[Vm-dev] cosine broken in all MacOSX squeak VM ???

[David T. Lewis]

Nicholas,

If you have a chance, could you try this on an interpreter VM and see if
you get the same results?

   http://squeakvm.org/unix/release/Squeak-4.10.2.2614-darwin10.8.0_i386.tar.gz

This does not sound like something that should be specific to Cog so I am
expecting you would see the same issue on both VMs. If so, we can take
a look at the plugin and see what is going on.

Dave


On Wed, Dec 19, 2012 at 03:33:24PM -0800, Eliot Miranda wrote:
>  
> Hi Nicholas,
> 
>     I'll take a look as soon as time allows.  I'm debugging a Newspeak
> issue right now.
> 
> 
> On Wed, Dec 19, 2012 at 1:34 PM, Nicolas Cellier <
> nicolas.cellier.aka.nice at gmail.com> wrote:
> 
> >
> > I just tried this a latest cog:
> >
> > (1 to: 300) collect: [:i | (10.0 raisedTo: i) sin squared + (10.0
> > raisedTo: i) cos squared - 1 / Float epsilon]
> > -> #(1.0 -21.0 -215.0 1951.0 -825.0 164322.0 2.991826e6 ...
> >
> > It sounds like incredibly high errors so soon...
> >
> > The sine is OK:
> > (1 to: 300) collect: [:i | (10.0 raisedTo: i) sin - ((10.0 raisedTo:
> > i) asArbitraryPrecisionFloatNumBits: 53) sin asFloat / ((10.0
> > raisedTo: i) asArbitraryPrecisionFloatNumBits: 53) sin asFloat ulp]
> > ->  #(-1.0 0.0 1.0 0.0 0.0 0.0 ...
> >
> > This is due to cosine:
> > (1 to: 300) collect: [:i | (10.0 raisedTo: i) cos - ((10.0 raisedTo:
> > i) asArbitraryPrecisionFloatNumBits: 53) cos asFloat / ((10.0
> > raisedTo: i) asArbitraryPrecisionFloatNumBits: 53) cos asFloat ulp]
> > -> #(-1.0 -24.0 -383.0 -2049.0 825.0 175417.0 -3.297612e6 ...
> >
> > Though, MacOSX math library is very robust and accurate even for Float
> > fmax, this one works well:
> >
> > #include <stdio.h>
> > #include <math.h>
> > int main()
> > {
> >     int i;
> >     double d,y;
> >     for(i=1;i<301;i++) {
> >         d=pow(10.0,i);
> >         y=(cos(d)*cos(d)+sin(d)*sin(d)-1)/ldexp(1.0,-52);
> >         printf("i=%d y=%.17f\n",i,y);
> >     }
> >     return 0;
> > }
> >
> > $ gcc --version
> > i686-apple-darwin10-gcc-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5666) (dot 3)
> > Copyright (C) 2007 Free Software Foundation, Inc.
> >
> > It sounds like sin is taken from one accurate library while cos is
> > taken from an inacurrate one !!!
> > For example it sounds like cos might well be using broken x86 fcos
> > How can it be so?
> > Can someone explain ?
> >
> > Virtual Machine
> > ---------------
> > /Users/nicolas/Smalltalk/Squeak/Cog.app/Contents/MacOS/Croquet
> > Croquet Closure Cog VM [CoInterpreter VMMaker.oscog-eem.238] Croquet
> > Cog 4.0.2637
> > Mac OS X built on Dec 17 2012 19:54:57 Compiler: 4.2.1 (Apple Inc.
> > build 5666) (dot 3)
> > platform sources revision VM: r2637
> > http://www.squeakvm.org/svn/squeak/branches/Cog Plugins: r2545
> > http://squeakvm.org/svn/squeak/trunk/platforms/Cross/plugins
> > CoInterpreter VMMaker.oscog-eem.238 uuid:
> > a3d10eab-6079-4c91-99f6-3dcf58d1446f Dec 17 2012
> > StackToRegisterMappingCogit VMMaker.oscog-eem.234 uuid:
> > 66acafd1-cad0-4f20-b786-ab8f48201d82 Dec 17 2012
> >
> > Loaded VM Modules
> > -----------------
> > B2DPlugin VMMaker.oscog-eem.235 (i)
> > BitBltPlugin VMMaker.oscog-eem.235 (i)
> > DropPlugin VMMaker.oscog-eem.235 (i)
> > FilePlugin VMMaker.oscog-eem.235 (i)
> > FloatArrayPlugin VMMaker.oscog-eem.235 (e)
> > InternetConfigPlugin VMMaker.oscog-eem.235 (i)
> > LargeIntegers v1.5 VMMaker.oscog-eem.235 (i)
> > Matrix2x3Plugin VMMaker.oscog-eem.235 (i)
> > MiscPrimitivePlugin VMMaker.oscog-eem.235 (i)
> > SecurityPlugin VMMaker.oscog-eem.235 (i)
> > SocketPlugin VMMaker.oscog-eem.235 (i)
> > ZipPlugin VMMaker.oscog-eem.235 (i)
> > Same results with old VM
> >
> >
> > Same result with old 4.2.5 VM !!!
> >
> > Virtual Machine
> > ---------------
> > /Users/nicolas/Smalltalk/Squeak/Squeak
> > 4.2.5beta1U.app/Contents/MacOS/Squeak VM Opt
> > Squeak4.1 of 17 April 2010 [latest update: #9957] Squeak VM 4.2.5b1
> > Mac Carbon 4.2.5b1 15-Jun-10 >85D9C693-2A2A-4C33-B05C-C20B2A63B166<
> > VMMaker versionString 4.2.4
> >
> > Loaded VM Modules
> > -----------------
> > B2DPlugin 15 June 2010 (i)
> > BitBltPlugin 15 June 2010 (i)
> > DropPlugin 15 June 2010 (i)
> > FilePlugin 15 June 2010 (i)
> > FloatArrayPlugin 15 June 2010 (i)
> > InternetConfigPlugin 15 June 2010 (i)
> > LargeIntegers v1.5 15 June 2010 (i)
> > Matrix2x3Plugin 15 June 2010 (i)
> > MiscPrimitivePlugin 15 June 2010 (i)
> > SecurityPlugin 15 June 2010 (i)
> > SocketPlugin 15 June 2010 (i)
> > ZipPlugin 15 June 2010 (i)
> >
> 
> 
> 
> -- 
> best,
> Eliot