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

Re: [Pharo-project] [Vm-dev] Re: About ~= and ~~

by Mariano Martinez Peck

On Wed, Oct 12, 2011 at 7:29 PM, Eliot Miranda <eliot.miranda(a)gmail.com>wrote: > > > > On Wed, Oct 12, 2011 at 10:26 AM, Mariano Martinez Peck < > marianopeck(a)gmail.com> wrote: > >> >> >> >> On Wed, Oct 12, 2011 at 6:44 PM, Eliot Miranda <eliot.miranda(a)gmail.com>wrote: >> >>> >>> >>> >>> On Wed, Oct 12, 2011 at 8:38 AM, Levente Uzonyi <leves(a)elte.hu> wrote: >>> >>>> On Wed, 12 Oct 2011, Clara Allende wrote: >>>> >>>> Hi guys, >>>>> >>>>> I'm wondering, why? >>>>> >>>>> ProtoObject>> ~~ anObject >>>>> "Answer whether the receiver and the argument are not the same object >>>>> (do not have the same object pointer)." >>>>> >>>>> self == anObject >>>>> ifTrue: [^ false] >>>>> ifFalse: [^ true] >>>>> >>>>> Instead of: >>>>> ProtoObject>> ~~ anObject >>>>> "Answer whether the receiver and the argument are not the same object >>>>> (do not have the same object pointer)." >>>>> >>>>> ^(self == anObject) not >>>>> >>>>> And why? >>>>> Object >> ~= anObject >>>>> "Answer whether the receiver and the argument do not represent the >>>>> same object." >>>>> >>>>> ^self = anObject == false >>>>> >>>>> Instead of >>>>> Object>> ~= anObject >>>>> "Answer whether the receiver and the argument do not represent the >>>>> same object." >>>>> >>>>> ^(self = anObject) not. >>>>> >>>>> Is there any particular reason for this that I'm missing? >>>>> >>>> >>>> Performance. >>>> >>> >>> But better still is to add a ~~ primitive. I did this for VisualWorks. >>> e.g. primitive 150 is free. why don't we use that for 1.4/4.3? >>> >>> >> >> with or without special bytecode associated? >> > > Initially without. > +1 > Dynamic frequency is low, and primitive adds significant performance over > the non-primitive version. One could use the blockCopy: special bytecode > but I'd wait until doing a complete bytecode set redesign. > > >> >> >> >>> >>>> >>>> Levente >>>> >>>> Thanks in advance! >>>>> -- >>>>> >>>>> "*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 >>>>> >>>>> >>>> >>> >>> >>> -- >>> best, >>> Eliot >>> >>> >>> >> >> >> -- >> Mariano >> http://marianopeck.wordpress.com >> >> >> > > > -- > best, > Eliot > > > -- Mariano http://marianopeck.wordpress.com

Oct. 12, 2011

Re: [Pharo-project] [Vm-dev] Re: About ~= and ~~

by Eliot Miranda

On Wed, Oct 12, 2011 at 10:26 AM, Mariano Martinez Peck < marianopeck(a)gmail.com> wrote: > > > > On Wed, Oct 12, 2011 at 6:44 PM, Eliot Miranda <eliot.miranda(a)gmail.com>wrote: > >> >> >> >> On Wed, Oct 12, 2011 at 8:38 AM, Levente Uzonyi <leves(a)elte.hu> wrote: >> >>> On Wed, 12 Oct 2011, Clara Allende wrote: >>> >>> Hi guys, >>>> >>>> I'm wondering, why? >>>> >>>> ProtoObject>> ~~ anObject >>>> "Answer whether the receiver and the argument are not the same object >>>> (do not have the same object pointer)." >>>> >>>> self == anObject >>>> ifTrue: [^ false] >>>> ifFalse: [^ true] >>>> >>>> Instead of: >>>> ProtoObject>> ~~ anObject >>>> "Answer whether the receiver and the argument are not the same object >>>> (do not have the same object pointer)." >>>> >>>> ^(self == anObject) not >>>> >>>> And why? >>>> Object >> ~= anObject >>>> "Answer whether the receiver and the argument do not represent the >>>> same object." >>>> >>>> ^self = anObject == false >>>> >>>> Instead of >>>> Object>> ~= anObject >>>> "Answer whether the receiver and the argument do not represent the >>>> same object." >>>> >>>> ^(self = anObject) not. >>>> >>>> Is there any particular reason for this that I'm missing? >>>> >>> >>> Performance. >>> >> >> But better still is to add a ~~ primitive. I did this for VisualWorks. >> e.g. primitive 150 is free. why don't we use that for 1.4/4.3? >> >> > > with or without special bytecode associated? > Initially without. Dynamic frequency is low, and primitive adds significant performance over the non-primitive version. One could use the blockCopy: special bytecode but I'd wait until doing a complete bytecode set redesign. > > > >> >>> >>> Levente >>> >>> Thanks in advance! >>>> -- >>>> >>>> "*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 >>>> >>>> >>> >> >> >> -- >> best, >> Eliot >> >> >> > > > -- > Mariano > http://marianopeck.wordpress.com > > > -- best, Eliot

