Can you get truly random numbers from Dynamics NAV?

josephdewey · **Posted:** Wed May 09, 2012 12:05 am

I use random numbers for testing a lot, and I'm used to Excel, where you can get a lot of precision from '=RAND()'

It seems like the easiest way to replicate the Excel RAND function in Navision is with this code:

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RANDOMIZE;
x :=  RANDOM(2147483647)/2147483647)

And, then this really isn't a true random number, but it's based on an algorithm that wouldn't pass really advanced randomness tests.

Is there something better in Navision than RANDOM? Or, do you know if future versions of Navision will support random numbers that are more random?

manjusree · **Joined:** Tue Jun 23, 2009 6:51 am **Posts:** 47

Hope this helps

:-

RandomDigit := CREATEGUID;
RandomDigit := DELCHR(RandomDigit,'=','{}-01');
RandomDigit := COPYSTR(RandomDigit,1,10);

kriki · **Posted:** Wed May 09, 2012 9:24 am

Well, also GUID is not really random, but it probably is more random than RANDOM.

Sog · **Posted:** Wed May 09, 2012 10:14 am

take the last digit of currentdatetime, (the ones after the decimal seperator).
Guaranteed to be random.

kriki · **Posted:** Wed May 09, 2012 11:54 am

or also with TIME.

I tried this code:

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for i := 1 to 1000000 do begin
  tim := time;
  tim2 := 000000T;
  int := (tim - tim2) MOD 1000;

  tmpInteger.Number := int;
  if tmpInteger.insert then ;
end;

message('%1',tmpInteger.count);

With this I wanted to see if the last 2 digits (the milliseconds) can have all values and the count is always close to 1000. So this is not a bad system.

josephdewey · **Posted:** Thu May 10, 2012 8:11 pm

Using the last digit of the thousands in TIME (the milliseconds count) to generate a random number is definitely a unique approach. The biggest problem with this, though, is that Navision does many calculations per millisecond, so even though this would probably generate a random enough number between 0 and 9, then it kind of falls apart when you need something outside of the 0 to 9 range, or if you need multiple numbers.

But, I did make a working prototype that gives pretty random numbers. It's pretty slow, and I would guess that it wouldn't pass too many heavy-duty randomness tests. Also, about half of the time this gives a number with far fewer decimal places than the max. I don't understand why my code does that.

But the numbers it generates do look random.

Code: Select all

FOR j := 1 TO 10 DO BEGIN
  rand_string := '0.';
  FOR i := 1 TO 20 DO BEGIN
    rand_string := rand_string + COPYSTR(FORMAT(TIME,0,'<Thousands>'),3,1);
    SLEEP(1); //try removing this to see what happens
  END;
  EVALUATE(rand_dec, rand_string);
  MESSAGE('%1',rand_dec);
END;

Thanks for your ideas!

kapamarou · **Posted:** Thu May 10, 2012 9:19 pm

Were do you need to use such a generator?

I guess you could use some dll file that does only than, or even use Excel automation to generate a random number...

josephdewey · **Posted:** Fri May 11, 2012 12:37 am

Here's my code for using the CREATEGUID to get a random number between 0 and 1.

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FOR j := 1 TO 10 DO BEGIN
  rand_string := '0.';
  WHILE STRLEN(rand_string) < 20 DO
    rand_string := rand_string + DELCHR(CREATEGUID,'=','{}-ABCDEF');
  EVALUATE(rand_dec, rand_string);
  MESSAGE('%1',rand_dec);
END;

I think this is going to be the best method, if I want a true random number, but I think I'll probably mostly just use Navision's RANDOM function. It did pass a few randomness tests that I threw at it.

I use random numbers for testing, mostly. But random numbers are very helpful in a lot of situations. How would I learn how to hook Navision up to a DLL or Excel's automation?

kapamarou · **Posted:** Fri May 11, 2012 12:49 am

It depends on the version you are using.

You can look at the Excel Buffer Table to see how to Interact with excel. Otherwise you could create a .NET dll or COM interface depending on the version.

kriki · **Posted:** Fri May 11, 2012 9:57 am

kapamarou wrote:

You can look at the Excel Buffer Table to see how to Interact with excel. Otherwise you could create a .NET dll or COM interface depending on the version.

I would advice against it because:
-you need Excel installed (and probably it must be the correct version)
-It is probably slower than RANDOM because you have to connect to .NET or COM.

After all, why do you need a random no. in NAV. Only to do some tests and for that the C/AL RANDOM is good enough.
If you need random numbers in a scientific way, you
1) need some black box (don't remember the name) that generates really random numbers using quantum fluctuations (some companies have created such a thing)
2) you're really using the wrong language/development environment for that.

Sog · **Posted:** Fri May 11, 2012 10:01 am

All in all, I think the topic is answered.
However, I am very curious in what business process a random number is needed.
Is it like a random discount? If you're lucky you'll receive a 100% discount?

Luc Van Dyck · **Posted:** Fri May 11, 2012 10:02 am

If you want to delve into the science of randomness, then look at this site: http://www.random.org/randomness/

David Singleton · **Posted:** Fri May 11, 2012 12:03 pm

Schrodinger's cat is long dead anyway, so why does it matter. :mrgreen:

Get a dog instead.

Sog · **Posted:** Fri May 11, 2012 1:46 pm

David Singleton wrote:

Schrodinger's cat is long dead anyway, so why does it matter. :mrgreen:

David, you can't state that as a fact if you havn't looked under the box :mrgreen:

(And how is this ontopic? I seem to have missed the link between Shrodingers cat and randomness)

David Singleton · **Posted:** Fri May 11, 2012 2:36 pm

But if I open the box then the randomness is gone. My gut feeling is that after all these decades trapped in the box that the kitten has by now starved or suffocated :cry:

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Can you get truly random numbers from Dynamics NAV?

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