Changeset ef2861b in sasmodels for sasmodels/models/cylinder.c

Timestamp:

Oct 31, 2014 2:43:39 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:

ba69383

Parents:

994d77f

Message:

cylinder performance tweak

File:

• sasmodels/models/cylinder.c (modified) (4 diffs)

sasmodels/models/cylinder.c

@@ -7 +7 @@
 // besarg = q * R * sin(alpha)
 // siarg = q * L/2 * cos(alpha)
-double _cyl(double twovd, double besarg, double siarg);
-double _cyl(double twovd, double besarg, double siarg)
+double _cyl(double besarg, double siarg);
+double _cyl(double besarg, double siarg)
 {
     const double bj = (besarg == 0.0 ? 0.5 : J1(besarg)/besarg);
     const double si = (siarg == 0.0 ? 1.0 : sin(siarg)/siarg);
-    return twovd*si*bj;
+    return si*bj;
 }
 
@@ -28 +28 @@
     const double qr = q*radius;
     const double qh = q*0.5*length;
-    const double twovd = 2.0*(sld-solvent_sld)*form_volume(radius, length);
     double total = 0.0;
     // double lower=0, upper=M_PI_2;
@@ -37 +36 @@
         double sn, cn;
         SINCOS(alpha, sn, cn);
-        const double fq = _cyl(twovd, qr*sn, qh*cn);
+        // For a bit of efficiency, we are moving the 2 V delta rho constant
+        // factor, 2Vd, out of the loop, so this is fq/2Vd rather than fq.
+        const double fq = _cyl(qr*sn, qh*cn);
         total += Gauss76Wt[i] * fq * fq * sn;
     }
     // translate dx in [-1,1] to dx in [lower,upper]
     //const double form = (upper-lower)/2.0*total;
-    return 1.0e-4 * total * M_PI_4;
+    const double twovd = 2.0*(sld-solvent_sld)*form_volume(radius, length);
+    return 1.0e-4 * twovd * twovd * total * M_PI_4;
 }
 
@@ -62 +64 @@
     SINCOS(theta*M_PI_180, sn, cn);
     const double q = sqrt(qx*qx+qy*qy);
-    const double cos_val = cn*cos(phi*M_PI_180)*(qx/q) + sn*(qy/q);
+    const double cos_val = (q==0. ? 1.0 : (cn*cos(phi*M_PI_180)*qx + sn*qy)/q);
     const double alpha = acos(cos_val);
+    SINCOS(alpha, sn, cn);
+    //sn = sqrt(1.0 - cos_val*cos_val);
+    //sn = 1.0 - 0.5*cos_val*cos_val;  // if cos_val is very small
+    //cn = cos_val;
 
     const double twovd = 2.0*(sld-solvent_sld)*form_volume(radius, length);
-    SINCOS(alpha, sn, cn);
-    const double fq = _cyl(twovd, q*radius*sn, q*0.5*length*cn);
+    const double fq = twovd * _cyl(q*radius*sn, q*0.5*length*cn);
     return 1.0e-4 * fq * fq;
 }