From 0897221e282cdfb66f79b9a9539be504574c2a14 Mon Sep 17 00:00:00 2001
From: Thomas White <taw@physics.org>
Date: Thu, 2 May 2013 17:45:20 +0200
Subject: compare_hkl: Calculate CCano only from acentric reflections

---
 libcrystfel/src/symmetry.c | 28 ++++++++++++++++++++++++++++
 libcrystfel/src/symmetry.h |  3 +++
 src/compare_hkl.c          | 16 +++++++++++++++-
 3 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/libcrystfel/src/symmetry.c b/libcrystfel/src/symmetry.c
index 4fdc13c6..81d87b25 100644
--- a/libcrystfel/src/symmetry.c
+++ b/libcrystfel/src/symmetry.c
@@ -1191,6 +1191,34 @@ static int any_negative(signed int h, signed int k, signed int l)
 }
 
 
+/**
+ * is_centric:
+ * @h: h index
+ * @k: k index
+ * @l: l index
+ * @ops: A %SymOpList
+ *
+ * A reflection is centric if it is related by symmetry to its Friedel partner.
+ *
+ * Returns: true if @h @k @l is centric in @ops.
+ *
+ **/
+int is_centric(signed int h, signed int k, signed int l, const SymOpList *ops)
+{
+	signed int ha, ka, la;
+	signed int hb, kb, lb;
+
+	get_asymm(ops, h, k, l, &ha, &ka, &la);
+	get_asymm(ops, -h, -k, -l, &hb, &kb, &lb);
+
+	if ( ha != hb ) return 0;
+	if ( ka != kb ) return 0;
+	if ( la != lb ) return 0;
+
+	return 1;
+}
+
+
 /**
  * get_asymm:
  * @ops: A %SymOpList, usually corresponding to a point group
diff --git a/libcrystfel/src/symmetry.h b/libcrystfel/src/symmetry.h
index 68f17991..6bb6210e 100644
--- a/libcrystfel/src/symmetry.h
+++ b/libcrystfel/src/symmetry.h
@@ -80,6 +80,9 @@ extern const char *symmetry_name(const SymOpList *ops);
 extern void set_symmetry_name(SymOpList *ops, const char *name);
 extern void describe_symmetry(const SymOpList *s);
 
+extern int is_centric(signed int h, signed int k, signed int l,
+                      const SymOpList *ops);
+
 extern void add_symop(SymOpList *ops, IntegerMatrix *m);
 
 #endif	/* SYMMETRY_H */
diff --git a/src/compare_hkl.c b/src/compare_hkl.c
index f91e3cee..986b9617 100644
--- a/src/compare_hkl.c
+++ b/src/compare_hkl.c
@@ -725,7 +725,7 @@ int main(int argc, char *argv[])
 	char *bfile = NULL;
 	char *sym_str = NULL;
 	SymOpList *sym;
-	int ncom, nrej, nneg, nres, nbij;
+	int ncom, nrej, nneg, nres, nbij, ncen;
 	RefList *list1_acc;
 	RefList *list2_acc;
 	RefList *list1;
@@ -948,6 +948,7 @@ int main(int argc, char *argv[])
 	nneg = 0;
 	nres = 0;
 	nbij = 0;
+	ncen = 0;
 	list1_acc = reflist_new();
 	list2_acc = reflist_new();
 	for ( refl1 = first_refl(list1, &iter);
@@ -1018,6 +1019,14 @@ int main(int argc, char *argv[])
 			Reflection *refl1_bij = NULL;
 			Reflection *refl2_bij = NULL;
 			signed int hb, kb, lb;
+			int centric;
+
+			centric = is_centric(h, k, l, sym);
+
+			if ( centric ) {
+				ncen++;
+				continue;
+			}
 
 			if ( find_equiv_in_list(list1, -h, -k, -l, sym,
 			                        &hb, &kb, &lb) )
@@ -1080,6 +1089,11 @@ int main(int argc, char *argv[])
 		       " versions did not have Bijvoet partners.\n", nres);
 	}
 
+	if ( ncen > 0 ) {
+		STATUS("%i reflection pairs rejected because they were"
+		       " centric.\n", ncen);
+	}
+
 	STATUS("%i reflection pairs accepted.\n", ncom);
 
 	resolution_limits(list1_acc, cell, &rmin, &rmax);
-- 
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