Oct. 12, 2011

Re: [Pharo-project] [Vm-dev] Re: About ~= and ~~

by Mariano Martinez Peck

On Wed, Oct 12, 2011 at 6:44 PM, Eliot Miranda <eliot.miranda(a)gmail.com>wrote: > > > > On Wed, Oct 12, 2011 at 8:38 AM, Levente Uzonyi <leves(a)elte.hu> wrote: > >> On Wed, 12 Oct 2011, Clara Allende wrote: >> >> Hi guys, >>> >>> I'm wondering, why? >>> >>> ProtoObject>> ~~ anObject >>> "Answer whether the receiver and the argument are not the same object >>> (do not have the same object pointer)." >>> >>> self == anObject >>> ifTrue: [^ false] >>> ifFalse: [^ true] >>> >>> Instead of: >>> ProtoObject>> ~~ anObject >>> "Answer whether the receiver and the argument are not the same object >>> (do not have the same object pointer)." >>> >>> ^(self == anObject) not >>> >>> And why? >>> Object >> ~= anObject >>> "Answer whether the receiver and the argument do not represent the >>> same object." >>> >>> ^self = anObject == false >>> >>> Instead of >>> Object>> ~= anObject >>> "Answer whether the receiver and the argument do not represent the >>> same object." >>> >>> ^(self = anObject) not. >>> >>> Is there any particular reason for this that I'm missing? >>> >> >> Performance. >> > > But better still is to add a ~~ primitive. I did this for VisualWorks. > e.g. primitive 150 is free. why don't we use that for 1.4/4.3? > > with or without special bytecode associated? > >> >> Levente >> >> Thanks in advance! >>> -- >>> >>> "*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 >>> >>> >> > > > -- > best, > Eliot > > > -- Mariano http://marianopeck.wordpress.com

