June 2021 - Pharo-users - lists.pharo.org

Re: Rounding in Floats

by Esteban Maringolo

On Wed, Jun 16, 2021 at 10:49 AM Richard O'Keefe <raoknz(a)gmail.com> wrote: > The problem is that while it is possible to read the ANSI Smalltalk standard as requiring ScaledDecimals to be fixed point numbers (which are a kind of exact rational number of the form x * 10**y, x and y integers), in Squeak and Pharo ScaledDecimal numbers are NOT fixed-point numbers. They are unlimited rational numbers with the scale being used for printing purposes only. This creates enormous confusion and I really don't see any point in Squeak/Pharo ScaledDecimal existing at all. I only used decimals in other platforms, and only for accounting purposes, but to me if two scaled decimals print the same but answer false to #= then something is wrong conceptually. I can identify the issue, but the reasoning behind how it works, or even more, how to fix it, is above my level. > There *is* point in having fixed-point decimal numbers as they are a perfect match for SQL data bases and several programming languages. That's the only use I gave it. So if we divided 10.0s1 / 3 ended up with 3.3s1 each, and we had to calculate the rounding errors (0.1s1 in this case) to make all balance. > I've now located a PDF of the USGA Rules of Handicapping. Wow. 128 pages. That's just USGA, there is a "World System" but each "region" or local federation does a variation of the "world system". So Belgium does one thing, Australia another one, Argentina another one, England decided to only take one part... standards, they call it :-) I Implemented a couple of them. > And with all that they couldn't explain the calculations precisely. Try to ask one federation how they calculate the PCC, and they won't tell you, it's like the coca-cola formula. > Rounding > arrives in more than one place. For example you might have to average the > best 1-8 of the last (as many as are available up to 20) scores and then round > to one decimal, but it is not stated how ties are to be broken (which can arise > for the best 2, 4, 6, or 8). In this computation, the tie doesn't matter, because you start with an _already rounded_ number (called a "differential"), so it doesn't matter if you choose 11.4 from the 5th or 11.4 from the 19th. The rounding happens at the very end and determines a new rounded (to one decimal) number that's going to be used in other formulas (like the one that re-kicked this thread). The ties in competitions are solved differently. In real tournaments by playoff, or in amateur tournaments either by playoff or by a hole by hole comparison. If that even happens[*], there is the option to toss a coin to untie it. [*] In +400 tournaments managed by my software (involving ~15000 scorecards), that never happened. So to wrap up and bring it back to the topic, a proper ScaledDecimal implementation would help me storing the numbers as such guaranteeing no floating point funny thing happens, but since there is no such thing, I'll rather build the scaled decimals manually (e.g. ScaledDecimal fromFraction: 67/10) or not use scaled decimals and try to use the Fractions directly wherever possible. It's always good to learn new things.

