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Re: [HACKERS] regressin failure on latest CVS

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Rocco Altier <RoccoA(at)Routescape(dot)com>
Cc: Michael Glaesemann <grzm(at)myrealbox(dot)com>,pgsql-patches(at)postgresql(dot)org, ohp(at)pyrenet(dot)fr
Subject: Re: [HACKERS] regressin failure on latest CVS
Date: 2005-07-23 19:35:35
Message-ID: 200507231935.j6NJZZF24034@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-patches
Rocco Altier wrote:
> That still does not fix it for me.
> 
> This patch is still using a computed float value (month_remainder and
> day_remainder), which is cauing the rounding errors.
> 
> There are now 6 machines on the build farm that are failing from the
> rounding:
> Wallaroo (OSX/G4), asp(AIX/powerpc), viper(FC3/x86_64),
> platypus(FBSD/amd64), kookaburra(AIX/powerpc), oriole(FC4/x86).
> 
> All of these are using enable-integer-datetimes.
> 
> What was wrong with the patch I sent?  I am doing as much as I can with
> integer math.

OK, new patch, please test.  Yea, I know your patch works, but we
usually keep at it until we have a clean, understood solution.  Thanks.

---------------------------------------------------------------------------

> 
> 	-rocco 
> 
> > -----Original Message-----
> > From: Bruce Momjian [mailto:pgman(at)candle(dot)pha(dot)pa(dot)us] 
> > Sent: Saturday, July 23, 2005 2:51 PM
> > To: Rocco Altier
> > Cc: Michael Glaesemann; pgsql-patches(at)postgresql(dot)org; ohp(at)pyrenet(dot)fr
> > Subject: Re: [HACKERS] regressin failure on latest CVS
> > 
> > 
> > 
> > Would you please try the attached patch and let me know if it 
> > fixes the
> > problem?  I avoided accumulating into a float8.
> > 
> > --------------------------------------------------------------
> > -------------
> > 
> > Rocco Altier wrote:
> > > This still does not fix the problem.
> > > 
> > > I had done my patch to try to mimic the way 8.0 had handled the math
> > > with the remainders, but to carry it over another bucket (day).
> > > 
> > > The problem that I see is that we are taking day_remainder and
> > > multiplying by USECS_PER_DAY.  Which is a double * int64, 
> > thus there is
> > > the precision loss there.
> > > 
> > > I think initial division by the factor can't be helped, but 
> > repeatedly
> > > doing more floating point math on with it is causing the 
> > rounding error.
> > > 
> > > Thanks,
> > > 	-rocco
> > > 
> > > > -----Original Message-----
> > > > From: Bruce Momjian [mailto:pgman(at)candle(dot)pha(dot)pa(dot)us] 
> > > > Sent: Saturday, July 23, 2005 10:54 AM
> > > > To: Rocco Altier
> > > > Cc: Michael Glaesemann; pgsql-patches(at)postgresql(dot)org; 
> > > > pgsql-hackers(at)postgresql(dot)org; ohp(at)pyrenet(dot)fr
> > > > Subject: Re: [HACKERS] regressin failure on latest CVS
> > > > 
> > > > 
> > > > Rocco Altier wrote:
> > > > > This patch fixes the interval regression on my AIX box 
> > > > (kookaburra) by
> > > > > only doing integer math on the interval, instead of 
> > > > float/double math.
> > > > > 
> > > > > I think this is the correct way to handle this, since it's 
> > > > an integer
> > > > > data type.
> > > > > 
> > > > > I don't know if it will fix Olivier's problem, since I 
> > > > wasn't able to
> > > > > reproduce it.
> > > > > 
> > > > 
> > > > I have changed the way I compute the remainder values --- 
> > instead of
> > > > using multiplication, I use division and then subtraction.  
> > > > This should
> > > > fix your rounding problem.  Looking at your fix, I don't see 
> > > > how adding
> > > > USECS changes things because the factor is already a float, 
> > > > but I think
> > > > the problem was more the way I was computing the remainders.
> > > > 
> > > > Patch attached --- let me know if it does not fix your problem.
> > > > 
> > > > --------------------------------------------------------------
> > >  
> > > 
> > > ---------------------------(end of 
> > broadcast)---------------------------
> > > TIP 2: Don't 'kill -9' the postmaster
> > > 
> > 
> > -- 
> >   Bruce Momjian                        |  http://candle.pha.pa.us
> >   pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
> >   +  If your life is a hard drive,     |  13 Roberts Road
> >   +  Christ can be your backup.        |  Newtown Square, 
> > Pennsylvania 19073
> > 
> 
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-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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Next:From: Bruce MomjianDate: 2005-07-23 19:53:09
Subject: Re: [HACKERS] regressin failure on latest CVS
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Subject: Re: [HACKERS] regressin failure on latest CVS

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