Squeak-dev July 1998

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by Alek 09 Jun '00

09 Jun '00

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Re: Re: Float bug toolkit: what the hash is this?
by Tim Olson 31 Aug '99

31 Aug '99

>>"[1]" (10 raisedToInteger: 600) = (10.0 raisedToInteger: 800) "alt-p" >>These are equal since both expressions end up answering a float with a >>special value indicating positive infinity. Positive infinities are always >>equal. > >Nonono.... (10 raisedToInteger: 600) is anInteger, while the other (if >finished correctly) is aFloat. Correct. The problem occurs when the #= message is sent to the LargePositiveInteger with the argument a Float (+Infinity). This causes the LargePositiveInteger to be adapted to a Float (resulting in +Infinity, as well). >If aFloat turns out to be infinite, an error >should be posted. This would have to be tested in the Float primitives in the VM whenever an overflow (or NaN, I suppose) is generated. However, I *think* (VM experts correct me, here) that all they can do is fail rather than returning a succesful value, so all of the Float code that invokes primitives would have to be rewritten to test and reflect this overflow/exception failure. The IEEE "default" operation is to silently return the default values (Inf or NaN), rather than generating an exception. What should the standard for Squeak be? -- tim

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Re: Sending WinSqueak Code: Dumb but Critical Question
by guzdial＠cc.gatech.edu 26 Aug '98

26 Aug '98

>You may try the attached CrLfFileStream which automatically detects the >actual line end convention of a file. To install it for permanent use >change FileStream class>>concreteStream to return CrLfFileStream rather >than StandardFileStream. > >Hope this helps, > Andreas Works great, Andreas! Thank you! My students are filing it in as a I type... Mark -------------------------- Mark Guzdial : Georgia Tech : College of Computing : Atlanta, GA 30332-0280 (404) 894-5618 : Fax (404) 894-0673 : guzdial(a)cc.gatech.edu http://www.cc.gatech.edu/gvu/people/Faculty/Mark.Guzdial.html

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Porting troubles
by Georg Gollmann 26 Aug '98

26 Aug '98

As a learning experience I have tried porting Squeak to Linux/m68k (Debian 2.0beta). While the make process ran without a problem (thanks Ian!) I quickly faced a segmentation fault when running Squeak (in the incrementalGC when the lowSpaceWatcher is installed, to be precise). Inspecting the variables I found following: (gdb) print memory $22 = (unsigned char *) 0xc0151008 "À\026\030I\r\"" (gdb) print endOfMemory $11 = -1068549284 As I read it the memory has been malloced high up and all those ints that represent addresses have become negative, breaking the pointer arithmetic. So...shouldn´t all variables that hold addresses (OOPs) be declared as unsigned instead of int (or am I barking up the wrong tree) ? Georg ---- Dipl.Ing. Georg Gollmann TU-Wien, EDV-Zentrum phon:(+43-1) 58801 - 5848 fax: (+43-1) 587 42 11 mail:gollmann@edvz.tuwien.ac.at http://macos.tuwien.ac.at/Gollmann.html

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Performance hit
by Bob Arning 30 Jul '98

30 Jul '98

In doing some testing that involved Processes waiting on timers, I was puzzled by poor performance. Digging deeper I finally narrowed it down to this example: PWatch class>>runTests3: runTests3: howMany | block alone done notAlone | alone _ notAlone _ 0. block _ [ Time millisecondsToRun: [100 timesRepeat: [howMany factorial]] ]. 3 timesRepeat: [alone _ alone + block value]. done _ false. [(Delay forSeconds: 30) wait. done _ true] forkAt: 6. 3 timesRepeat: [notAlone _ notAlone + block value]. [done] whileFalse. Transcript show: howMany asString, ' alone = ',(alone // 3) asString, ' notAlone = ',(notAlone // 3) asString; cr. Then, when I evaluate: 5 to: 30 by: 5 do: [ :howMany | PWatch runTests3: howMany] I get: 5 alone = 3 notAlone = 3 10 alone = 4 notAlone = 5 15 alone = 54 notAlone = 292 20 alone = 161 notAlone = 967 25 alone = 248 notAlone = 1661 30 alone = 379 notAlone = 2635 When we go from 10 factorial to 15 factorial (when the result crosses from SmallInteger to LargeInteger), performance drops by a factor of 5 or 6 *IF* another process is waiting on a timer to expire. Looking at the interpreter source, after every primitive dispatch, there is if (successFlag && ((nextWakeupTick != 0) && (((ioMSecs()) & 536870911) >= nextWakeupTick))) { interruptCheckCounter = 1000; checkForInterrupts(); } There are comments (in the Mac version, anyway) as to there being two routines available for getting a millisecond clock value and that the more expensive is used for greater accuracy. Perhaps this might be a spot to use the cheaper variety with a suitable allowance for accuracy. Any thoughts? Cheers, Bob

