Changeset 0b717c5 in sasmodels for sasmodels/models/bcc_paracrystal.c

Timestamp:

Oct 14, 2016 12:53:59 PM (8 years ago)

Author:

Paul Kienzle <pkienzle@…>

Branches:

master, core_shell_microgels, costrafo411, magnetic_model, ticket-1257-vesicle-product, ticket_1156, ticket_1265_superball, ticket_822_more_unit_tests

Children:

5bddd89

Parents:

ec9d329

Message:

bcc/fcc/sc: slightly slower but more robust calculation of Zq

File:

• sasmodels/models/bcc_paracrystal.c (modified) (1 diff)

sasmodels/models/bcc_paracrystal.c

@@ -98 +98 @@
 
     const double qd = 0.5*q*dnn;
-    const double exp_qd = exp(0.5*square(qd*d_factor)*(a1*a1 + a2*a2 + a3*a3));
-    const double sinh_qd = 0.5*exp_qd - 0.5/exp_qd;
-    const double cosh_qd = 0.5*exp_qd + 0.5/exp_qd;
-
-    const double Zq = sinh_qd/(cosh_qd - cos(qd*a1))
-                    * sinh_qd/(cosh_qd - cos(qd*a2))
-                    * sinh_qd/(cosh_qd - cos(qd*a3));
+    const double arg = 0.5*square(qd*d_factor)*(a1*a1 + a2*a2 + a3*a3);
+    const double tanh_qd = tanh(arg);
+    const double cosh_qd = cosh(arg);
+    const double Zq = tanh_qd/(1. - cos(qd*a1)/cosh_qd)
+                    * tanh_qd/(1. - cos(qd*a2)/cosh_qd)
+                    * tanh_qd/(1. - cos(qd*a3)/cosh_qd);
 
     const double Fq = sphere_form(q,radius,sld,solvent_sld)*Zq;