but loosing sign */
+	/* that seems to be a problem */
+	/* exerr = R * sqrt( - 2 * log( partiality ) ) ; */
 
 	if ( updateme == NULL ) {
 		refl = reflection_new(h, k, l);
@@ -284,7 +333,7 @@ static Reflection *check_reflection(struct image *image, Crystal *cryst,
 	if ( (image->det != NULL) && (updateme != NULL) ) {
 
 		double fs, ss;
-		locate_peak_on_panel(xl, yl, zl, knom,
+		locate_peak_on_panel(xl, yl, zl, kpred,
 		                     get_panel(updateme), &fs, &ss);
 		set_detector_pos(refl, fs, ss);
 
@@ -296,7 +345,7 @@ static Reflection *check_reflection(struct image *image, Crystal *cryst,
 
 		double fs, ss;        /* Position on detector */
 		signed int p;         /* Panel number */
-		p = locate_peak(xl, yl, zl, knom,
+		p = locate_peak(xl, yl, zl, kpred,
 		                image->det, &fs, &ss);
 		if ( p == -1 ) {
 			reflection_free(refl);
@@ -307,7 +356,8 @@ static Reflection *check_reflection(struct image *image, Crystal *cryst,
 
 	}
 
-	set_kpred(refl, knom);
+	khalf = (- xl*xl - yl*yl - zl*zl) / (2.0*zl);
+	set_kpred(refl, kpred);
 	set_khalf(refl, khalf);
 	set_exerr(refl, exerr);
 	set_lorentz(refl, 1.0);