From b3854b29262d2f67eae90c1e54b39b09e49ea66b Mon Sep 17 00:00:00 2001
From: Thomas White <taw@physics.org>
Date: Wed, 7 Jul 2010 16:51:26 +0200
Subject: compare_hkl: Use minimisation to determine the right scale factor

---
 src/statistics.c | 171 +++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 142 insertions(+), 29 deletions(-)

(limited to 'src/statistics.c')

diff --git a/src/statistics.c b/src/statistics.c
index d78dde9e..da3d95c4 100644
--- a/src/statistics.c
+++ b/src/statistics.c
@@ -16,11 +16,27 @@
 
 #include <math.h>
 #include <stdlib.h>
+#include <gsl/gsl_errno.h>
+#include <gsl/gsl_min.h>
 
 #include "statistics.h"
 #include "utils.h"
 
 
+struct r_params {
+	const double *ref1;
+	const unsigned int *c1;
+	const double *ref2;
+	const unsigned int *c2;
+	int fom;
+};
+
+enum {
+	R_2,
+	R_MERGE,
+};
+
+
 double stat_scale_intensity(const double *ref1, const unsigned int *c1,
                             const double *ref2, const unsigned int *c2)
 {
@@ -45,38 +61,39 @@ double stat_scale_intensity(const double *ref1, const unsigned int *c1,
 }
 
 
-double stat_r2(const double *ref1, const unsigned int *c1,
-               const double *ref2, const unsigned int *c2, double *scalep)
+double stat_scale_sqrti(const double *ref1, const unsigned int *c1,
+                            const double *ref2, const unsigned int *c2)
 {
 	double top = 0.0;
 	double bot = 0.0;
-	double scale;
 	int i;
-	scale = stat_scale_intensity(ref1, c1, ref2, c2);
-	*scalep = scale;
 
 	/* Start from i=1 -> skip central beam */
 	for ( i=1; i<LIST_SIZE; i++ ) {
 
 		if ( c1[i] && c2[i] ) {
 
-			double i1, i2;
-			i1 = ref1[i] / (scale*(double)c1[i]);
-			i2 = ref2[i] / (double)c2[i];
+			double f1, f2;
 
-			top += pow(fabs(i1 - i2), 2.0);
-			bot += pow(i1, 2.0);
+			if ( (ref1[i]<0.0) || (ref2[i]<0.0) ) continue;
 
-		} /* else reflection not measured so don't worry about it */
+			f1 = sqrt(ref1[i]) / (double)c1[i];
+			f2 = sqrt(ref2[i]) / (double)c2[i];
+
+			top += f1 * f2;
+			bot += f2 * f2;
+
+		} /* else reflection not common so don't worry about it */
 
 	}
 
-	return sqrt(top/bot);
+	return top/bot;
 }
 
 
-double stat_scale_sqrti(const double *ref1, const unsigned int *c1,
-                            const double *ref2, const unsigned int *c2)
+static double internal_r2(const double *ref1, const unsigned int *c1,
+                          const double *ref2, const unsigned int *c2,
+                          double scale)
 {
 	double top = 0.0;
 	double bot = 0.0;
@@ -87,33 +104,28 @@ double stat_scale_sqrti(const double *ref1, const unsigned int *c1,
 
 		if ( c1[i] && c2[i] ) {
 
-			double f1, f2;
-
-			if ( (ref1[i]<0.0) || (ref2[i]<0.0) ) continue;
-
-			f1 = sqrt(ref1[i]) / (double)c1[i];
-			f2 = sqrt(ref2[i]) / (double)c2[i];
+			double i1, i2;
+			i1 = ref1[i] / (scale*(double)c1[i]);
+			i2 = ref2[i] / (double)c2[i];
 
-			top += f1 * f2;
-			bot += f2 * f2;
+			top += pow(fabs(i1 - i2), 2.0);
+			bot += pow(i1, 2.0);
 
-		} /* else reflection not common so don't worry about it */
+		} /* else reflection not measured so don't worry about it */
 
