From 4d8a6e3b8f982c947439958b1d22154012376b76 Mon Sep 17 00:00:00 2001
From: tlatorre <tlatorre@uchicago.edu>
Date: Fri, 19 Oct 2018 10:58:52 -0500
Subject: speed up sin_theta calculation by replacing sin(acos(cos_theta)) with
 sqrt(1-pow(cos_theta,2))

---
 src/scattering.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'src/scattering.c')

diff --git a/src/scattering.c b/src/scattering.c
index 0247c62..c4bdd57 100644
--- a/src/scattering.c
+++ b/src/scattering.c
@@ -158,7 +158,7 @@ double get_probability(double beta, double cos_theta, double theta0)
 
     /* Technically this isn't defined up to a sign, but it doesn't matter since
      * we are going to square it everywhere. */
-    sin_theta = fabs(sin(acos(cos_theta)));
+    sin_theta = sqrt(1-pow(cos_theta,2));
 
     return gsl_spline2d_eval(spline, beta*cos_theta, beta*sin_theta*theta0, xacc, yacc)/(theta0*sin_theta);
 }
-- 
cgit