partial_sim: Use flat noise in cell parameters

src/partial_sim.c

@@ -44,15 +44,15 @@ static void mess_up_cell(UnitCell *cell)
 	//cell_print(cell);
 
 	cell_get_reciprocal(cell, &ax, &ay, &az, &bx, &by, &bz, &cx, &cy, &cz);
-	ax = gaussian_noise(ax, cnoise*fabs(ax)/100.0);
-	ay = gaussian_noise(ay, cnoise*fabs(ay)/100.0);
-	az = gaussian_noise(az, cnoise*fabs(az)/100.0);
-	bx = gaussian_noise(bx, cnoise*fabs(bx)/100.0);
-	by = gaussian_noise(by, cnoise*fabs(by)/100.0);
-	bz = gaussian_noise(bz, cnoise*fabs(bz)/100.0);
-	cx = gaussian_noise(cx, cnoise*fabs(cx)/100.0);
-	cy = gaussian_noise(cy, cnoise*fabs(cy)/100.0);
-	cz = gaussian_noise(cz, cnoise*fabs(cz)/100.0);
+	ax = flat_noise(ax, cnoise*fabs(ax)/100.0);
+	ay = flat_noise(ay, cnoise*fabs(ay)/100.0);
+	az = flat_noise(az, cnoise*fabs(az)/100.0);
+	bx = flat_noise(bx, cnoise*fabs(bx)/100.0);
+	by = flat_noise(by, cnoise*fabs(by)/100.0);
+	bz = flat_noise(bz, cnoise*fabs(bz)/100.0);
+	cx = flat_noise(cx, cnoise*fabs(cx)/100.0);
+	cy = flat_noise(cy, cnoise*fabs(cy)/100.0);
+	cz = flat_noise(cz, cnoise*fabs(cz)/100.0);
 	cell_set_reciprocal(cell, ax, ay, az, bx, by, bz, cx, cy, cz);
 
 	//STATUS("Changed:\n");

src/utils.c

@@ -121,6 +121,19 @@ void progress_bar(int val, int total, const char *text)
 }
 
 
+double random_flat(double max)
+{
+	return max * (double)random()/RAND_MAX;
+}
+
+
+double flat_noise(double expected, double width)
+{
+	double noise = random_flat(2.0*width);
+	return expected+noise-width;
+}
+
+
 double gaussian_noise(double expected, double stddev)
 {
 	double x1, x2, noise;

src/utils.h

@@ -91,6 +91,8 @@ extern int assplode(const char *a, const char *delims, char ***pbits,
                     AssplodeFlag flags);
 
 extern void progress_bar(int val, int total, const char *text);
+extern double random_flat(double max);
+extern double flat_noise(double expected, double width);
 extern double gaussian_noise(double expected, double stddev);
 extern int poisson_noise(double expected);