RAND function

Blitz3D Forums/Blitz3D Programming/RAND function

Gerard

(Posted 2010) [#1]

hello !

Is one of you knowing with which algorithm is programmed the "rand" function in Blitz3D ?

I would like to know it to make the same function in an old program in GFA-Basic, and compar results with this program rewritten in Blitz3d .

Thank you in advance for any answer !

Cordially
Gerard

stanrol

(Posted 2010) [#2]

Likely passthrough to C++ rand()l.

Krischan

(Posted 2010) [#3]

You could try this way (using pseudorandom numbers):

Graphics 512,256,32,2

Global seed%=42

.again

SeedRnd seed

SetBuffer BackBuffer()
LockBuffer BackBuffer()

ms1=MilliSecs()
For y=0 To 255
	For x=0 To 255
		h=MyRAND(255)
		rgb=h*$10000+h*$100+h
		WritePixelFast x,y,rgb
	Next
Next
ms1=MilliSecs()-ms1

ms2=MilliSecs()
For y=0 To 255
	For x=0 To 255
		h=Rand(0,255)
		rgb=h*$10000+h*$100+h
		WritePixelFast 256+x,y,rgb
	Next
Next
ms2=MilliSecs()-ms2

UnlockBuffer BackBuffer()

Color 0,0,0
Rect 0,0,512,12,1

Color 255,0,0
Line 256,0,256,256

Text 128,0,"MyRAND Function ["+ms1+"]",1
Text 384,0,"Blitz RND Function ["+ms2+"]",1

Flip

WaitKey
If Not KeyHit(1) Goto again

End


Function MyRAND%(max%,min%=0)
	
	Local tmp%
	If min>max Then tmp=min : min=max : max=tmp
	
	Local x%=seed : seed=seed+57
	x=x Shl (13^x)
	Return Normalize((((x*(x*x*15731+789221)+1376312589) And $7fffffff)/1073741824.0),0,2,min,max)
	
End Function

Function Normalize#(v#=128.0,vmin#=0.0,vmax#=255.0,nmin#=0.0,nmax#=1.0)
	
	Return ((v-vmin)/(vmax-vmin))*(nmax-nmin)+nmin
	
End Function

Zethrax

(Posted 2010) [#4]

Likely passthrough to C++ rand()l.

Very probably. I recall Mark Sibly mentioning on another forum that he made extensive use of the C++ STL in coding Blitz3D, and I doubt that he'd try to reinvent the wheel when perfectly good existing solutions were available.