Oct. 12, 2011

Re: [Pharo-project] About ~= and ~~

by Alexandre Bergel

Ok, scheduling in Pharo may happen when sending a message. Thanks for the clarification. Cheers, Alexandre On 12 Oct 2011, at 13:40, StÃ©phane Ducasse wrote: > Alex > > the vm should check condition from time to time and the place where it can check is at every message send. > Since == is not a message send, when you write code with == or not even if it is semantically equivalent > its execution may be different (it looks hackish). > > Stef > > On Oct 12, 2011, at 6:29 PM, Alexandre Bergel wrote: > >> Excellent description. >> Just wondering: when the scheduling really happens? I thought that it is when you do a #yield or wait explicitely since scheduling is not preemptive. >> >> Cheers, >> Alexandre >> >> >> On 12 Oct 2011, at 12:49, Mariano Martinez Peck wrote: >> >>> >>> >>> On Wed, Oct 12, 2011 at 5:38 PM, Levente Uzonyi <leves(a)elte.hu> wrote: >>> On Wed, 12 Oct 2011, Clara Allende wrote: >>> >>> Hi guys, >>> >>> I'm wondering, why? >>> >>> ProtoObject>> ~~ anObject >>> "Answer whether the receiver and the argument are not the same object >>> (do not have the same object pointer)." >>> >>> self == anObject >>> ifTrue: [^ false] >>> ifFalse: [^ true] >>> >>> >>> Hi Carla. I can think about two things. The first one, is the one Levente said, performance. >>> If you analyze the bycode of this method, you will see that it is extremely fast because: >>> >>> 1) #== has an special associated bytecode, that is, them VM maps such bytecode to an specific primitive and it is directly executed. It means that the method #== is really never sent. >>> 2) ifTrue:ifFalse: is also optimized (inlined) by the compiler. Again, it method is never executed and instead the compiler replace a message send bytecode with jump ones. >>> >>> Another possible reason (it may not be the case, but in another places it is), is to prevent VM interruption for check other processes. In summary, the VM checks whether it should execute another process of the queue after a method execution. As you know, some parts of the scheduling process is done at the image side. And from there we lack a way to say to the VM, "please execute this method without checking others processes". Hence, in a few yet very specific places of PRocess, Scheduler, Semaphore, etc, #== is used as a mean of executing something WITHOUT being interrupted. I can imagine that it may happen the same with #~~. So if you implement such method with a #not, you will indeed send a message, proving a possibilty to be interrupted. >>> >>> Another reasons, similar to the previous one, is that sometimes #== is also used as a way to avoid executing method. So..there are some methods (I don't remember if #allInstancesDo: or #allObjectsDo:) will loop forever because the loop condition would be creating objects (remember that method execution creates objects such as MethodContext). >>> So...again, I think it may happen the same with #~~. >>> >>> That being said, I agree that the method deserve a GOOD comment explaining the reasons of such optimization. >>> >>> Cheers >>> >>> >>> Instead of: >>> ProtoObject>> ~~ anObject >>> "Answer whether the receiver and the argument are not the same object >>> (do not have the same object pointer)." >>> >>> ^(self == anObject) not >>> >>> And why? >>> Object >> ~= anObject >>> "Answer whether the receiver and the argument do not represent the >>> same object." >>> >>> ^self = anObject == false >>> >>> Instead of >>> Object>> ~= anObject >>> "Answer whether the receiver and the argument do not represent the >>> same object." >>> >>> ^(self = anObject) not. >>> >>> Is there any particular reason for this that I'm missing? >>> >>> Performance. >>> >>> >>> Levente >>> >>> Thanks in advance! >>> -- >>> >>> "*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 >>> >>> >>> >>> >>> >>> -- >>> Mariano >>> http://marianopeck.wordpress.com >>> >> >> -- >> _,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;: >> Alexandre Bergel http://www.bergel.eu >> ^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;. >> >> >> >> >> >> > > -- _,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;: Alexandre Bergel http://www.bergel.eu ^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;.

Oct. 12, 2011

Re: [Pharo-project] About ~= and ~~

by Eliot Miranda

On Wed, Oct 12, 2011 at 8:38 AM, Levente Uzonyi <leves(a)elte.hu> wrote: > On Wed, 12 Oct 2011, Clara Allende wrote: > > Hi guys, >> >> I'm wondering, why? >> >> ProtoObject>> ~~ anObject >> "Answer whether the receiver and the argument are not the same object >> (do not have the same object pointer)." >> >> self == anObject >> ifTrue: [^ false] >> ifFalse: [^ true] >> >> Instead of: >> ProtoObject>> ~~ anObject >> "Answer whether the receiver and the argument are not the same object >> (do not have the same object pointer)." >> >> ^(self == anObject) not >> >> And why? >> Object >> ~= anObject >> "Answer whether the receiver and the argument do not represent the >> same object." >> >> ^self = anObject == false >> >> Instead of >> Object>> ~= anObject >> "Answer whether the receiver and the argument do not represent the >> same object." >> >> ^(self = anObject) not. >> >> Is there any particular reason for this that I'm missing? >> > > Performance. > But better still is to add a ~~ primitive. I did this for VisualWorks. e.g. primitive 150 is free. why don't we use that for 1.4/4.3? > > > Levente > > Thanks in advance! >> -- >> >> "*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 >> >> > -- best, Eliot

