C:/Musimathics_local/Musimat/MusimatChapter9/C090703a.cpp File Reference

#include "MusimatChapter9.h"

Go to the source code of this file.

Functions
	MusimatChapter9Section (C090703a)
Void	SeedRandom (Integer s)
Static Void	para1 ()

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Function Documentation

MusimatChapter9Section

(

C090703a

)

Definition at line 2 of file C090703a.cpp.

References para1().

                                 {
Print("*** Seeding the Random Number Generator ***");
/*****************************************************************************

Seeding the Random Number Generator

Unlike the natural sources of randomness, LCRandom() will always produce the 
same sequence with the same initial parameters. 

Different sets of pseudorandom 
sequences can be generated by varying the initial value of x, as with the 
SeedRandom() function defined below.
*****************************************************************************/
        para1(); // Step into this function to continue.
}

Static Void para1

(

)

Definition at line 22 of file C090703a.cpp.

References LCRandom(), and SeedRandom().

                    {
/*****************************************************************************
Below is an example of generating random numbers from a seed value of 100,
resetting the seed to 100, and generating the same three random numbers.
Repeatability is why this is called a pseudorandom number generator.
*****************************************************************************/

        Print("*** Three random numbers based on seed 100 ***");
        SeedRandom( 100 );
        For (Integer i = 0; i < 3; i++ )
                Print( LCRandom() );
        Print("Same three random numbers after resetting the seed to 100:");
        SeedRandom( 100 );
        For (Integer i = 0; i < 3; i++ )
                Print( LCRandom() );

/*****************************************************************************
The SeedRandom() function allows us to set the initial value of x. If we initialize x to a 
parameter such as the current time in seconds from some fixed moment, then we 
start at a different place in the pseudorandom cycle each time (although, of 
course, this is finite, too, because the sequence length is necessarily limited).
*****************************************************************************/

        Print("LCRandom seeded with current time in seconds:");
        SeedRandom( Time() );
        For (Integer i = 0; i < 3; i++ )
                Print( LCRandom() );

/*****************************************************************************
The linear congruential method is simple and efficient, but it is hardly the 
best source of random values. Even ignoring the fact that it repeats, its 
uniformity is not wonderful. Knuth (1973, vol. 2) cautioned, “Random number 
generators should not be chosen at random.” For superior techniques, see 
Press et al. (1988, 210). However, this method is very simple to implement 
and has the advantage over natural random processes of providing the same 
pseudorandom sequence if seeded with the same values.
*****************************************************************************/
}}

Void SeedRandom

(

Integer

s

)

Definition at line 18 of file C090703a.cpp.

References x.

                           { 
        x = s; // set global variable x to seed s
} 

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