Changeset a5899c8 in sasmodels

Timestamp:

Nov 25, 2015 4:27:24 PM (9 years ago)

Author:

Paul Kienzle <pkienzle@…>

Branches:

master, core_shell_microgels, costrafo411, magnetic_model, release_v0.94, release_v0.95, ticket-1257-vesicle-product, ticket_1156, ticket_1265_superball, ticket_822_more_unit_tests

Children:

1ec7efa

Parents:

4b41184

Message:

use taylor expansion in ellipsoid model so single precision is more accurate

File:

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

sasmodels/models/ellipsoid.c

@@ -12 +12 @@
                    + cos_alpha*cos_alpha*(ratio*ratio - 1.0));
     SINCOS(u, sn, cn);
-    const double f = ( u==0.0 ? 1.0 : 3.0*(sn-u*cn)/(u*u*u) );
+    //const double f = ( u==0.0 ? 1.0 : 3.0*(sn-u*cn)/(u*u*u) );
+    const double usq = u*u;
+    const double f = (u < 1e-1)
+        ? 1.0 + usq*(-3./30. + usq*(3./840. + usq*(-3./45360.)))// + qrsq*(3./3991680.))))
+        : 3.0*(sn/u - cn)/usq;
     return f*f;
 }