September 2011 - Pharo-dev - lists.pharo.org

Re: [Pharo-project] Two objects with same hash

by Mariano Martinez Peck

On Fri, Sep 23, 2011 at 3:02 PM, Denis Kudriashov <dionisiydk(a)gmail.com>wrote: > Thank you for all your responses. I will use UUID. > > Another assumption: > I know there is a trick to get object memory address. > which one? > Can it be used for object identity? (inside memory of objects) > > > > * > * > 2011/9/23 Marcus Denker <marcus.denker(a)inria.fr> > >> >> On Sep 23, 2011, at 1:08 PM, Denis Kudriashov wrote: >> >> > Hello, >> > >> > I use hash message to generate unique object id. (unique between current >> memory objects). >> > And I catch situation when two objects has same hash value. Objects has >> been created in loop almost at same time. >> > >> > So my question - is it really possible? >> >> Yes, easily, as there are only 12 bits for the hash, there are only 4096 >> different hash values. >> >> This means that a hash is *not* at all a UUID, and all hashing data >> structures need to be optimized >> for the case of hash collision, as it will happen a lot. >> >> Marcus >> >> >> -- >> Marcus Denker -- http://marcusdenker.de >> >> >> > -- Mariano http://marianopeck.wordpress.com

Sept. 23, 2011

Re: [Pharo-project] Two objects with same hash

by Denis Kudriashov

Thank you for all your responses. I will use UUID. Another assumption: I know there is a trick to get object memory address. Can it be used for object identity? (inside memory of objects) * * 2011/9/23 Marcus Denker <marcus.denker(a)inria.fr> > > On Sep 23, 2011, at 1:08 PM, Denis Kudriashov wrote: > > > Hello, > > > > I use hash message to generate unique object id. (unique between current > memory objects). > > And I catch situation when two objects has same hash value. Objects has > been created in loop almost at same time. > > > > So my question - is it really possible? > > Yes, easily, as there are only 12 bits for the hash, there are only 4096 > different hash values. > > This means that a hash is *not* at all a UUID, and all hashing data > structures need to be optimized > for the case of hash collision, as it will happen a lot. > > Marcus > > > -- > Marcus Denker -- http://marcusdenker.de > > >

Sept. 23, 2011

Re: [Pharo-project] looking for boring morphs

by StÃ©phane Ducasse

Indeed having components would be good. I remember one morph maskedTextMorph we integrated but removed. Stef On Sep 23, 2011, at 2:47 PM, Esteban Lorenzano wrote: > Hi, > I have a customer who are asking me for a very small app... but a desktop app, not the usual web app I'm more used to do... > and of course, I'm doing it with pharo! > So far... this is working really well... much easier as I supposed it would be :) > I'm using glamour, magritte, keybindings, hpdf, mongodb... and small tweaks by my self to make it work as expected, but not so much. > > (btw... I want to say that a couple of years ago, this wont be an option at all... this is due to the great effort the pharo community is doing, and I'm really proud of it. Thank you guys!) > > well... now... I need some morphs a regular management application usually needs: > > 1) NumberInputFieldMorph (A child of TextMorph or PluggableTextMorph who allows different kind of numbers -> this is easy to do, but better if it is already somewhere) > 2) DateInputFieldMorph (a morph with a "date picker" -> this is harder, because I have very limited knowledge about morphic) > 3) I'm sure there are others I didn't needed yet, but there are needed in this kind of applications > > so... does someone has this kind of morphs somewhere? I would really appreciate it, because you know... it is doable, but time is tyrant and better if I can reuse someones work ;) > > cheers, > Esteban

Sept. 23, 2011

Re: [Pharo-project] Two objects with same hash

by Levente Uzonyi

On Fri, 23 Sep 2011, Marcus Denker wrote: > > On Sep 23, 2011, at 1:08 PM, Denis Kudriashov wrote: > >> Hello, >> >> I use hash message to generate unique object id. (unique between current memory objects). >> And I catch situation when two objects has same hash value. Objects has been created in loop almost at same time. >> >> So my question - is it really possible? > > Yes, easily, as there are only 12 bits for the hash, there are only 4096 different hash values. > > This means that a hash is *not* at all a UUID, and all hashing data structures need to be optimized > for the case of hash collision, as it will happen a lot. Not all hashed collections, just those which rely on identityHash. Also, they are not fully optimized. Significant improvements can be done with a new primitive. Levente > > Marcus > > > -- > Marcus Denker -- http://marcusdenker.de > > >

