X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/d12142c9dc382512752775d0cca043bb1aef3f86..4c74bb7b6f2398da81ce462cbdfd9c5a77ffa683:/examples/smpi/NAS/EP/randlc.c

diff --git a/examples/smpi/NAS/EP/randlc.c b/examples/smpi/NAS/EP/randlc.c
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+
+/*
+ *    FUNCTION RANDLC (X, A)
+ *
+ *  This routine returns a uniform pseudorandom double precision number in the
+ *  range (0, 1) by using the linear congruential generator
+ *
+ *  x_{k+1} = a x_k  (mod 2^46)
+ *
+ *  where 0 < x_k < 2^46 and 0 < a < 2^46.  This scheme generates 2^44 numbers
+ *  before repeating.  The argument A is the same as 'a' in the above formula,
+ *  and X is the same as x_0.  A and X must be odd double precision integers
+ *  in the range (1, 2^46).  The returned value RANDLC is normalized to be
+ *  between 0 and 1, i.e. RANDLC = 2^(-46) * x_1.  X is updated to contain
+ *  the new seed x_1, so that subsequent calls to RANDLC using the same
+ *  arguments will generate a continuous sequence.
+ *
+ *  This routine should produce the same results on any computer with at least
+ *  48 mantissa bits in double precision floating point data.  On Cray systems,
+ *  double precision should be disabled.
+ *
+ *  David H. Bailey     October 26, 1990
+ *
+ *     IMPLICIT DOUBLE PRECISION (A-H, O-Z)
+ *     SAVE KS, R23, R46, T23, T46
+ *     DATA KS/0/
+ *
+ *  If this is the first call to RANDLC, compute R23 = 2 ^ -23, R46 = 2 ^ -46,
+ *  T23 = 2 ^ 23, and T46 = 2 ^ 46.  These are computed in loops, rather than
+ *  by merely using the ** operator, in order to insure that the results are
+ *  exact on all systems.  This code assumes that 0.5D0 is represented exactly.
+ */
+
+
+/*****************************************************************/
+/*************           R  A  N  D  L  C             ************/
+/*************                                        ************/
+/*************    portable random number generator    ************/
+/*****************************************************************/
+
+double	randlc( double *X, double *A )
+{
+      static int        KS=0;
+      static double	R23, R46, T23, T46;
+      double		T1, T2, T3, T4;
+      double		A1;
+      double		A2;
+      double		X1;
+      double		X2;
+      double		Z;
+      int     		i, j;
+
+      if (KS == 0) 
+      {
+        R23 = 1.0;
+        R46 = 1.0;
+        T23 = 1.0;
+        T46 = 1.0;
+    
+        for (i=1; i<=23; i++)
+        {
+          R23 = 0.50 * R23;
+          T23 = 2.0 * T23;
+        }
+        for (i=1; i<=46; i++)
+        {
+          R46 = 0.50 * R46;
+          T46 = 2.0 * T46;
+        }
+        KS = 1;
+      }
+
+/*  Break A into two parts such that A = 2^23 * A1 + A2 and set X = N.  */
+
+      T1 = R23 * *A;
+      j  = T1;
+      A1 = j;
+      A2 = *A - T23 * A1;
+
+/*  Break X into two parts such that X = 2^23 * X1 + X2, compute
+    Z = A1 * X2 + A2 * X1  (mod 2^23), and then
+    X = 2^23 * Z + A2 * X2  (mod 2^46).                            */
+
+      T1 = R23 * *X;
+      j  = T1;
+      X1 = j;
+      X2 = *X - T23 * X1;
+      T1 = A1 * X2 + A2 * X1;
+      
+      j  = R23 * T1;
+      T2 = j;
+      Z = T1 - T23 * T2;
+      T3 = T23 * Z + A2 * X2;
+      j  = R46 * T3;
+      T4 = j;
+      *X = T3 - T46 * T4;
+      return(R46 * *X);
+} 
+
+
+
+/*****************************************************************/
+/************   F  I  N  D  _  M  Y  _  S  E  E  D    ************/
+/************                                         ************/
+/************ returns parallel random number seq seed ************/
+/*****************************************************************/
+