strgrp: Add cosine fudge-curve to unify filter comparison spaces

[ccan] / ccan / strgrp / strgrp.c

diff --git a/ccan/strgrp/strgrp.c b/ccan/strgrp/strgrp.c
index 12119a1f276c7e4c4a9776cf061d1b8dfc77eddf..bab8d334a99eb6b0216c22cb806ea61f5b77b624 100644 (file)
--- a/ccan/strgrp/strgrp.c
+++ b/ccan/strgrp/strgrp.c
@@ -108,10 +108,18 @@ strcossim(const int16_t ref[CHAR_N_VALUES], const int16_t key[CHAR_N_VALUES]) {
 
 /* Low-cost filter functions */
 
 
 /* Low-cost filter functions */
 

+static inline double
+cossim_correction(const double s)
+{
+    return -((s - 0.5) * (s - 0.5)) + 0.33;
+}
+

 static inline bool
 should_grp_score_cos(const struct strgrp *const ctx,
         struct strgrp_grp *const grp, const char *const str) {
 static inline bool
 should_grp_score_cos(const struct strgrp *const ctx,
         struct strgrp_grp *const grp, const char *const str) {

-    return ctx->threshold <= strcossim(ctx->pop, grp->pop);
+    const double s1 = strcossim(ctx->pop, grp->pop);
+    const double s2 = s1 + cossim_correction(s1);
+    return ctx->threshold <= s2;

 }
 
 static inline bool
 }
 
 static inline bool