Sept. 23, 2011

[Pharo-project] looking for boring morphs

by Esteban Lorenzano

Hi, I have a customer who are asking me for a very small app... but a desktop app, not the usual web app I'm more used to do... and of course, I'm doing it with pharo! So far... this is working really well... much easier as I supposed it would be :) I'm using glamour, magritte, keybindings, hpdf, mongodb... and small tweaks by my self to make it work as expected, but not so much. (btw... I want to say that a couple of years ago, this wont be an option at all... this is due to the great effort the pharo community is doing, and I'm really proud of it. Thank you guys!) well... now... I need some morphs a regular management application usually needs: 1) NumberInputFieldMorph (A child of TextMorph or PluggableTextMorph who allows different kind of numbers -> this is easy to do, but better if it is already somewhere) 2) DateInputFieldMorph (a morph with a "date picker" -> this is harder, because I have very limited knowledge about morphic) 3) I'm sure there are others I didn't needed yet, but there are needed in this kind of applications so... does someone has this kind of morphs somewhere? I would really appreciate it, because you know... it is doable, but time is tyrant and better if I can reuse someones work ;) cheers, Esteban

Sept. 23, 2011

Re: [Pharo-project] Two objects with same hash

by Henrik Sperre Johansen

On 23.09.2011 13:08, Denis Kudriashov wrote: > Hello, > > I use hash message to generate unique object id. (unique between > current memory objects). > And I catch situation when two objects has same hash value. Objects > has been created in loop almost at same time. > > So my question - is it really possible? > Can it be bug in my current VM which I used? (it is cog but very old) Old Cog vm's gave objects sequential and (in some cases identical) hash values. IIRC, current ones no longer give identical. However, there are only 4096 unique identity hashes, so you need another solution. > > What you can recomment me for unique object id? > > Best regards, > Denis Either a unique sequence, or UUID as Mariano suggests (sequence is probably faster). Some care is required if you need it to be thread-safe though. For an approach to avoid (and some more discussion of the same problem), you can read http://forum.world.st/DateAndTime-and-TimeStamp-precision-td1486046.html#a1… Cheers, Henry

Sept. 23, 2011

Re: [Pharo-project] "Missing Pharo feature: undo close workspace. #Smalltalk"

by Clara Allende

Yay! Awesome :D On 23 September 2011 09:20, Sven Van Caekenberghe <sven(a)beta9.be> wrote: > > On 23 Sep 2011, at 14:13, Mariano Martinez Peck wrote: > > > Since I don't have twitter, I answe here. > > The feature is already there. If you have closed the workspace, then open > a new one, press in the small arrow in the top corner, select "previous > contents" and it should be there... > > > > cheers > > Very nice, never knew about thatâ¦ > > Sven > -- "*Most good programmers do programming not because they expect to get paid or get adulation by the public, but because it is fun to program.*" Linus Torvalds

Sept. 23, 2011

Re: [Pharo-project] "Missing Pharo feature: undo close workspace. #Smalltalk"

by Sven Van Caekenberghe

On 23 Sep 2011, at 14:13, Mariano Martinez Peck wrote: > Since I don't have twitter, I answe here. > The feature is already there. If you have closed the workspace, then open a new one, press in the small arrow in the top corner, select "previous contents" and it should be there... > > cheers Very nice, never knew about thatâ¦ Sven

Sept. 23, 2011

[Pharo-project] "Missing Pharo feature: undo close workspace. #Smalltalk"

by Mariano Martinez Peck

Since I don't have twitter, I answe here. The feature is already there. If you have closed the workspace, then open a new one, press in the small arrow in the top corner, select "previous contents" and it should be there... cheers -- Mariano http://marianopeck.wordpress.com

Sept. 23, 2011

Re: [Pharo-project] Two objects with same hash

by Mariano Martinez Peck

On Fri, Sep 23, 2011 at 1:08 PM, Denis Kudriashov <dionisiydk(a)gmail.com>wrote: > Hello, > > I use hash message to generate unique object id. (unique between current > memory objects). > And I catch situation when two objects has same hash value. Objects has > been created in loop almost at same time. > > So my question - is it really possible? > Can it be bug in my current VM which I used? (it is cog but very old) > > What you can recomment me for unique object id? > What marcus said is correct. THe only easy way is to have an instVar in your objects. You can put instances of UUID. UUID new -> 545bd8d5-18d5-41c0-b11a-63d82dcef783 Otherwise, if you are lucky and you have domain objects (like Person >> id) that can use they own implementation of #hash, do it !! > Best regards, > Denis > -- Mariano http://marianopeck.wordpress.com

Sept. 23, 2011