Bug 512 – Adding UniformVariable::GetInteger and using it to fix bug in RealRandomStream::GetNext.

Bug 512 - Adding UniformVariable::GetInteger and using it to fix bug in RealRandomStream::GetNext.


Summary:	Adding UniformVariable::GetInteger and using it to fix bug in RealRandomStrea...

Status:	RESOLVED FIXED

Product:	ns-3
Classification:	Unclassified
Component:	core
Version:	ns-3-dev
Hardware:	All All

Importance:	P1 normal
Assigned To:	TimoB

URL:
Keywords:

Depends on:
Blocks:
	Show dependency tree / graph

Reported:	2009-02-25 07:37 EST by TimoB
Modified:	2009-03-04 13:14 EST (History)
CC List:	4 users (show)

See Also:

Attachments
UniformRandomGetInteger (2.40 KB, patch) 2009-02-25 07:37 EST, TimoB	Details \| Diff
fixed (1.89 KB, patch) 2009-02-25 07:43 EST, TimoB	Details \| Diff
Show Obsolete (1) Add an attachment (proposed patch, testcase, etc.)

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Description TimoB 2009-02-25 07:37:11 EST

RealRandomStream::GetNext() must return backoff values for DCF in the range [0..CW] with uniform probability distribution.

A quick test showed that this is not the case. See counts of some values pulled from GetNext(0,15):

0=4786 1=9297 2=9426 3=9365 4=9283 5=9335 6=9323 7=9365 8=9312 9=9400 10=9165 11=9482 12=9236 13=9178 14=9429 15=4618 16=0 17=0 

0 and 15 are only half as probable, because round yields 0 for 0-0.5 and 1 for 0.5-1.5.

Created UniformVariable::GetInteger(min,max).

The code works if UniformVariable::GetValue(min,max) never returns max. Is this absolutely positively the case?

All regressions using DCF are messed up.

Comment 1 TimoB 2009-02-25 07:37:48 EST

Created attachment 389 [details]
UniformRandomGetInteger

Comment 2 Mathieu Lacage 2009-02-25 07:39:37 EST

If you update the patch to work with the tip of ns-3-dev, this patch looks good to me.

Comment 3 TimoB 2009-02-25 07:43:53 EST

Created attachment 390 [details]
fixed

for tip

Comment 4 Mathieu Lacage 2009-02-25 07:45:47 EST

ok for me. raj, michele, can you ack this to fix the wifi regressions ?

Comment 5 Mathieu Lacage 2009-02-25 07:46:49 EST

adding michele as CC

Comment 6 Rajib Bhattacharjea 2009-02-26 12:48:45 EST

yeah looks good.  timo, ping me before you commit.

Comment 7 TimoB 2009-03-04 13:14:52 EST

fixed 4256:cc06d903ca09