Changeset 3097 in Sophya for trunk/SophyaLib/NTools

Timestamp:

Oct 16, 2006, 7:17:55 PM (19 years ago)

Author:

cmv

Message:

precisions sur ComplexGaussRan cmv 16/10/2006

Location:

trunk/SophyaLib/NTools

Files:

• perandom.cc (modified) (1 diff)
• perandom.h (modified) (2 diffs)

trunk/SophyaLib/NTools/perandom.cc

@@ -239 +239 @@
   Les variables aleatoires r,t sont independantes:
     g(r,t) = g(r) g(t) 
-*/
+- Attention:
+La variable complexe "c=x+iy" ainsi definie verifie:
+              <|c|^2> = <c c*> = <x^2+y^2> = <r^2> = 2 sig^2
+Si on veut generer une variable complexe gaussienne telle que
+     <c c*> = s^2 alors il faut sig = s/sqrt(2) comme argument
+*/

trunk/SophyaLib/NTools/perandom.h

@@ -9 +9 @@
 #include "machdefs.h"
 #include <stdlib.h>
+#include <math.h>
 #include "histos.h"
 #include "srandgen.h"
@@ -42 +43 @@
 };
 
-//!  Returns a random gaussian complex number  with variance sig^2
+//! Returns a random complex number such that real and imaginary parts are gaussians with variance sig^2
 inline complex< r_8 > ComplexGaussRan(double sig=1.)
   {return complex< r_8 >(GauRnd(0.,sig),GauRnd(0.,sig));}
+
+//! Returns the module of a random complex number generated by ComplexGaussRan
+inline double ModComplexGaussRan(double sig=1.)
+  {double r=-log(1.-drand01()); return sig*sqrt(2.*r);}
 
 } // namespace SOPHYA