Random generates two identical numbers in different time

[DrOtosclerosi]

Hi all!

In a software I'm developing and mantaining for my company I'm generating a random between 1 and 65535 (float included) to create a file that must be unique in each instance.

The file is generated when a work report is saved, and put in a folder with a reference in the work report xml file.

Long story short, last week happened twice that two work report xml files pointed to the same random file (reports created even in different days)!

By now I changed the naming of the random file with:

Random(1, 64, 1) & @MDAY & "." & @MON & "." & "." & @HOUR & "." & @MIN & "." & @SEC & "." & @MSEC

So I solved the problem but...how could this happen? Just bad luck or misuse of random()?

Is there any way to generate a seed?

This is the part of the code generating the random:

Global $MagRand = Random(1, 65535)

And seems very straightforward.

[RTFC]

Please study the help file before you post

[DrOtosclerosi]

Just now, RTFC said:

Please study the help file before you post

Thanks, I've missed that part even after googling.

[RTFC]

No need to google. In the AutoIt Help file's topic Random, under heading "Related," there's a direct link to SRandom().

[DrOtosclerosi]

Ok thank you again

I must have missed that

[BugFix]

If it must unique you can use 

_WinAPI_CreateGUID()

.

[DrOtosclerosi]

26 minutes ago, BugFix said:

If it must unique you can use 

_WinAPI_CreateGUID()

.I don't know GUID very much, is GUID a random number?

 

[TheXman]

6 hours ago, DrOtosclerosi said:

So I solved the problem but...how could this happen? Just bad luck or misuse of random()?

How could this happen?  It happened because you obviously do not understand what the word random means or, at least, the difference between random and unique.  Randomness has absolutely nothing to do with uniqueness.  A random number generator can generate the same number several times in a row and it could still be a randomly generated sequence.

The easiest way to have fixed your original code would have been to check if the randomly generated number (file name) exists, and if so, generate another random number until the generate number (file name) doesn't exist. 

The _TempFile() function generates a file name that is guaranteed not to exist yet.  Maybe taking a look at the code behind the function will help you understand how it is done.  Better yet, you can just use the _TempFile() function and be done with it.  You obviously do not have any special criteria for the file name itself if you were just using a number between 1 and 65535.  So it should meet your needs.

Edited November 11, 2019 by TheXman

[iamtheky]

[DrOtosclerosi]

23 hours ago, TheXman said:

How could this happen?  It happened because you obviously do not understand what the word random means or, at least, the difference between random and unique.  Randomness has absolutely nothing to do with uniqueness.  A random number generator can generate the same number several times in a row and it could still be a randomly generated sequence.

The easiest way to have fixed your original code would have been to check if the randomly generated number (file name) exists, and if so, generate another random number until the generate number (file name) doesn't exist. 

The _TempFile() function generates a file name that is guaranteed not to exist yet.  Maybe taking a look at the code behind the function will help you understand how it is done.  Better yet, you can just use the _TempFile() function and be done with it.  You obviously do not have any special criteria for the file name itself if you were just using a number between 1 and 65535.  So it should meet your needs.

Thanks a lot! I'm looking at _TempFile() and seems to be perfect!