Menu
▾
▴
Re: [xmlvm-users] Arrays manipulation on iPhone
|
From: Jacob N. <jac...@gm...> - 2009-09-21 09:07:49
|
Hi Arno and Kevin,
thanks for your great replies.
As Objective-C and its classes are new to me (as well as XMLVM) another
possibility just occured to me - converting "my" extra time spending into
money and paying you guys (or someone you know and trust), the money for
improving XMLVM.
Thas is, a months salary or so, for making these improvements in a way that
allows us to use arrays of simple types with more or less the performance in
we have in Java.
I would love to contribute somehow to this open source project, and perhaps
you know someone who would like to get more involved, and already knows
XMLVM and Objective-C ?
Yours,
Jacob
2009/9/21 Jacob Nordfalk <jac...@gm...>
> Hello Sascha,
>
> thanks for your quick reply.
>
> In our case the hope was to use 170 hours on preparing and porting our Java
> code, withing one calendar month.
> We have now changed that estimate to the double - 340 hours, within 1 1/2
> calendar month.
>
> We are proficient Java coders (Objective-C is new, but for array
> manopulations it probably wouldnt seem to give too much headache :-) and one
> (I) has understanding of XML, bytecode and virtual machines. I could
> allocate up to 60 hours for improving XMLVM during the next month if that
> could solve our problems.
>
> I know 60 hours isnt much, but as economy is a concern here must weight it
> against finding another way of porting the application (eventually by hand).
> If you, within these time contraint, would recommend spending some time
> improving XMLVM and your'e willing to guide me and engage yourselves in the
> project too, then lets consider it.
>
> However, it seems to me that there is another performance problem here, and
> that is the usage of NSMutableArray of objects instead of a byte[] array ?
>
> I would be very thankfull if you could comment with your best guess on,
> whether the factor 20 somes from the stack-based model used for generating
> Objective-C code, or from the usage of NSMutableArray of objects instead of
> byte[] arrays?
>
> Another important questions is then: How much effort would be required to
> make a version of XMLVM that generated code using arrays of simple type
> instead of arrays ?
>
> Thank you,
> Jacob
>
> 2009/9/21 Sascha Haeberling <sa...@xm...>
>
> Hello Jacob,
>> thank you for your great analysis and question.
>>
>> You are absolutely right. As you can see, we are trying to mimic a JVM as
>> close as possible. While we think that the performance is fine for most use
>> cases, some use cases (like yours) can actually perform much worse when
>> being cross-compiled with XMLVM. Therefore, one of our current tasks is to
>> look at converting our stack-bases model to a register-based one, so that
>> languages like Objective-C can benefit.
>>
>> However, we are still in the planning stage of this and I cannot give you
>> any deadlines. Would this be something you are interested in contributing to
>> or do you have any other ideas?
>>
>> Thank you
>> // Sascha
>>
>> On Sun, Sep 20, 2009 at 11:29 PM, Jacob Nordfalk <
>> jac...@gm...> wrote:
>>
>>> Hi,
>>>
>>> I am considering porting an image manipulation program in Java to iPhone
>>> using XMLVM.
>>>
>>> However, code such as
>>>
>>> public byte[] xxx(byte[] rgb) {
>>>
>>> for (int i = 0; i<rgb.length; i+=3) {
>>> rgb[i] += 1;
>>> rgb[i+1]/=2;
>>> rgb[i+2]/=2;
>>> }
>>>
>>> return rgb;
>>> }
>>>
>>> seems to run 20 times slower than JIT-enabled Java when compiling xmlvm
>>> generated objective-C.
>>>
>>> When I looked at the code I understood why - the generated objective-C is
>>> something like 26 lines
>>> per line of Java (here below is for the line: rgb[i+1]/=2).
>>>
>>>
>>> - (NSMutableArray*) optimize___byte_ARRAYTYPE :(NSMutableArray*)n1
>>> {
>>> XMLVMElem _stack[4];
>>> XMLVMElem _locals[5];
>>> int _sp = 0;
>>> XMLVMElem _op1, _op2, _op3;
>>> ...
>>>
>>> *// rgb[i+1]/=2;*
>>> _stack[_sp++].o = _locals[1].o;
>>> _op1.i = _locals[4].i;
>>> _stack[_sp++].i = _op1.i;
>>> _stack[_sp++].i = 1;
>>> _op2.i = _stack[--_sp].i;
>>> _op1.i = _stack[--_sp].i;
>>> _stack[_sp++].i = _op1.i + _op2.i;
>>> _op1 = _stack[_sp - 2];
>>> _op2 = _stack[_sp - 1];
>>> _stack[_sp++] = _op1;
>>> _stack[_sp++] = _op2;
>>> _op1.i = _stack[--_sp].i;
>>> _op2.o = _stack[--_sp].o;
>>> _stack[_sp++].i = [[_op2.o objectAtIndex: _op1.i] intValue];
>>> _stack[_sp++].i = 2;
>>> _op2.i = _stack[--_sp].i;
>>> _op1.i = _stack[--_sp].i;
>>> _stack[_sp++].i = _op1.i / _op2.i;
>>> _op1.i = _stack[--_sp].i;
>>> _stack[_sp++].i = (int) (_op1.i & 0xFF);
>>> _op1.i = _stack[--_sp].i;
>>> _op2.i = _stack[--_sp].i;
>>> _op3.o = _stack[--_sp].o;
>>> [_op3.o replaceObjectAtIndex: _op2.i withObject: [NSNumber
>>> numberWithInt: _op1.i]];
>>>
>>>
>>> Now, I understand that the speed factor 20 is becaurse XMLVM is emulating
>>> the stack-based JVM in Objective-C,
>>> but I as I have really LOT of array manipulation code I am asking you:
>>>
>>>
>>> Do you have any advice or ideas on how to make Java code using simple
>>> array manipulations run relatively fast on the iPhone ?
>>>
>>>
>>>
>>> Thanks you,
>>> Jacob Nordfalk
>>>
>>> --
>>> Jacob Nordfalk
>>> एस्पेरान्तो के हो? http://www.esperanto.org.np/.
>>> Memoraĵoj de KEF -. http://kef.saluton.dk/memorajoj/
>>>
>>>
>>> ------------------------------------------------------------------------------
>>> Come build with us! The BlackBerry® Developer Conference in SF, CA
>>> is the only developer event you need to attend this year. Jumpstart your
>>> developing skills, take BlackBerry mobile applications to market and stay
>>> ahead of the curve. Join us from November 9-12, 2009. Register
>>> now!
>>> http://p.sf.net/sfu/devconf
>>> _______________________________________________
>>> xmlvm-users mailing list
>>> xml...@li...
>>> https://lists.sourceforge.net/lists/listinfo/xmlvm-users
>>>
>>>
>>
>
>
> --
> Jacob Nordfalk
> एस्पेरान्तो के हो? http://www.esperanto.org.np/.
> Memoraĵoj de KEF -. http://kef.saluton.dk/memorajoj/
>
--
Jacob Nordfalk
एस्पेरान्तो के हो? http://www.esperanto.org.np/.
Memoraĵoj de KEF -. http://kef.saluton.dk/memorajoj/
|