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cooperative / preemptive scheduling
by Tim Olson 30 Jul '98

30 Jul '98

Posted to thread in comp.lang.smalltalk: [the thread is discussing the Smalltalk scheduling model, where processes of the same priority are scheduled cooperatively, while higher-priority processes preempt lower-priority processes. Eliot points out that if a higher-priority preemption caused the preempted process to be added to the back of its priority queue instead of the front, then this is an implicit yield which can break the cooperative scheduling model] In article <35C00BEA.7BA02C3D(a)best.com>, Pete Cockerell <petec(a)best.com> wrote: | Eliot & Linda wrote: | >[Blue book/VSE task switching bug] | | Still, at least ST has a standard process model, arf arf... | | > I don't know what happens in VisualAge, Dolphin, Smalltalk MT, et al. | > Can anyone say what happens? Squeak, not surprisingly, follows the Blue Book and causes an implicit yield. | > Any other implementors agree/disagree that | > the blue book spec's implicit yield on preemption is a bug? | | Not speaking as an implementor, I would say it strikes me as anomolous, to | say the least. It breaks the model of equal-priority processes not being | pre-empted by their 'siblings', albeit indirectly. I tend to agree with Eliot. The benefit of the cooperative model is that one can know and control exactly at what points yields to same-priority processes occur, so explicit exclusion code can be avoided in many cases. With higher-priority processes causing an implicit yield, this breaks. Also, if an implicit yield is desired, it could be coded in the higher-priority process by explicitly manipulating the process queues. The converse isn't true; the higher-priority process has no knowledge of which lower-priority process was preempted, so it doesn't know which priority queue to manipulate. I don't know, however, what might break if Squeak were to put preempted processes at the front of their queue instead of the back. Any Squeak VM hackers want to try this? -- tim

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Re: Bug tracking
by jim benson 30 Jul '98

30 Jul '98

Tim Rowledge wrote: > Try a swiki. Provides access for users to point out bugs, see what (if > > anything ) you have been able to do about it, a place for the fix-code > and > so on. I like this idea. > Works for me (well it would, but I never put bugs in my code :-P ) > You do not know how much that hurt :) Not only that, but I had to admit in public my failings. jim

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Re: Bug tracking
by jim benson 30 Jul '98

30 Jul '98

Eliot & Linda wrote: > One thing I';ve seen people do at ParcPlace is to use the system. > e.g. > > !Object methodsFor: 'error handling'! > commentOnly > ^self error: 'method for comment only' > > bug: aMessage > "Change to true if you want bugs to halt execution" > false ifTrue: > ["Change to Transcript show: ... if you want a record" > > ^self error: 'method contains bug: ', aMessage]! ! > [snip] This works when you know which method contains the bug. Unfortunately, my bugs tend to be more systemic. E.g. the cursor is not the correct shape when it interacts with such and such an item on the screen. Typically, an end user describes the result of the bug and rather rudely omits which method is causing the error, and expects me to find the bug and fix it ! Because I am making system level changes, I usually end up going on bug hunts which generally are one hour trips deep into the inner workings of Squeak. I rarely get to address the bug when it is first presented, thus the bug report. I am interested though in how this solution scales when several people are working on the system at once, and how you divvy up bug fixes among a group when using this tracking method. Thanks for the idea, jim benson

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Bug tracking
by jim benson 29 Jul '98

29 Jul '98

Well, Okay, so my little native window project has gotten a little bit bigger than I thought it would and ... Straight out -- it has bugs, and unfortunately more than I can keep track of in my head. How do I track those bad boys and mark their extermination ? My current clever solution is to write them down in a text file, one section marked "bugs" another section marked "enhancements" and write down when the bug was exterminated, along with the time and date, and a short description of the fix. BTW, this is even more clever than my previous method. My previous method was to write the bug down on a scrap piece of paper, ( with an illuminating drawing if possible). I would collect the papers in a bug pile. Invariably, I would need to clean my desk off, and sort thru the bug pile. Since I could rarely make heads or tails out of what I had written previously ( lucid insights into the inner workings of the system in the middle of the night somehow do not seem quite as brilliant in the light of day a couple of weeks later ), I usually end up just throwing away most of the older bug reports. Instinctively, I know that if a bug is bad enough, it will show up later. This has the added bonus of limiting the number of bugs I need to fix to the bugs that I can explain coherently on a piece of paper. This helps sharpen both my writing, drawing and programming skills all at once! Realizing that other people may have this problem, I write to you hoping that a Squeak based solution exists. This probably involves something of a task list/ priority type of system. Help jim benson

