86 lines
3.2 KiB
MySQL
86 lines
3.2 KiB
MySQL
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-- +----------------------------------------------------------------------------+
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-- | Jeffrey M. Hunter |
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-- | jhunter@idevelopment.info |
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-- | www.idevelopment.info |
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-- |----------------------------------------------------------------------------|
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-- | Copyright (c) 1998-2012 Jeffrey M. Hunter. All rights reserved. |
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-- |----------------------------------------------------------------------------|
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-- | DATABASE : Oracle |
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-- | FILE : plsql_random_numbers.sql |
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-- | CLASS : PL/SQL |
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-- | PURPOSE : PL/SQL implementation of the linear congruential method of |
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-- | generating random numbers. It is in the form of a PL/SQL |
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-- | package, so it should be easy add to existing applications. |
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-- | NOTE : As with any code, ensure to test this script in a development |
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-- | environment before attempting to run it in production. |
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-- +----------------------------------------------------------------------------+
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CREATE OR REPLACE PACKAGE random IS
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-- Returns random integer between [0, r-1]
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FUNCTION rndint(r IN NUMBER) RETURN NUMBER;
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-- Returns random real between [0, 1]
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FUNCTION rndflt RETURN NUMBER;
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END;
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/
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CREATE OR REPLACE PACKAGE BODY random IS
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m CONSTANT NUMBER:=100000000; /* initial conditions */
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m1 CONSTANT NUMBER:=10000; /* (for best results) */
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b CONSTANT NUMBER:=31415821; /* */
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a NUMBER; /* seed */
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the_date DATE; /* */
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days NUMBER; /* for generating initial seed */
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secs NUMBER; /* */
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-- ------------------------
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-- Private utility FUNCTION
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-- ------------------------
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FUNCTION mult(p IN NUMBER, q IN NUMBER) RETURN NUMBER IS
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p1 NUMBER;
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p0 NUMBER;
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q1 NUMBER;
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q0 NUMBER;
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BEGIN
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p1:=TRUNC(p/m1);
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p0:=MOD(p,m1);
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q1:=TRUNC(q/m1);
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q0:=MOD(q,m1);
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RETURN(MOD((MOD(p0*q1+p1*q0,m1)*m1+p0*q0),m));
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END;
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-- ---------------------------------------
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-- Returns random integer between [0, r-1]
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-- ---------------------------------------
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FUNCTION rndint (r IN NUMBER) RETURN NUMBER IS
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BEGIN
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-- Generate a random NUMBER, and set it to be the new seed
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a:=MOD(mult(a,b)+1,m);
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-- Convert it to integer between [0, r-1] and return it
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RETURN(TRUNC((TRUNC(a/m1)*r)/m1));
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END;
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-- ----------------------------------
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-- Returns random real between [0, 1]
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-- ----------------------------------
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FUNCTION rndflt RETURN NUMBER IS
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BEGIN
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-- Generate a random NUMBER, and set it to be the new seed
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a:=MOD(mult(a,b)+1,m);
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RETURN(a/m);
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END;
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BEGIN
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-- Generate initial seed "a" based on system date
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the_date:=SYSDATE;
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days:=TO_NUMBER(TO_CHAR(the_date, 'J'));
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secs:=TO_NUMBER(TO_CHAR(the_date, 'SSSSS'));
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a:=days*24*3600+secs;
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END;
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/
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