[OpenFL Cpp] simple pseudorandom algo works differently with/without "-debug"

[Rezmason]

Hey folks! I've tried writing a simple function to generate sorta random Floats between 0 and 1:

function lgm(n:UInt):Void->Float {
return function() {
n = (n * 0x41A7) % 0x7FFFFFFF;

return n / 0x7FFFFFFF;

}

}

I'm using this function in an OpenFL project that I'm compiling for the Mac. When I compile the project with the "-debug" flag, this function spits out numbers between 0 and 1, as expected. But when I compile the project without the "-debug" flag, two thirds of the numbers are between 0 and 1, and one third of the numbers are between 1 and 2!

Could someone explain to me what's going on behind the scenes here? The C++ file generated for the class this function sits in looks the exact same for both builds, so, I'm at a loss.

[Rezmason]

...That looks nothing like code, does it. I'll try again:

[Rezmason]

Ah, this seems to fix it! I've stored the literals in variables of type UInt:

function lgm(n:UInt):Void->Float {

    var a:UInt = 0x41A7;

    var div:UInt = 0x7FFFFFFF;

    return function() {

        n = (n * a) % div;

        return n / div;

    }

}

[Hugh]

Just a comment - not saying you are wrong - but I would think the "&" operator would be more normal than the "%" operator here (and then divide by 0x8000000)

Hugh

[Rezmason]

On Sunday, June 22, 2014 9:37:48 PM UTC-7, Hugh wrote:

Just a comment - not saying you are wrong - but I would think the "&" operator would be more normal than the "%" operator here (and then divide by 0x8000000)

Hugh

Noted! I haven't even checked yet whether my algo generates the same values from one platform to the next- it's a placeholder, until then. :-)