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Ian Piumarta Squeak Presentation at Esug'98
by ducasse＠iam.unibe.ch 29 Jul '98

29 Jul '98

Check the program. Call for participation ESUG Smalltalk Summer School for experienced Smalltalkers Brescia, Italy August 31st to September 4th 1998 http://www.esug.org/ ESUG (European Smalltalk Users' Group) will hold its sixth Smalltalk Summer School in Brescia, Italy, from August 31st to September 4th 1998. This will be a unique opportunity for attendees to meet well-known european Smalltalkers from both the academic and industrial fields, and to gain hands-on experience of Smalltalk's most advanced techniques. Non-european Smalltalkers are of course welcome. The summer school is a non-profit event organized by ESUG. This year it will be supported by the Catholic University of Brescia, in the north of Italy, and sponsor by Gemstone. Organizing Committee: ---------------- Lorenzo SCHIAVINA, Gruppo EDOR, Italy Darin MCLEAN, Gruppo EDOR, Italy Isabelle BORNE, cole des Mines de Nantes, France Annick FRON, AFC Europe, France David GRIETENS , HIGHQ BVBA, Belgium Philippe KRIEF, OTI, France Ernest MICKLEI, ELC Object Technology, The Netherlands Rob VENS, Sepher Software, The Netherlands Speakers: -------- Jay Almarode, Gemstone, USA Jason Ayers, ObjectShare, UK David Grietens, HIGHQ BVBA, Belgium Don Roberts, University of Illinois, USA John Brant, University of Illinois, USA Anna Ottobelli, IBM, italy Ian Piumarta, INRIA, France Lorenzo Schiavina, Gruppo EDOR, Italy Joachim Geidel, Daedalos, Germany Andy Berry, The Object Factory, UK Peter Werner, Deutsche Telekom, Germany Markus Arikan, Germany Kirk Blackburn, BDM International, USA Mireille Fornarino, ESSI, France Anne-marie Pinna, ESSI, France Stephane Ducasse, University of Bern, Switzerland Roel Wuyts, Vrije Universiteit Brussel, Belgium About the speakers ----------------- All speakers are well-known Smalltalk specialists with either academic or industrial background. All tutorials will be supported by exercises on machines and extensive notes. Potential attendees ------------------- Both intermediate and advanced-level Smalltalk programmers experienced in any Smalltalk systems. Summer school program and general information --------------------------------------------- the detailed program and all information concerning the summer school can be found on the ESUG web page : http://www.esug.org/ __________________________________________________________________________ REGISTRATION REGISTRATION FEES ----------------- Registration fees include the proceedings, lunches and coffee breaks. Students and education 1500 FF Industrial companies 3500 FF Esug members will get a 300 FF discount. Special fees can be negotiated if you plan to come one or two days only. Contact the ESUG board at : info(a)esug.org A special dinner (extra costs) will be organized. ___________________________________________________________________________ ESUG 98 Summer School Brescia (Italy)August 31th September 4th 1998 Registration form First Name ............................................ Last Name ............................................. Organization .......................................... ........................................................ Position .............................................. Address ............................................... ........................................................ Postal Code .............. City ..................... Country ........................... Telephone ......................... Fax ............................... E-mail ............................ Smalltalk Systems used: ....................... ---------------------- Status: Education Industry ------ Esug membership: --------------- Yes No Total Payment (in FF): Methods of Payment ------------------ [] CHECK to "ESUG" [] TRANSFER to "European Smalltalk Users' Group" (in French Francs) Bank code: 30004 Counter code: 00886 Account number: 00004536316 RIB key: 11 Bank name: BNP Paris Dupleix Bank address: Banque Nationale de Paris Agence Dupleix 26 boulevard de Grenelle 75015 PARIS FRANCE Conference dinner (extra cost) ----------------- number of persons: dietary requirements(vegetarians or not): Special wishes -------------- - Do you wish to organize a session outside of the program (demonstration, ...)? - Any suggestion ? Date: .......................... Signature _____________________________________________________________________________ Return this form - electronically to: info(a)esug.org - by ordinary mail (your payment) UNTIL AUGUST 5th to: ESUG c/o Isabelle BORNE 20 avenue Jacques Tati 44300 NANTES FRANCE AFTER AUGUST 5th to: Annick Fron AFC Europe 48, avenue du Docteur Lefebvre B.P. 111 F-06271 Villeneuve-Loubet Cedex FRANCE

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