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authorThomas White <taw@physics.org>2011-05-11 17:27:11 +0200
committerThomas White <taw@physics.org>2012-02-22 15:27:26 +0100
commitbc5fd6907120554ae0649032b5f88461c2b1788f (patch)
tree19c6cb9c558e4161555456cc19ee9b78b89fdd92 /src
parent1f32046f8c429752fe6443e0391044697be4bb08 (diff)
Use Gaussian noise to mess up unit cell
Diffstat (limited to 'src')
-rw-r--r--src/partial_sim.c21
1 files changed, 8 insertions, 13 deletions
diff --git a/src/partial_sim.c b/src/partial_sim.c
index 0fd51eb8..6bf0a2c6 100644
--- a/src/partial_sim.c
+++ b/src/partial_sim.c
@@ -31,25 +31,20 @@
#include "stream.h"
-static int gaussian_noise(double expected, double variance)
+static double gaussian_noise(double expected, double variance)
{
- double x1, x2, w;
- double noise;
+ double x1, x2, noise;
- do {
+ /* A uniformly distributed random number between 0 and 1 */
+ x1 = ((double)random()/RAND_MAX);
+ x2 = ((double)random()/RAND_MAX);
- x1 = 2.0 * ((double)random()/RAND_MAX) - 1.0;
- x2 = 2.0 * ((double)random()/RAND_MAX) - 1.0;
- w = pow(x1, 2.0) + pow(x2, 2.0);
+ noise = sqrt(-2.0*log(x1)) * cos(2.0*M_PI*x2);
- } while ( w >= 1.0 );
-
- w = sqrt((-2.0*log(w))/w);
- noise = w * x1;
-
- return expected + noise*sqrt(variance);
+ return expected + noise*variance;
}
+
static void mess_up_cell(UnitCell *cell)
{
double ax, ay, az;