 	}
 
-	return top/bot;
+	return sqrt(top/bot);
 }
 
 
-double stat_rmerge(const double *ref1, const unsigned int *c1,
-                   const double *ref2, const unsigned int *c2, double *scalep)
+static double internal_rmerge(const double *ref1, const unsigned int *c1,
+                              const double *ref2, const unsigned int *c2,
+                              double scale)
 {
 	double top = 0.0;
 	double bot = 0.0;
-	double scale;
 	int i;
-	scale = stat_scale_sqrti(ref1, c1, ref2, c2);
-	*scalep = scale;
 
 	/* Start from i=1 -> skip central beam */
 	for ( i=1; i<LIST_SIZE; i++ ) {
@@ -136,3 +148,104 @@ double stat_rmerge(const double *ref1, const unsigned int *c1,
 
 	return 2.0*top/bot;
 }
+
+
+static double calc_r(double scale, void *params)
+{
+	struct r_params *rp = params;
+
+	switch ( rp->fom) {
+	case R_MERGE :
+		return internal_rmerge(rp->ref1, rp->c1,
+		                       rp->ref2, rp->c2, scale);
+	case R_2 :
+		return internal_r2(rp->ref1, rp->c1,
+		                   rp->ref2, rp->c2, scale);
+	}
+
+	ERROR("No such FoM!\n");
+	abort();
+}
+
+
+static double r_minimised(const double *ref1, const unsigned int *c1,
+                          const double *ref2, const unsigned int *c2,
+                          double *scalep, int fom)
+{
+	gsl_function F;
+	gsl_min_fminimizer *s;
+	int status;
+	double scale = 1.0;
+	struct r_params rp;
+	int iter = 0;
+
+	rp.ref1 = ref1;
+	rp.ref2 = ref2;
+	rp.c1 = c1;
+	rp.c2 = c2;
+	rp.fom = fom;
+
+	F.function = &calc_r;
+	F.params = &rp;
+
+	s = gsl_min_fminimizer_alloc(gsl_min_fminimizer_brent);
+
+	/* Initial guess */
+	switch ( fom ) {
+	case R_MERGE :
+		scale = stat_scale_sqrti(ref1, c1, ref2, c2);
+		break;
+	case R_2 :
+		scale = stat_scale_intensity(ref1, c1, ref2, c2);
+		break;
+	}
+	//STATUS("Initial scale factor estimate: %5.2e\n", scale);
+
+	/* Probably within an order of magnitude either side */
+	gsl_min_fminimizer_set(s, &F, scale, scale/10.0, scale*10.0);
+
+	do {
+
+		double lo, up;
+
+		/* Iterate */
+		gsl_min_fminimizer_iterate(s);
+
+		/* Get the current estimate */
+		scale = gsl_min_fminimizer_x_minimum(s);
+		lo = gsl_min_fminimizer_x_lower(s);
+		up = gsl_min_fminimizer_x_upper(s);
+
+		/* Check for convergence */
+		status = gsl_min_test_interval(lo, up, 0.001, 0.0);
+
+		iter++;
+
+	} while ( status == GSL_CONTINUE );
+
+	if (status != GSL_SUCCESS) {
+		ERROR("Scale factor minimisation failed.\n");
+	}
+
+	gsl_min_fminimizer_free(s);
+
+	//STATUS("Final scale factor: %5.2e\n", scale);
+	*scalep = scale;
+	return calc_r(scale, &rp);
+}
+
+
+double stat_rmerge(const double *ref1, const unsigned int *c1,
+                   const double *ref2, const unsigned int *c2,
+                   double *scalep)
+{
+	return r_minimised(ref1, c1, ref2, c2, scalep, R_MERGE);
+}
+
+
+double stat_r2(const double *ref1, const unsigned int *c1,
+               const double *ref2, const unsigned int *c2,
+               double *scalep)
+{
+	return r_minimised(ref1, c1, ref2, c2, scalep, R_2);
+}
-- 
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