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AppGameKit Classic Chat / Generating a Random Float Number

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Funnell7
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Posted: 17th Jul 2012 18:26
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Hello, is it possible to generate a Random Float Number? From 1.0 to 3.0 for example? Random(1.0, 3.0) only returns integers...

I then thought perhaps taking a whole number and dividing it by 100 would work, but it doesn't. Is there a differnt command for a Random Float?

Many thanks!
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The Zoq2
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Posted: 17th Jul 2012 19:09
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Quote: "I then thought perhaps taking a whole number and dividing it by 100 would work, but it doesn't. Is there a differnt command for a Random Float?"


Are you sure about that, don't forget to store it as a float and not integer...
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Funnell7
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Posted: 17th Jul 2012 19:17 Edited at: 17th Jul 2012 19:19
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Hmmm... Ok, perhaps I am doing something wrong, I tried this;



This only ever returns 1.0 or 2.0 and nothing in between...

EDIT: Ah ha... I see what you mean now, they both have to be floats. I assumed you'd start with an int then divide that by 100, when in fact both need to be declared as floats. Perfect, thanks!
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The Zoq2
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Posted: 17th Jul 2012 19:22
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I had no idea the first one had to be a float

Glad you solved it though
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Impetus73
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Posted: 17th Jul 2012 19:51
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I think you could leave the first as an integer, if you use this: Float_RandomNumber = Int_RandomNumber / 100.0

100.0 = float. one of the numbers in the calculation has to be float to return a float, you can just let the 100 be a float by writing it as 100.0

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baxslash
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Posted: 17th Jul 2012 23:04
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You would be better either dividing by an explicit float ie. 100.0 not just 100 or alternatively multiply your integer by 0.01

I use this a lot and it works the multiplication way at least.


this.mess = abs(sin(times#))
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Funnell7
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Posted: 17th Jul 2012 23:24
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Thanks all, I ended up going with this which seems to work well...



Thanks again!
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Digital Awakening
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Posted: 17th Jul 2012 23:25
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Yeah, just make sure you have one float in there. Just like with DBP If you ever use all integers and need a float you can just throw in '*1.0'.

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Digital Awakening
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Posted: 17th Jul 2012 23:27
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What you need is: RandomTime = Random(100, 300) / 100.0

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BatVink
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Posted: 18th Jul 2012 00:46
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and bear in mind, multiplying by 0.01 is faster than dividing by 100.

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Marl
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Posted: 18th Jul 2012 02:40
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Quote: "and bear in mind, multiplying by 0.01 is faster than dividing by 100."

Is this from timing tests or is there a reference somewhere?

I've always been curious about the difference between multiply/divide vs binary shift for powers of two;

eg. 128/8 vs 128>>3

My tests seem to suggest multiply/divide is faster though historically it was always the opposite.
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baxslash
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Posted: 18th Jul 2012 13:36
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RandomTime# = Random(100, 300)* 0.01 is the quickest yes (on Windows at least). Not sure about historically and perhaps this might differ depending on the platform?

Either way that's the way I use it more often than not. I only divide by a float if it's not being used every loop and it makes the code easier to understand.


this.mess = abs(sin(times#))
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Dar13
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Posted: 18th Jul 2012 22:54
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Quote: "Is this from timing tests or is there a reference somewhere?"

I do believe this comes from there being less instructions required to do a multiplication in assembly versus division.
More detailed answers here.

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Kevin Picone
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Posted: 19th Jul 2012 07:47
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The raw instruction timings aren't really relevant since AppGameKit BASIC programs are running on VM. So the bulk of the mult/division operation codes execution time really in VM's opcode fetch, rather than the operation.


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