On Fri, Dec 2, 2011 at 10:55 AM, Mariano Martinez Peck <
marianopeck at gmail.com> wrote:

> Thanks both. I am right to assume that if the block refers to temp vars,
> parameters, or whatever in another scope, then such solution won't work. I
> mean, if I have this example for example:
>
> | bytes result blah |
> blah := 42.
> bytes := FLSerializer serializeToByteArray: (SortedCollection sortBlock:
> [:a :b | (a + blah) > b ]).
>
> Then the 'blah' is in a different context. So the mentioned solution works
> for "clean" closures, which are "self contained". In the other cases (such
> as this example), we should serialize the whole stack. Is this correct?
>

No.  The closure implementation arranges that any and all temporary
variables accessed by the closure are directly accessible from the closure
without accessing the outer contexts.  You were there for my presentation
Mariano :)  And you understood the issue then right ? :)  Remember the
closure compiler *copies* any temporary variables that are not changed
after being closed over into a closure's copiedValues, and *moves* any
temporary variables that could be changed after being closed over into
indirection vectors, and these indirection vectors are copied into the
copied values of the closure.  But, as I just said, the receiver and method
are not copied (to save time at closure creation) since these are in the
outerContext already.  These are fetched from the outerContext when the
closure is activated.

That's the trade-off, slower closure creation and larger closures and
duplication if a closure refers to its method and receiver directly, faster
closure creation, smaller closures, less duplication and very slightly
slower activation if closures refer to their receiver and method
indirectly.  The additional trade-off is this issue; the indirect approach
entails more problems for serialization and for implementing compile-time
clean closures (since the compiler needs to create an outerContext for the
method and nil for the non-existent receiver - clean closures can't refer
to self).

Is this clear or as clear as mud?


>
> Thanks!
>
>
> On Fri, Dec 2, 2011 at 7:41 PM, Eliot Miranda <eliot.miranda at gmail.com>wrote:
>
>>
>>
>> On Fri, Dec 2, 2011 at 10:20 AM, Nicolas Cellier <
>> nicolas.cellier.aka.nice at gmail.com> wrote:
>>
>>> 2011/12/2 Martin Dias <tinchodias at gmail.com>:
>>> > Hi folks
>>> >
>>> > In Fuel, we serialize a block closure with its state, including its
>>> > outerContext. This enables to serialize a sorted collection with its
>>> > sortBlock:
>>> >
>>> > | bytes result |
>>> > bytes := FLSerializer serializeToByteArray: (SortedCollection
>>> sortBlock: [:a
>>> > :b | a > b ]).
>>> > result := FLMaterializer materializeFromByteArray: bytes.
>>> > result
>>> > addAll: #(1 2 3);
>>> > yourself.
>>> > ---> a SortedCollection(3 2 1)
>>> >
>>> > Here the problem: the byte array is huge! (800kb) because we are
>>> serializing
>>> > unneeded context for the sort block.
>>> >
>>> > We wonder how to prune it and save time and space.
>>> >
>>> > Thanks in advance
>>> > Martín
>>>
>>> In the case of such clean block, there is no need of outer context
>>> during block execution.
>>> However I don't know if implementation makes it possible to ignore the
>>> context...
>>> That's more a question directed to Eliot ;)
>>>
>>
>> Arguably there is a bug in my closure implementation, which is that both
>> the receiver and the method are fetched from the outerContext.  That's not
>> a bug which can be fixed without a new VM/image combination and may be
>> something I'll look at long-term, but is something we have to live with at
>> the moment.  This means that you *do* have to serialize the outerContext.
>>  But the outerContext is used only for the receiver and method.  So you
>> don't need to full serialize the outerContext.  In particular you don't
>> need to serialize any of the outerContext's stack contents or its sender.
>>  This needs special handling, I guess in BlockClosure, to substitute a
>> suitably reduced outerContext, but it shouldn't be hard to do.  e.g.
>>
>> BlockClosure methods for: '*Fuel-serialization'
>> outerContextForSerialization
>> ^MethodContext
>> sender: nil
>>  receiver outerContext receiver
>> method: outerContext method
>> args: #()
>>
>>
>> BlockClosure methods for: '*Fuel-serialization'
>> outerContextForSerialization
>> ^MethodContext
>>  sender: nil
>> receiver self receiver
>> method: self method
>>  args: #()
>>
>>
>>
>>> Nicolas
>>>
>>>
>>
>>
>> --
>> best,
>> Eliot
>>
>>
>>
>>
>>
>
>
> --
> Mariano
> http://marianopeck.wordpress.com
>
>
>
>
>


-- 
best,
Eliot
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