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Re: Re: Help with a possible bug
*To*: mathgroup at smc.vnet.net
*Subject*: [mg98983] Re: [mg98943] Re: Help with a possible bug
*From*: peter <plindsay.0 at gmail.com>
*Date*: Thu, 23 Apr 2009 06:43:01 -0400 (EDT)
*References*: <gsivea$9bt$1@smc.vnet.net> <gsk2gp$nu3$1@smc.vnet.net>
"7.0 for Mac OS X x86 (32-bit) (February 18, 2009)"
{691894176, 691894176, 691894176, 691894176, 691894176, 691894176,
691894176, \
691894176, 691894176, 691894176, 691894176, 691894176, 691894176,\
2009/4/22 Raffy <raffy at mac.com>
> On Apr 21, 2:09 am, Bob F <deepyog... at gmail.com> wrote:
> > On Apr 20, 5:11 pm, M8R-lj1... at mailinator.com wrote:
> >
> >
> >
> >
> >
> > > At work we seem to have stumbled on a strange bug between Table and
> > > Part. We can reproduce the bug on differently configured Mac and
> > > Linux boxes. I tried Wolfram support, but they claim they cannot
> > > reproduce the bug. So I was hoping someone could try it out and
> > > report their results. Thanks in advance to all volunteers.
> >
> > > For us, the bug is new in 7.0.1. It does not show up in version 6.
> > > To reproduce it, fill up a 17 x 267 matrix with 3s. Compute the sum
> > > of some of the columns and you get the result 51 (17 x 3). But if on=
> e
> > > computes the sum for the last few columns, the result is completely
> > > off. The bug seems to arise from the interaction of optimizations =
> i=
> > n
> > > Table and the use of All inside of Part.
> >
> > > ------------ code
> >
> > > mat = Table[3, {i, 1, 17}, {j, 1, 267}];
> >
> > > sum = Table[Total[mat[[All, j]]], {j, 1, 249}]
> >
> > > sum1 = Table[Total[mat[[All, j]]], {j, 1, 252}];
> > > sum2 = Table[Total[mat[[All, j]]], {j, 1, 252}]
> >
> > > ------------ end code
> >
> > > If you look at sum1, it will be correct on a fresh copy of the
> > > Kernel. The problem only arise from the second time on.
> >
> > > Thanks,
> >
> > > Papin
> >
> > > Email: ImportString["cGFwaW5AY294Lm5ldA==", "Base64"]
> >
> > How bizarre!! On my Mac with version 7.0.1 every sum for the last 18
> > columns is bogus, and it appears that the bogus values keep changing
> > in some sort of random way. For example if you tried
> >
> > mat = Table[3, {i, 1, 17}, {j, 1, 267}];
> > Manipulate[
> > sum = Table[Total[mat[[All, jj]]], {jj, 1, mm}], {mm, 1, 267, 1}]
> >
> > everything is OK up thru 249th column (and even thru the 267th the
> > first time on a fresh kernel just like you described), then as soon as
> > you select any other of the 250th thru 267th columns - they total goes
> > squirrely from then on for all subsequent TOTAL's that are calculated,
> > and changes every time you look at any of the last 18 (even looking at
> > the same column total the numbers are different, ie look at column
> > 267, then 266, then 267 again and the numbers are different from the
> > first time you looked), so there is apparently some sort of random
> > gibberish it is picking up when the totals are calculated.
> >
> > Try sending Wolfram the Manipulate command and it's trivial to
> > reproduce on a Mac -- make sure you stay on the phone with them while
> > they try it on a Mac.
> >
> > To make it even more obvious, change the starting index on the
> > Manipulate to 248 and start "playing" the manipulate and watch it go
> > bonkers. The numbers seem to always be 9 digits and are between the
> > upper 200 millions and the middle to upper 300 millions in magnitude,
> > but didn't seem to get much different even after letting the
> > Manipulate play for quite a while at the highest "speed".
> >
> > Let us know what they say.
> >
> > -Bob
>
> It is definitely a bug with auto-compilation.
>
> SetSystemOptions["CompileOptions" -> "TableCompileLength" -> Infinity]
> will restore expected operation.
>
>
--
Peter Lindsay
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