June 16, 2021

Re: Problem installing 9.0 on MacMini M1

by Clacton Server

I am nearly there. I sorted out the curl/wget business and managed to get the new VM. I have installed it and everything is very quick so I am pleased. However there are two things I am not sure of. 1. Once I close this down, I am not confident of finding it again (smile). 2. I am back with the Path issue that I mentioned a while ago. Instead of (FileSystem disk workingDirectory) being set at the Pharo level it is now set at the very top of the tree. Is this something that I am going to have to live with our can I reconfigure the startup to make it as it was? David > On 16 Jun 2021, at 12:56, David Pennington <david(a)totallyobjects.com> wrote: > > I transferred both of my images ( 8 and 9) across and put them in the images directory of a new Pharo Launcher. I now have 9.0 working on the Mac mini but it is still telling me that my VM is out of date. I have opened the VM window and updated both the 8 and 9 vm but I still get the message. I am not convinced that I have an M1 VM. > > How do I sort this. I am nearly there. > >> On 15 Jun 2021, at 18:44, Tim Mackinnon <tim(a)testit.works <mailto:tim@testit.works>> wrote: >> >> Worth saying that while Brew is handy on a mac (and avoid installing it as a sudo user) - you shouldn't need it do anything with Pharo either with with the launcher (graphical) or via the console (command line). >> >> Its worth checking you have properly read the download instructions on pharo.org <http://pharo.org/> - for command line it does say use "curl" and "wget if curl not available". >> >> For your pharo damaged question - have you tried just creating a fresh directory, cd'ing into it and then running the command line instructions for a fresh install. You can then make sure sure pharo works correctly command line - and if so, this is then possibly a 32 vs 64 bit image difference. You could investigate this - or simply create a new image and install your code into it as a fresh install - which might be better anyway, while your getting things sorted. >> >> Others may have more tips for you. >> >> Tim >> >> On Tue, 15 Jun 2021, at 5:58 PM, Rob Sayers wrote: >>> Hi, I can't help with the Pharo specific issue, but for installing brew, you can find the directions here: https://brew.sh/ <https://brew.sh/> >>> >>> On Tue, Jun 15, 2021 at 10:16 AM David Pennington <david(a)totallyobjects.com <mailto:david@totallyobjects.com>> wrote: >>> Hi everyone. It is your favourite newbie speaking :-) >>> >>> I have now got a new M1 MacMini which I want to configure up as a server for my Seaside apps. >>> >>> So far, I have found that the Mac mini doesnât have wget or brew installed! I have sorted wget but not brew. >>> >>> Secondly, I have transferred all of my 9.0 stuff across but when I try and execute both paharo-ui or pharo (as terminal scripts) they both fail as they say that the âPaharoâ is damaged and canât be opened. You should move it to the bin. >>> >>> I can open Pharo 9.0 directly but it tells me that the VM is too old for this image. >>> >>> Can anyone help me please? (In words that I can understand:-) >>> >>> David >>> >>> >>> -- >>> Rob Sayers >>> www.robsayers.com <http://www.robsayers.com/>

June 16, 2021

Re: Rounding in Floats

by Konrad Hinsen

On 16/06/2021 15:52, Sven Van Caekenberghe wrote: > I am also a bit intrigued by this. Like you said: several other programming languages (I tried a couple of Common Lisp and Scheme implementations) do the same as Pharo, but handheld calculators, normal and scientific, do not. Handheld calculators use decimal floats, not binary floats. That doesn't remove rounding issues, but it makes conversion to and from print representations loss-free. Konrad

June 16, 2021

Re: How to get dimensions (extent) of a SpPresenter

by kmo

Many thanks esteban - works fine now in Gtk -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

June 16, 2021

Re: Rounding in Floats

by Sven Van Caekenberghe

I am also a bit intrigued by this. Like you said: several other programming languages (I tried a couple of Common Lisp and Scheme implementations) do the same as Pharo, but handheld calculators, normal and scientific, do not. I think that going for 1/10 fractions/precision is not going to help: you got a division by 113 in your formula [https://en.wikipedia.org/wiki/Handicap_(golf)] this will give smaller fractions. The problem is not the calculation (modern 64-bit floats as in Pharo are plenty accurate), it is how you handle results. You should just round it correctly and be done with it. Note that a roundTo: 0.00000000000001. (1e-14) still gives 4.5 it is only one step further that you hit the limit and get the ugly but correct result. I assume that most calculators always use a printing precision that is lower than their internal precision, hence they hide this reality. When computing with money, you would be inclined to put everything in cents (because you cannot divide them further). But once you start computing percentage discounts or taxes, you again get problems. At each of those steps you must make sure that no cents are lost. > On 16 Jun 2021, at 15:19, Esteban Maringolo <emaringolo(a)gmail.com> wrote: > > On Wed, Jun 16, 2021 at 9:13 AM Konrad Hinsen > <konrad.hinsen(a)fastmail.net> wrote: >> >> On 15/06/2021 16:05, Esteban Maringolo wrote: >>> And in this particular case, it might cause issues, since the "full >>> precision" (whatever that means) must be retained when using such a >>> number to derive another one. >> >> To me, "full precision" means "no precision is ever lost in arithmetic >> operations". If that's what you need, your choices are >> >> 1) Integers >> >> 2) Rational numbers (fractions) > >> Pharo has 1) and 2). > > Yeap, I'll switch to 2. > > What I'm not totally convinced of is whether to store numbers as > integers (knowing beforehand the decimal precision, and converting it > to fractions when read back) or if to store them as scaled decimals > (which internally hold a fraction). > > Thanks!