Oct. 12, 2011

Re: [Pharo-project] About ~= and ~~

by StÃ©phane Ducasse

Alex the vm should check condition from time to time and the place where it can check is at every message send. Since == is not a message send, when you write code with == or not even if it is semantically equivalent its execution may be different (it looks hackish). Stef On Oct 12, 2011, at 6:29 PM, Alexandre Bergel wrote: > Excellent description. > Just wondering: when the scheduling really happens? I thought that it is when you do a #yield or wait explicitely since scheduling is not preemptive. > > Cheers, > Alexandre > > > On 12 Oct 2011, at 12:49, Mariano Martinez Peck wrote: > >> >> >> On Wed, Oct 12, 2011 at 5:38 PM, Levente Uzonyi <leves(a)elte.hu> wrote: >> On Wed, 12 Oct 2011, Clara Allende wrote: >> >> Hi guys, >> >> I'm wondering, why? >> >> ProtoObject>> ~~ anObject >> "Answer whether the receiver and the argument are not the same object >> (do not have the same object pointer)." >> >> self == anObject >> ifTrue: [^ false] >> ifFalse: [^ true] >> >> >> Hi Carla. I can think about two things. The first one, is the one Levente said, performance. >> If you analyze the bycode of this method, you will see that it is extremely fast because: >> >> 1) #== has an special associated bytecode, that is, them VM maps such bytecode to an specific primitive and it is directly executed. It means that the method #== is really never sent. >> 2) ifTrue:ifFalse: is also optimized (inlined) by the compiler. Again, it method is never executed and instead the compiler replace a message send bytecode with jump ones. >> >> Another possible reason (it may not be the case, but in another places it is), is to prevent VM interruption for check other processes. In summary, the VM checks whether it should execute another process of the queue after a method execution. As you know, some parts of the scheduling process is done at the image side. And from there we lack a way to say to the VM, "please execute this method without checking others processes". Hence, in a few yet very specific places of PRocess, Scheduler, Semaphore, etc, #== is used as a mean of executing something WITHOUT being interrupted. I can imagine that it may happen the same with #~~. So if you implement such method with a #not, you will indeed send a message, proving a possibilty to be interrupted. >> >> Another reasons, similar to the previous one, is that sometimes #== is also used as a way to avoid executing method. So..there are some methods (I don't remember if #allInstancesDo: or #allObjectsDo:) will loop forever because the loop condition would be creating objects (remember that method execution creates objects such as MethodContext). >> So...again, I think it may happen the same with #~~. >> >> That being said, I agree that the method deserve a GOOD comment explaining the reasons of such optimization. >> >> Cheers >> >> >> Instead of: >> ProtoObject>> ~~ anObject >> "Answer whether the receiver and the argument are not the same object >> (do not have the same object pointer)." >> >> ^(self == anObject) not >> >> And why? >> Object >> ~= anObject >> "Answer whether the receiver and the argument do not represent the >> same object." >> >> ^self = anObject == false >> >> Instead of >> Object>> ~= anObject >> "Answer whether the receiver and the argument do not represent the >> same object." >> >> ^(self = anObject) not. >> >> Is there any particular reason for this that I'm missing? >> >> Performance. >> >> >> Levente >> >> Thanks in advance! >> -- >> >> "*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 >> >> >> >> >> >> -- >> Mariano >> http://marianopeck.wordpress.com >> > > -- > _,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;: > Alexandre Bergel http://www.bergel.eu > ^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;. > > > > > >

