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Re: [ANN] The STON Specification, Cog speed, and namespaces/modules

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Shaping1

Re: [ANN] The STON Specification, Cog speed, and namespaces/modules

Hi Eliot.

Pharo (& Squeak & Cuis) Float subclass BoxedFloat64 maps exactly to VW's Double. In 64-bit SmallFloat64 maps exactly to SmallDouble. But I wonder whether there is any issue here. STON would use the print strings for (PSC) Float / (VW) Double, and so deseerialization on Pharo would automatically produce the right class. Going in the other direction might need some help. APF needs support in PSC before one can port, but are representable as suitably-sized word arrays.

There is no support for __float128 anywhere in the VM (e.g. not even in the FFI) on PSC as yet.

I see Pharo’s WordArray. I’ll work on an APF for Pharo, as time permits. I’m using APFs in VW in the 300-bit range, and want to reduce the needed precision to 64 bits, to save space and time on large (5 million+) scalar time-series, both on the heap and during BOSSing (25 m save-time now). The problem is not so much an issue for the JulianDayNumber (JDN)-precision, which is adequate in this app at 14 to 15 digits (even though my JDN class subclasses APF, for now). Other calculations need the more extreme precision. I think I can make 128-bit floats work, and would really like to see a small, fast, boxed 128-bit float implementation in Pharo or VW. The APFs are big and slow. Where in the queue of planned improvements to Pharo does such a task lie? I suspect it’s not a very popular item.

Broadening the issue somewhat, I’m trying to find as many good reasons as possible to justify the work needed to port all my VW stuff to Pharo.

I’ve seen the references to Cog’s speed and coming speed-up. Are there recent (say, in the last year) benchmarks comparing VW and Pharo? Any details here would be very much appreciated.

Having no namespaces in Pharo is, I think, the biggest impediment. I prefer not to prefix class names, but there may be fewer name-collisions than I suppose--maybe none. Still, I need to know how VW and Pharo classes map in order to place overrides and extensions correctly. Besides the mentioned float-class mappings is there a reference on this?

Object allSubclasses

in Pharo 7 64-bit, produces 14946 classes. Pharo is a little bigger than it used to be.

I suppose I don’t need to check all unloaded packages because all classes in each of those will have the same unique prefix. Is that correct? Or, I could just load every package I can find, before I check names. But that little experiment has never gone well in the past.

Is the Pharo-with-namespaces issue dead or merely suspended, awaiting a more fitting idea than what VW currently offers?

Shaping

On Tue, Nov 6, 2018 at 12:56 AM Shaping <[hidden email]> wrote:

STON is able to serialise Pharo’s Floats, what do you mean by double ?

Floating-point numbers in IEEE 64-bit format, 14 or 15 significant digits, with a range between =10^307 and 10^307.

Additionally, I recently asked Sven if t would be possible to store ScaledDecimals (I think it implements what you call ArbitraryPrecisionFloats) without loss of precision.

I’m referring to VW’s Double (and SmallDouble in 64-bit engines/images). APFs are binary representations that can be arbitrarily large, using Integers (LargePositiveIntegers for example) to model the bits of the mantissa.

Before, because STON extends JSON, it was storing all kind of numbers either as float or integer.

Now, thanks to Sven, STON stores ScaledDecimals correctly (without loss of precision through serialisation as float, what was done before).

But I do not know if this change is integrated in recent images yet.

…..

Number subclass: #Float
                instanceVariableNames: ''
                classVariableNames: 'E Epsilon Halfpi Infinity Ln10 Ln2 MaxVal MaxValLn MinValLogBase2 NaN NegativeInfinity NegativeZero Pi RadiansPerDegree Sqrt2 ThreePi Twopi'
                poolDictionaries: ''
                category: 'Kernel-Numbers'

My instances represent IEEE-754 floating-point double-precision numbers. They have about 16 digits of accuracy and their range is between plus and minus 10^307. Some valid examples are:

                8.0 13.3 0.3 2.5e6 1.27e-30 1.27e-31 -12.987654e12
….

I see that Pharo’s Float is VW’s Double.   So then I just need to be able to serialize APF.

….
FIFloatType subclass: #FFIFloat128
                instanceVariableNames: ''
                classVariableNames: ''
                poolDictionaries: ''
                category: 'UnifiedFFI-Types'

I'm a 128bits (cuadruple precision) float.
It is usually not used, but some compiler modes support it (__float128 in gcc)

THIS IS NOT YET SUPPORTED
….

The class above is also from the Pharo 7 image. This is the largest of the c-type FFIFloats. Any Float classes of this size and larger for the Smalltalk heap on 64-bit Pharo?

Cheers,

Shaping

Le 6 nov. 2018 à 06:58, Shaping <[hidden email]> a écrit :

(Having domain problems recently. Please excuse this posting if you have
seen it twice. I've not seen it appear yet on the list.)

Can STON be extended to handle Doubles and ArbitraryPrecisionFloats?

Shaping

-----Original Message-----
From: Pharo-dev [[hidden email]] On Behalf Of
David T. Lewis
Sent: Wednesday, October 31, 2018 14:58
To: Pharo Development List <[hidden email]>
Subject: Re: [Pharo-dev] [ANN] The STON Specification

This is very clear and well written.

Dave

Hi,

Since there can never be enough documentation I finally took some time
to write a more formal description of STON as a data format.

https://github.com/svenvc/ston/blob/master/ston-spec.md

The idea is to let this stabilise a bit and to then update the two
other documents describing STON, where necessary:

https://github.com/svenvc/ston/blob/master/ston-paper.md

https://ci.inria.fr/pharo-contribution/job/EnterprisePharoBook/lastSuc
cessfulBuild/artifact/book-result/STON/STON.html

Also, the latest changes in STON have to make their way to the Pharo
image as well.

https://github.com/svenvc/ston

All feedback is welcome.

Sven

--
Sven Van Caekenberghe
Proudly supporting Pharo
http://pharo.org
http://association.pharo.org
http://consortium.pharo.org

_,,,^..^,,,_

best, Eliot