June 16, 2021

Re: Rounding in Floats

by Richard O'Keefe

The problem is that while it is possible to read the ANSI Smalltalk standard as requiring ScaledDecimals to be fixed point numbers (which are a kind of exact rational number of the form x * 10**y, x and y integers), in Squeak and Pharo ScaledDecimal numbers are NOT fixed-point numbers. They are unlimited rational numbers with the scale being used for printing purposes only. This creates enormous confusion and I really don't see any point in Squeak/Pharo ScaledDecimal existing at all. There *is* point in having fixed-point decimal numbers as they are a perfect match for SQL data bases and several programming languages. I've now located a PDF of the USGA Rules of Handicapping. Wow. 128 pages. And with all that they couldn't explain the calculations precisely. Rounding arrives in more than one place. For example you might have to average the best 1-8 of the last (as many as are available up to 20) scores and then round to one decimal, but it is not stated how ties are to be broken (which can arise for the best 2, 4, 6, or 8). It is probably safe to assume rounding out. Number>>roundOut ^self negative ifTrue: [((self * 2 - 1) / 2) ceiling] ifFalse: [((self * 2 + 1) / 2) floor] On Wed, 16 Jun 2021 at 02:06, Esteban Maringolo <emaringolo(a)gmail.com> wrote: > Well... fixed point numbers (aka ScaledDecimals) had their issues as well. > > And in this particular case, it might cause issues, since the "full > precision" (whatever that means) must be retained when using such a > number to derive another one. > > E.g. in my case: > ch := 6.7 + (32.8 - 35). "course handicap" > allowance := 0.85. "85%" > ph := (ch * allowance) roundedHandicap. "playing handicap" > > The #roundedHandicap is like #rounded but rounds -0.5 towards -1 > instead of toward 0. > > My first approach was to use fixed points, but then I hit issues where > some results also produced "wrong" numbers (according to the > reference), also in Pharo some ScaledDecimals compare as different > even when they're printed as the same (which is not correct, IMO). > > I just tested using everything as fractions and converting to float > (or ScaledDecimal) at the very last step and it produces the expected > result. I'll review and convert whatever is needed (including database > fields) to work with this. The good thing is that all the involved > numbers only have one decimal as much. > > Thanks! > > Esteban A. Maringolo > > On Tue, Jun 15, 2021 at 3:48 AM Steffen MÃ¤rcker <merkste(a)web.de> wrote: > > > > Have you considered using fixed-point arithmetic? For example: > > 7.1s2 roundTo: 0.1s2 > > > > The rule of thumb I stick to is to use FP only if I know the inaccuracies > > won't bite me. Funny enough, both 7.1 and 0.1 are already not accurately > > representable as floats. (And by coincidence, I prepared exam questions > > about floats for my students yesterday. ) > > > > Kind regards, > > Steffen > > > > > > Konrad Hinsen schrieb am Dienstag, 15. Juni 2021 07:02:30 (+02:00): > > > > > On 15/06/2021 01:03, Esteban Maringolo wrote: > > > > Sure, but what initiated this thread was a reference to roundTo: 0.1 > > > > which produced a "wrong" output. > > > > > > > > (9.1 + (-2.0)) roundTo: 0.1 "=> 7.1000000000000005" > > > > 7.1 roundTo: 0.1 "=> 7.1000000000000005" > > > > > > > > However, at this point I know that Pharo "does the right, raw, > thing" > > > > (at least compared to other mainstream languages), but it still > > > > produces a surprise effect. > > > > > > That's the "floating point surprise" that everyone has at some point, > no > > matter the language and runtime system. If that surprise is a problem for > > you, are you sure that floating-point arithmetic is what you really want? > > Maybe your needs are better served with integers and fractions. > > > > > > > > > Konrad. > > > > > > > > -- > > Gesendet mit Vivaldi Mail. Laden Sie Vivaldi kostenlos von vivaldi.com > > herunter. >

