RND function always gives the same sequence of numbers...

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Brana
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RND function always gives the same sequence of numbers...

Post by Brana » Mon Apr 16, 2012 12:53 am

If I launch the Euphoric Emulator and do the simple:

PRINT INT(1+RND(1)*1000)

I will always get the different number...

Hovewer, If I make a simple BASIC program as this one:

3 FOR A = 1 TO 10
4 S = INT (1+RND(1)*1000)
5 PRINT S
6 NEXT A

and save it as a TAP file,
then If I doubleclick on that file from within the My Computer, Euphoric Emulator will launch and run my program, but in this case IT WILL ALWAYS GIVE THE SAME SEQUENCE OF NUMBERS!?

Why is this happening?

Is there anything I could do to have DIFFERENT sequence of numbers generated by RND function in the BASIC program that is started by a doubleclick of the mouse from My Computer?

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Re: RND function always gives the same sequence of numbers..

Post by Antiriad2097 » Mon Apr 16, 2012 6:47 am

The latter is true of the real hardware, it always generates the same list of 'random' numbers from a given seed.

I'm not sure why your first example is giving true random results.

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Re: RND function always gives the same sequence of numbers..

Post by Symoon » Mon Apr 16, 2012 7:15 pm

It's because, when you run Euphoric directly with your program, Euphoric is always in the exact same state so the random function will always give the same results. This probably doesn't happen with real hardware, nor if Euphoric works a bit before running the program - though I don't exactly know what is used by the random function to, obviously, simulate random.

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Chema
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Re: RND function always gives the same sequence of numbers..

Post by Chema » Mon Apr 16, 2012 7:30 pm

I think you are right Symoon. All the procedural random generators which start from a given seed act like that. Will probably happen on the real hardware too, unless some kind of source is used to generate the seed (such as VIA timers). But even with that, I doubt it will change anything when using emulators, as the state is always the same.

My latest random generator uses the VIA and other quite random bits, but you'll have the same sequence with euphoric unless you have some kind of user interaction (which changes timings between calls).

Oh, and even being able to change the seed by program (don't know if this is possible, but should be by pokeing somehting into an address), that won't help Brana. He will have the same thing happening again and again unless he does something like a loop asking for a keypress and keep calling RND(1) inside the loop. At least the sequence will start at a different position...

I wonder if something could be done if Euphoric is emulating a hardware real-time clock... :roll:

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Re: RND function always gives the same sequence of numbers..

Post by Brana » Mon Apr 16, 2012 11:46 pm

Remember my short program from the beginning of this post?

3 FOR A = 1 TO 10
4 S = INT (1+RND(1)*1000)
5 PRINT S
6 NEXT A

If I add the following line at the beginning of the program:

2 INPUT "Please input some random word here";WRD$

so the program looks like this:

2 INPUT "Please input some random word here";WRD$
3 FOR A = 1 TO 10
4 S = INT (1+RND(1)*1000)
5 PRINT S
6 NEXT A

This way the typing speed of the user and the number of keystrokes that he would make - would contribute the different state of the Emulator, right?

But no - even in this case - I STILL GET THE SAME SEQUENCE OF NUMBERS!?

P.S. I DO emulate a real-time clock in Euphoric.ini file... :)

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Re: RND function always gives the same sequence of numbers..

Post by Igotafro » Tue Apr 17, 2012 12:02 am

You're using RND(1), that is, RND with a seed of 1. It should always generate the same sequence of numbers.
What you need is a way of getting a random number to replace the 1.
Just make a loop which increases a variable and at the same time waits for the user to press a key.
Then use that variable instead of 1 in RND(1).

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Re: RND function always gives the same sequence of numbers..

Post by Antiriad2097 » Tue Apr 17, 2012 6:43 am

As I suggested earlier, the real hardware does the same thing.

The RND function will generate the same list of numbers, starting at the same point.

iirc, you can use RND (1) for example, then RND (3), but if you go back to RND (1) it'll start again with the same list of numbers from the beginning (I think, its been a while)

In the example you'd given, inputting a word doesn't change your RND statement. If you asked for a number and used that as your seed, you'd get variable results (though the same one if the same number was entered at the start).

Simpler to run a loop until a key is pressed and use it to either run through your RND function in the loop so its start point is a variable position through the list (depending on where the user stopped it), or count the number of loops and use that number as the seed for your RND following.

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Re: RND function always gives the same sequence of numbers..

Post by Chema » Tue Apr 17, 2012 10:07 am

I am not sure that the Oric's RND function works like that. In the Oric-1 manual it says:
RND(n) will produce a random number greater than or equal to 0
and less than 1, if n is a positive number. If n is a negative number,
then the random seed is set to a particular number, and subsequent
positive n’s will always produce the same sequence. If n is zero, the
last random number generated will be produced.
So there's no difference in RND(1) or RND(3). And I even did not know that a negative number set the seed.

Anyway, still the problem is not solved.

But, can't a Real-time clock extension be emulated with Euphoric? I know nothing about it, but if you can get the seconds (or milliseconds) or the current time of day by peeking somewhere, you can use that as a seed to initialize the RND generator differently in every run... could that be done?

EDIT: Forgot to copy the usage of RND(0) in the quoted text

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Re: RND function always gives the same sequence of numbers..

Post by Brana » Wed Apr 18, 2012 3:56 am

Yes, and they are:

PEEK (869) = date (example 31)
PEEK (868) = month (example 10)
PEEK (870) = Year (example 12 for 2012)
PEEK (865) = Hour, and
PEEK (866) = minute

But, how would I integrate it in to the RND function?

Would something like this:

4 S = INT (1+RND(PEEK(866))*1000)

solve the problem?

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Re: RND function always gives the same sequence of numbers..

Post by Antiriad2097 » Wed Apr 18, 2012 6:59 am

Chema wrote:So there's no difference in RND(1) or RND(3).
My bad, must be mixing up my BASICs. I know one of them resets to the same point if you change the seed, maybe that was Speccy.

I remember having to work round the lack of truly random function using loops until a key was pressed to work to a random point in the list.

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Re: RND function always gives the same sequence of numbers..

Post by Chema » Wed Apr 18, 2012 8:36 am

Brana wrote:
Would something like this:

4 S = INT (1+RND(PEEK(866))*1000)

solve the problem?
Well it would need a try. Not having also a seconds counter is a problem (you'll get the same value during a whole minute), but I'd do something like:

1 RND(-PEEK(866))

Which should reset the seed to a "position" related to the minute of day.

Or, as Antiriad said, use a loop which waits for a keypress and which calls RND inside. Or combine both...

Code: Select all

10 REPEAT
20 I=RND(1)
30 UNTIL KEY$<>""
40 RND(-PEEK(866)+I)
Not sure the above code is correct, but you should get the idea. Also you can add in line 40 the value of one of the VIA counters (for instance at $308, by PEEK(#308) ) to add more sources of randomness :)

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