Oct. 12, 2011

Re: [Pharo-project] About ~= and ~~

by Alexandre Bergel

Excellent description. Just wondering: when the scheduling really happens? I thought that it is when you do a #yield or wait explicitely since scheduling is not preemptive. Cheers, Alexandre On 12 Oct 2011, at 12:49, Mariano Martinez Peck wrote: > > > On Wed, Oct 12, 2011 at 5:38 PM, Levente Uzonyi <leves(a)elte.hu> wrote: > On Wed, 12 Oct 2011, Clara Allende wrote: > > Hi guys, > > I'm wondering, why? > > ProtoObject>> ~~ anObject > "Answer whether the receiver and the argument are not the same object > (do not have the same object pointer)." > > self == anObject > ifTrue: [^ false] > ifFalse: [^ true] > > > Hi Carla. I can think about two things. The first one, is the one Levente said, performance. > If you analyze the bycode of this method, you will see that it is extremely fast because: > > 1) #== has an special associated bytecode, that is, them VM maps such bytecode to an specific primitive and it is directly executed. It means that the method #== is really never sent. > 2) ifTrue:ifFalse: is also optimized (inlined) by the compiler. Again, it method is never executed and instead the compiler replace a message send bytecode with jump ones. > > Another possible reason (it may not be the case, but in another places it is), is to prevent VM interruption for check other processes. In summary, the VM checks whether it should execute another process of the queue after a method execution. As you know, some parts of the scheduling process is done at the image side. And from there we lack a way to say to the VM, "please execute this method without checking others processes". Hence, in a few yet very specific places of PRocess, Scheduler, Semaphore, etc, #== is used as a mean of executing something WITHOUT being interrupted. I can imagine that it may happen the same with #~~. So if you implement such method with a #not, you will indeed send a message, proving a possibilty to be interrupted. > > Another reasons, similar to the previous one, is that sometimes #== is also used as a way to avoid executing method. So..there are some methods (I don't remember if #allInstancesDo: or #allObjectsDo:) will loop forever because the loop condition would be creating objects (remember that method execution creates objects such as MethodContext). > So...again, I think it may happen the same with #~~. > > That being said, I agree that the method deserve a GOOD comment explaining the reasons of such optimization. > > Cheers > > > Instead of: > ProtoObject>> ~~ anObject > "Answer whether the receiver and the argument are not the same object > (do not have the same object pointer)." > > ^(self == anObject) not > > And why? > Object >> ~= anObject > "Answer whether the receiver and the argument do not represent the > same object." > > ^self = anObject == false > > Instead of > Object>> ~= anObject > "Answer whether the receiver and the argument do not represent the > same object." > > ^(self = anObject) not. > > Is there any particular reason for this that I'm missing? > > Performance. > > > Levente > > Thanks in advance! > -- > > "*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 > > > > > > -- > Mariano > http://marianopeck.wordpress.com > -- _,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;: Alexandre Bergel http://www.bergel.eu ^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;.

Oct. 12, 2011

Re: [Pharo-project] About ~= and ~~

by Sven Van Caekenberghe

On 12 Oct 2011, at 18:21, Mariano Martinez Peck wrote: > I would like so.... but I would like that a real hacker tell me whether I am correct or not. You most definitively are a real hacker ! Sven

Oct. 12, 2011

Re: [Pharo-project] About ~= and ~~

by Mariano Martinez Peck

On Wed, Oct 12, 2011 at 6:00 PM, Clara Allende <clari.allende(a)gmail.com>wrote: > Ok, now I get it :D Thanks a lot Mariano! > > No problem :) > > On 12 October 2011 12:49, Mariano Martinez Peck <marianopeck(a)gmail.com>wrote: > >> >> >> On Wed, Oct 12, 2011 at 5:38 PM, Levente Uzonyi <leves(a)elte.hu> wrote: >> >>> On Wed, 12 Oct 2011, Clara Allende wrote: >>> >>> Hi guys, >>>> >>>> I'm wondering, why? >>>> >>>> ProtoObject>> ~~ anObject >>>> "Answer whether the receiver and the argument are not the same object >>>> (do not have the same object pointer)." >>>> >>>> self == anObject >>>> ifTrue: [^ false] >>>> ifFalse: [^ true] >>>> >>>> >> Hi Carla. I can think about two things. The first one, is the one Levente >> said, performance. >> If you analyze the bycode of this method, you will see that it is >> extremely fast because: >> >> 1) #== has an special associated bytecode, that is, them VM maps such >> bytecode to an specific primitive and it is directly executed. It means that >> the method #== is really never sent. >> 2) ifTrue:ifFalse: is also optimized (inlined) by the compiler. Again, it >> method is never executed and instead the compiler replace a message send >> bytecode with jump ones. >> >> Another possible reason (it may not be the case, but in another places it >> is), is to prevent VM interruption for check other processes. In summary, >> the VM checks whether it should execute another process of the queue after a >> method execution. As you know, some parts of the scheduling process is done >> at the image side. And from there we lack a way to say to the VM, "please >> execute this method without checking others processes". Hence, in a few yet >> very specific places of PRocess, Scheduler, Semaphore, etc, #== is used as a >> mean of executing something WITHOUT being interrupted. I can imagine that it >> may happen the same with #~~. So if you implement such method with a #not, >> you will indeed send a message, proving a possibilty to be interrupted. >> >> Another reasons, similar to the previous one, is that sometimes #== is >> also used as a way to avoid executing method. So..there are some methods (I >> don't remember if #allInstancesDo: or #allObjectsDo:) will loop forever >> because the loop condition would be creating objects (remember that method >> execution creates objects such as MethodContext). >> So...again, I think it may happen the same with #~~. >> >> That being said, I agree that the method deserve a GOOD comment explaining >> the reasons of such optimization. >> >> Cheers >> >> >> >>> Instead of: >>>> ProtoObject>> ~~ anObject >>>> "Answer whether the receiver and the argument are not the same object >>>> (do not have the same object pointer)." >>>> >>>> ^(self == anObject) not >>>> >>>> And why? >>>> Object >> ~= anObject >>>> "Answer whether the receiver and the argument do not represent the >>>> same object." >>>> >>>> ^self = anObject == false >>>> >>>> Instead of >>>> Object>> ~= anObject >>>> "Answer whether the receiver and the argument do not represent the >>>> same object." >>>> >>>> ^(self = anObject) not. >>>> >>>> Is there any particular reason for this that I'm missing? >>>> >>> >>> Performance. >>> >>> >>> Levente >>> >>> Thanks in advance! >>>> -- >>>> >>>> "*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 >>>> >>>> >>> >> >> >> -- >> Mariano >> http://marianopeck.wordpress.com >> >> > > > -- > > "*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 > > > -- Mariano http://marianopeck.wordpress.com

