Randomize function

[tiredofit]

Following from Rick Rothstein's comment here:

https://www.mrexcel.com/forum/excel-questions/747715-rnd-not-truly-random.html

he suggests, if I understood him correctly, that you should only ever have the randomize function once.


In that case, why not just put it in the Workbook_Open event?

Thanks

 

[Fluff]

I think he's saying that you should only run it once in any piece of code, rather than once per session.

 

[tiredofit]

I think he's saying that you should only run it once in any piece of code, rather than once per session.

So he's made a mistake?

 "The reason for the above suggestion is that the Randomize statement should only be run once per session... to do otherwise actually limits the number of random values the Rnd function can return."

 

[Fluff]

I wouldn't know, I was going by

Randomize should only be executed once per running of any code that uses the Rnd function call.

 

[shg]

It depends on what you're using Rnd() for.

Rnd has a very short cycle, so if you're doing something like generating rolls of a single di, you can accurately predict the entire sequence after watching a dozen or so results. If you were using it to generate alphanumeric passwords, one or two would do. If you want unpredictability, use Randomize often.

 

[tiredofit]

Thanks.

The main reason for using Rnd() is to generate as random a number as possible, so the more (Randomize) the merrier!

 

[shg]

Within reason. There are a lot of tests for randomness. I expect using Randomize on every call to Rnd would make the results fail some of those tests.

 

[shg]

You could instead use [=rand()]. It's much slower, but it has a pattern a million times longer.

 

[tiredofit]

Thanks

 

[Rick Rothstein]

Following from Rick Rothstein's comment here:

https://www.mrexcel.com/forum/excel-questions/747715-rnd-not-truly-random.html

he suggests, if I understood him correctly, that you should only ever have the randomize function once.


In that case, why not just put it in the Workbook_Open event?

It depends on what you're using Rnd() for.

Rnd has a very short cycle, so if you're doing something like generating rolls of a single di, you can accurately predict the entire sequence after watching a dozen or so results. If you were using it to generate alphanumeric passwords, one or two would do. If you want unpredictability, use Randomize often.

I posted the message at that link before what shg posted was pointed out to me. His suggestion to use [=rand()] (which he posted later in the thread) to obtain a random number is the way to go within VBA code.