ran1.pas

Delphi Pascal 数据挖掘领域算法包 数值算法大全

FUNCTION ran1(VAR idum: integer): real;
(* Programs using RAN1 must declare the following variables
VAR
   glix1,glix2,glix3: integer;
   glr: ARRAY [1..97] OF real;
in the main program. *)
CONST
   m1=259200;
   ia1=7141;
   ic1=54773;
   rm1=3.8580247e-6;   (* 1.0/m1 *)
   m2=134456;
   ia2=8121;
   ic2=28411;
   rm2=7.4373773e-6;   (* 1.0/m2 *)
   m3=243000;
   ia3=4561;
   ic3=51349;
VAR
   j: integer;
BEGIN
   IF  (idum < 0)  THEN BEGIN
      glix1 := (ic1-idum) MOD m1;
      glix1 := (ia1*glix1+ic1) MOD m1;
      glix2 := glix1 MOD m2;
      glix1 := (ia1*glix1+ic1) MOD m1;
      glix3 := glix1 MOD m3;
      FOR j := 1 TO 97 DO BEGIN
         glix1 := (ia1*glix1+ic1) MOD m1;
         glix2 := (ia2*glix2+ic2) MOD m2;
         glr[j] := (glix1+glix2*rm2)*rm1
      END;
      idum := 1
   END;
   glix1 := (ia1*glix1+ic1) MOD m1;
   glix2 := (ia2*glix2+ic2) MOD m2;
   glix3 := (ia3*glix3+ic3) MOD m3;
   j := 1 + (97*glix3) DIV m3;
   IF ((j > 97) OR (j < 1)) THEN BEGIN
      writeln('pause in routine RAN1'); readln
   END;
   ran1 := glr[j];
   glr[j] := (glix1+glix2*rm2)*rm1
END;