Changeset 73e08ae in sasmodels

Timestamp:

Oct 17, 2016 11:53:08 AM (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:

0b040de

Parents:

92ce163

Message:

core_shell_ellipsoid, cylinder, ellipsoid: code cleanup

Location:

sasmodels/models

Files:

• core_shell_ellipsoid.py (modified) (1 diff)
• cylinder.c (modified) (2 diffs)
• ellipsoid.c (modified) (1 diff)

sasmodels/models/core_shell_ellipsoid.py

@@ -125 +125 @@
 #             ["name", "units", default, [lower, upper], "type", "description"],
 parameters = [
-    ["radius_equat_core","Ang",     20,   [0, inf],    "volume",      "Equatorial radius of core"],
+    ["radius_equat_core","Ang",     20,   [0, inf],   "volume",      "Equatorial radius of core"],
     ["x_core",        "None",       3,   [0, inf],    "volume",      "axial ratio of core, X = r_polar/r_equatorial"],
     ["thick_shell",   "Ang",       30,   [0, inf],    "volume",      "thickness of shell at equator"],

sasmodels/models/cylinder.c

@@ -18 +18 @@
     const double qr = q*radius;
     const double qh = q*0.5*length; 
-    return  sas_J1c(qr*sn) * sinc(qh*cn) ;
+    return sas_J1c(qr*sn) * sinc(qh*cn);
 }
 
@@ -60 +60 @@
     double q, sin_alpha, cos_alpha;
     ORIENT_SYMMETRIC(qx, qy, theta, phi, q, sin_alpha, cos_alpha);
+    //printf("sn: %g cn: %g\n", sin_alpha, cos_alpha);
     const double s = (sld-solvent_sld) * form_volume(radius, length);
-    return 1.0e-4 * square(s * fq(q, sin_alpha, cos_alpha, radius, length));
+    const double form = fq(q, sin_alpha, cos_alpha, radius, length);
+    return 1.0e-4 * square(s * form);
 }

sasmodels/models/ellipsoid.c

@@ -8 +8 @@
 {
     double ratio = radius_polar/radius_equatorial;
-    const double u = q*radius_equatorial*sqrt(1.0
-                   + sin_alpha*sin_alpha*(ratio*ratio - 1.0));
-    const double f = sph_j1c(u);
+    // Given the following under the radical:
+    //     1 + sin^2(T) (v^2 - 1)
+    // we can expand to match the form given in Guinier (1955)
+    //     = (1 - sin^2(T)) + v^2 sin^2(T) = cos^2(T) + sin^2(T)
+    // Instead of using pythagoras we could pass in sin and cos; this may be
+    // slightly better for 2D which has already computed it, but it introduces
+    // an extra sqrt and square for 1-D not required by the current form, so
+    // leave it as is.
+    const double r = radius_equatorial
+                     * sqrt(1.0 + sin_alpha*sin_alpha*(ratio*ratio - 1.0));
+    const double f = sph_j1c(q*r);
 
     return f*f;