June 16, 2021

Re: Rounding in Floats

by Esteban Maringolo

On Wed, Jun 16, 2021 at 9:13 AM Konrad Hinsen <konrad.hinsen(a)fastmail.net> wrote: > > On 15/06/2021 16:05, Esteban Maringolo wrote: > > And in this particular case, it might cause issues, since the "full > > precision" (whatever that means) must be retained when using such a > > number to derive another one. > > To me, "full precision" means "no precision is ever lost in arithmetic > operations". If that's what you need, your choices are > > 1) Integers > > 2) Rational numbers (fractions) > Pharo has 1) and 2). Yeap, I'll switch to 2. What I'm not totally convinced of is whether to store numbers as integers (knowing beforehand the decimal precision, and converting it to fractions when read back) or if to store them as scaled decimals (which internally hold a fraction). Thanks!

June 16, 2021

Re: How to get dimensions (extent) of a SpPresenter

by Esteban Lorenzano

boo... format lost :P On Jun 16 2021, at 2:27 pm, Esteban Lorenzano <estebanlm(a)netc.eu> wrote: > > Hi, > Yes, it is there. > Thing is... since cairo does not informs correctly extent of surface in x11, what I did is to add an extra parameter to the drawing block, as you can see in the example : > > SpAthensPresenter>>#exampleResizing > | extent | > extent := 350@300. > self new > surfaceExtent: extent; > drawBlock: [ :aCanvas :boundingBox | | paint surface | > "Since sometimes a cairo surface does not brings the correct extent (in X11 or Windows, > for example), we use the bounding box of the component." > surface := aCanvas surface. > paint := surface > createLinearGradient: { > 0->Color red. > 1->Color green } > start: 0@0 > stop: boundingBox extent. > surface clear. > aCanvas setPaint: paint. > aCanvas drawShape: (0@0 extent: boundingBox extent) ]; > openWithSpec > > That was tested on Wayland and x11 and it was working properly :) > Esteban > > On Jun 16 2021, at 2:20 pm, kmo <voxkmp(a)gmail.com> wrote: > > Hi Esteban > > > > Do you know when the fix for the extent problem under Gtk will be in the > > image? I downloaded the latest Pharo 9 image a couple of days ago and, > > though the fix was in for the extent problem in Morphic, it still didn't > > work in Gtk. > > > > Thanks. > > Ken > > > > > > > > -- > > Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html > > >

June 16, 2021

Re: How to get dimensions (extent) of a SpPresenter

by Esteban Lorenzano

Hi, Yes, it is there. Thing is... since cairo does not informs correctly extent of surface in x11, what I did is to add an extra parameter to the drawing block, as you can see in the example : SpAthensPresenter>>#exampleResizing | extent | extent := 350@300. self new surfaceExtent: extent; drawBlock: [ :aCanvas :boundingBox | | paint surface | "Since sometimes a cairo surface does not brings the correct extent (in X11 or Windows, for example), we use the bounding box of the component." surface := aCanvas surface. paint := surface createLinearGradient: { 0->Color red. 1->Color green } start: 0@0 stop: boundingBox extent. surface clear. aCanvas setPaint: paint. aCanvas drawShape: (0@0 extent: boundingBox extent) ]; openWithSpec That was tested on Wayland and x11 and it was working properly :) Esteban On Jun 16 2021, at 2:20 pm, kmo <voxkmp(a)gmail.com> wrote: > Hi Esteban > > Do you know when the fix for the extent problem under Gtk will be in the > image? I downloaded the latest Pharo 9 image a couple of days ago and, > though the fix was in for the extent problem in Morphic, it still didn't > work in Gtk. > > Thanks. > Ken > > > > -- > Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html >

June 16, 2021

Re: How to get dimensions (extent) of a SpPresenter

by kmo

Hi Esteban Do you know when the fix for the extent problem under Gtk will be in the image? I downloaded the latest Pharo 9 image a couple of days ago and, though the fix was in for the extent problem in Morphic, it still didn't work in Gtk. Thanks. Ken -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

June 16, 2021