Linepicks - do they give same result on all PCs

Blitz3D Forums/Blitz3D Programming/Linepicks - do they give same result on all PCs

Simple question:

If I have the same mesh being used on two separate PCs, and perform a linepick against it using the same parameters on both PCs will it return the same values for Pickedy(),pickedx(),pickedz()?

Or to put it another way - do floating point calculations give the same result on different processors?

podperson

They should (plus or minus the infamous "pentium bug" ;) )

Bot Builder

Put up some test code using large numbers (to allow for more probability of floating point rounding issues).

Then have varius people test it. I think that most computers will return the same result but it shouldn't be relied upon.

charliex

with floating point you don't test for equality, you test with an epsilon value, so instead of saying is a=b (where a and b are floats) you'd do (a-b)<0.5 where the 0.5 is a value your games engine works with. That way you'll avoid accuracy problems.

Matty

Could people run the code below for me and send me the file as an attachment in an email to gezeder@...

Thanks

myfile=writefile("test.txt")
a#=5.0
b#=2.0
c#=3.0
for i=1 to 100
writefloat myfile,float(i)*sqr(a#*a#/float(i)+b#*b#+c#*c#*float(i))
writefloat myfile,float(i)*sin(float(i))
next
closefile myfile

Bot Builder

I'll just give yah the numbers

Oh, and if others just want to pust them:

a#=5.0
b#=2.0
c#=3.0
For i=1 To 100
 DebugLog Float(i)*Sqr(a#*a#/Float(i)+b#*b#+c#*c#*Float(i))
 DebugLog Float(i)*Sin(Float(i))
Next
Stop ;so you can copy/paste

Nilium

My results.

Beaker

Rhyolite

How do I put this in one of those snazzy table thingy mi jigs???

EDIT : Cheers :o)

3Ghz Pentium

Genexi2

#10

Hmmm.......the results seem to be pretty well the same (cant be arsed to do a full for-number check between sources...or let alone code one up, but they look pretty-well the same to me anyway.

Oh, btw, on an AMD Athlon XP1800+ processor here.

(psst, Rhyolite, look over here)

Rottbott

#11

For future compatibility, I wouldn't rely on this if I were you.

Matty

#12

I would prefer to receive the numbers not in string format. I have found that Blitz does not return the same values on various pcs when they are converted to strings. So if I could just have the test.txt file and then do a file comparison on the bytes present in the file that would be appreciated.

Rob

#13