About ~= and ~~

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?

... [show rest of quote]

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

On Wed, Oct 12, 2011 at 5:38 PM, Levente Uzonyi <[hidden email]> 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?

... [show rest of quote]

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

... [show rest of quote]

--
Mariano
http://marianopeck.wordpress.com

Mariano please enhance the comments and publish them :)

Stef

On Oct 12, 2011, at 5:49 PM, Mariano Martinez Peck wrote:

>
>
> On Wed, Oct 12, 2011 at 5:38 PM, Levente Uzonyi <[hidden email]> 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
>

Ok, now I get it :D Thanks a lot Mariano!

On 12 October 2011 12:49, Mariano Martinez Peck <[hidden email]> wrote:

On Wed, Oct 12, 2011 at 5:38 PM, Levente Uzonyi <[hidden email]> 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?

... [show rest of quote]

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

... [show rest of quote]

--
Mariano
http://marianopeck.wordpress.com

... [show rest of quote]

--

"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

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?

... [show rest of quote]

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

 

On Wed, Oct 12, 2011 at 8:38 AM, Levente Uzonyi <[hidden email]> 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?

... [show rest of quote]

Performance.

... [show rest of quote]

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

 

On Wed, Oct 12, 2011 at 6:44 PM, Eliot Miranda <[hidden email]> wrote:

 

On Wed, Oct 12, 2011 at 8:38 AM, Levente Uzonyi <[hidden email]> 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?

... [show rest of quote]

Performance.

... [show rest of quote]

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?

 

... [show rest of quote]

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

... [show rest of quote]

--
Mariano
http://marianopeck.wordpress.com

 

On Wed, Oct 12, 2011 at 10:26 AM, Mariano Martinez Peck <[hidden email]> wrote:

 

On Wed, Oct 12, 2011 at 6:44 PM, Eliot Miranda <[hidden email]> wrote:

 

On Wed, Oct 12, 2011 at 8:38 AM, Levente Uzonyi <[hidden email]> 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?

... [show rest of quote]

Performance.

... [show rest of quote]

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?

 

... [show rest of quote]

with or without special bytecode associated?

... [show rest of quote]

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

... [show rest of quote]

--
Mariano
http://marianopeck.wordpress.com

... [show rest of quote]

--
best,

Eliot

On Wed, Oct 12, 2011 at 7:29 PM, Eliot Miranda <[hidden email]> wrote:

 

On Wed, Oct 12, 2011 at 10:26 AM, Mariano Martinez Peck <[hidden email]> wrote:

 

On Wed, Oct 12, 2011 at 6:44 PM, Eliot Miranda <[hidden email]> wrote:

 

On Wed, Oct 12, 2011 at 8:38 AM, Levente Uzonyi <[hidden email]> 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?

... [show rest of quote]

Performance.

... [show rest of quote]

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?

 

... [show rest of quote]

with or without special bytecode associated?

... [show rest of quote]

Initially without.  

... [show rest of quote]

+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

... [show rest of quote]

--
Mariano
http://marianopeck.wordpress.com

... [show rest of quote]

--
best,

Eliot

... [show rest of quote]

--
Mariano
http://marianopeck.wordpress.com

On Thu, 13 Oct 2011, Igor Stasenko wrote:

On 12 October 2011 23:22, Levente Uzonyi <[hidden email]> wrote:

On Wed, 12 Oct 2011, Mariano Martinez Peck wrote:

On Wed, Oct 12, 2011 at 5:38 PM, Levente Uzonyi <[hidden email]> 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.

... [show rest of quote]

I don't see how this would be a reason. When you send #~~, then you
explicitly allow a suspension point, so not using #not won't avoid
suspension points.

... [show rest of quote]

To my thinking, in a first place, i would ask:
why instead of fixing the code which may be affected by having or not
suspension points,
we introducing new workarounds ??

... [show rest of quote]

Which code needs to be fixed?

I think it is bad excuse for introduction of new primitive.
If we miss some atomicity for semaphores, lets add a primitive(s)
which fixing the semaphore issue(s).

Are there any issues with semaphores?

But introducing new primitive to avoid suspension?!?!  i cannot follow
this line of thinking.

I guess you're not replying to my mail, but Eliot's. Btw there's no such "line of thinking". He didn't add the primitive for #~~ to avoid a suspension point, but to improve it's performance.

Levente

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

#allInstancesDo: uses primitives to avoid the problem. #allObjectsDo: uses a
custom marker object, so creating new objects won't cause infinite loop
(because gc doesn't change the order of any two objects).

the loop condition would be creating objects (remember that method
execution
creates objects such as MethodContext).

Contexts object are not created until requested and these loops don't need
contexts. Some old methods interating through all/some objects use 0 as the
marker object. These may have problems with objects created during their
loops.


Levente

... [show rest of quote]

--
Best regards,
Igor Stasenko.

... [show rest of quote]