Oct. 12, 2011

Re: [Pharo-project] About ~= and ~~

by Mariano Martinez Peck

On Wed, Oct 12, 2011 at 6:02 PM, StÃ©phane Ducasse <stephane.ducasse(a)inria.fr > wrote: > Mariano please enhance the comments and publish them :) > > I would like so.... but I would like that a real hacker tell me whether I am correct or not. > Stef > > On Oct 12, 2011, at 5:49 PM, Mariano Martinez Peck wrote: > > > > > > > On Wed, Oct 12, 2011 at 5:38 PM, Levente Uzonyi <leves(a)elte.hu> wrote: > > On Wed, 12 Oct 2011, Clara Allende wrote: > > > > Hi guys, > > > > I'm wondering, why? > > > > ProtoObject>> ~~ anObject > > "Answer whether the receiver and the argument are not the same object > > (do not have the same object pointer)." > > > > self == anObject > > ifTrue: [^ false] > > ifFalse: [^ true] > > > > > > Hi Carla. I can think about two things. The first one, is the one Levente > said, performance. > > If you analyze the bycode of this method, you will see that it is > extremely fast because: > > > > 1) #== has an special associated bytecode, that is, them VM maps such > bytecode to an specific primitive and it is directly executed. It means that > the method #== is really never sent. > > 2) ifTrue:ifFalse: is also optimized (inlined) by the compiler. Again, it > method is never executed and instead the compiler replace a message send > bytecode with jump ones. > > > > Another possible reason (it may not be the case, but in another places it > is), is to prevent VM interruption for check other processes. In summary, > the VM checks whether it should execute another process of the queue after a > method execution. As you know, some parts of the scheduling process is done > at the image side. And from there we lack a way to say to the VM, "please > execute this method without checking others processes". Hence, in a few yet > very specific places of PRocess, Scheduler, Semaphore, etc, #== is used as a > mean of executing something WITHOUT being interrupted. I can imagine that it > may happen the same with #~~. So if you implement such method with a #not, > you will indeed send a message, proving a possibilty to be interrupted. > > > > Another reasons, similar to the previous one, is that sometimes #== is > also used as a way to avoid executing method. So..there are some methods (I > don't remember if #allInstancesDo: or #allObjectsDo:) will loop forever > because the loop condition would be creating objects (remember that method > execution creates objects such as MethodContext). > > So...again, I think it may happen the same with #~~. > > > > That being said, I agree that the method deserve a GOOD comment > explaining the reasons of such optimization. > > > > Cheers > > > > > > Instead of: > > ProtoObject>> ~~ anObject > > "Answer whether the receiver and the argument are not the same object > > (do not have the same object pointer)." > > > > ^(self == anObject) not > > > > And why? > > Object >> ~= anObject > > "Answer whether the receiver and the argument do not represent the > > same object." > > > > ^self = anObject == false > > > > Instead of > > Object>> ~= anObject > > "Answer whether the receiver and the argument do not represent the > > same object." > > > > ^(self = anObject) not. > > > > Is there any particular reason for this that I'm missing? > > > > Performance. > > > > > > Levente > > > > Thanks in advance! > > -- > > > > "*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 > > > > > > > > > > > > -- > > Mariano > > http://marianopeck.wordpress.com > > > > > -- Mariano http://marianopeck.wordpress.com

Oct. 12, 2011