NativeBoost : optimisation of the machine code generation

Hi everyone,

I'm trying to reduce the computation time of the following pseudo-code:

- memory allocation (~40 doubles)

- object heap to C heap copying

- NativeBoost call (nbCall:)

- memory freeing

The time profiling results are bellow:

- 24*3600 calls : > 1 minute

- 24*3600 calls with only memory allocation and copying : < 1 second

- 1 call with a 24*3600 loop inside de C code : < 1 second

So it appears that the very coslty step is the transition from Pharo to C. And I was wondering if it was possible to drasticly reduce this time by doing something like, generate the the machine code once and call it multiple time ?

Thanks in advance !

Thomas.

I think that if you posted the code , preferably that contains only the problem would be easier to test , debug and investigate. 

On Thu, Aug 7, 2014 at 6:25 PM, Thomas Bany <[hidden email]> wrote:

Hi everyone,

I'm trying to reduce the computation time of the following pseudo-code:

- memory allocation (~40 doubles)

- object heap to C heap copying

- NativeBoost call (nbCall:)

- memory freeing

The time profiling results are bellow:

- 24*3600 calls : > 1 minute

- 24*3600 calls with only memory allocation and copying : < 1 second

- 1 call with a 24*3600 loop inside de C code : < 1 second

So it appears that the very coslty step is the transition from Pharo to C. And I was wondering if it was possible to drasticly reduce this time by doing something like, generate the the machine code once and call it multiple time ?

Thanks in advance !

Thomas.

@ Alexandre: sure, no problem !

@ Luc:

I'm not sure how much code I can provide without being to specific, but here is how it goes :

• Let's say I have the Smalltalk code bellow:

MyClass>>withNBCall

   externalArray := NBExternalArrayOfDoubles new: self internalArray size.

   output := NBExternalArrayOfDoubles new: 4.

   [self actualNBCallWith: externalArray adress storeResultIn: output adress] ensure: [externalArray free. output free].

MyClass>>withNBCallCommented

   externalArray := NBExternalArrayOfDoubles new: self internalArray size.

   output := NBExternalArrayOfDoubles new: 4.

   ["self actualNBCallWith: externalArray adress storeResultIn: output adress"] ensure: [externalArray free. output free].

MyClass>>actualNBCallWith: externalArray storeResultIn: output
   <primitive: 'primitiveNativeCall' module: 'NativeBoostPlugin' error: errorCode>

   ^self nbCall: #(void callToC(double * externalArray, double * output)) module: 'lib/myModule.dll'

• And the C code bellow:

void callToC(double * externalArray, double * output) {

   computationWith(externalArray, output);

}

void specialCallToC(double * externalArray, double * output) {

   unsigned int i;

   for (i = 0; i < 24*3600; i++)

      computationWith(externalArray, output);

}

• Now I have the following code typed in Time Profiler tool :

object := (MyClass new) variousInitialization; yourself

24*3600 timesRepeat: [object withNBCall]

>> Over 1 minute computation time of which over 99% are primitives. Also I don't see the nbCall: in the tree.

object := (MyClass new) variousInitialization; yourself

24*3600 timesRepeat: [object withNBCallCommented]

>> Less than 1 second.

object := (MyClass new) variousInitialization; yourself

object withNBCall

>> Less than 1 millisecond.

object := (MyClass new) variousInitialization; yourself

object withNBSpecialCall "This time, I use the specialCallToC() function"

>> Arround 20 millisecond.

Allright, that's a pile of code but I hope it help :)

On a side note:

• Pharo 3, Win 7 32-bit
  
• I'm not at work anymore and don't have my code with me. So I will double check tomorow that I didn't provided false informations but I think it's accurate of what I do.

Again, thanks for the interest on my issue !

Thomas.

2014-08-07 18:39 GMT+02:00 kilon alios <[hidden email]>:

I think that if you posted the code , preferably that contains only the problem would be easier to test , debug and investigate. 

On Thu, Aug 7, 2014 at 6:25 PM, Thomas Bany <[hidden email]> wrote:

Hi everyone,

I'm trying to reduce the computation time of the following pseudo-code:

- memory allocation (~40 doubles)

- object heap to C heap copying

- NativeBoost call (nbCall:)

- memory freeing

The time profiling results are bellow:

- 24*3600 calls : > 1 minute

- 24*3600 calls with only memory allocation and copying : < 1 second

- 1 call with a 24*3600 loop inside de C code : < 1 second

So it appears that the very coslty step is the transition from Pharo to C. And I was wondering if it was possible to drasticly reduce this time by doing something like, generate the the machine code once and call it multiple time ?

Thanks in advance !

Thomas.

NativeBoost methods compiles native code only once (the first time they are executed) and when sessionId changes (because you may be on a different platform).
So this is already like that. The assembly code is cached in the method literal.

Stef

On 7/8/14 17:25, Thomas Bany wrote:

Hi everyone,

I'm trying to reduce the computation time of the following pseudo-code:

- memory allocation (~40 doubles)
- object heap to C heap copying
- NativeBoost call (nbCall:)
- memory freeing

The time profiling results are bellow:

- 24*3600 calls : > 1 minute
- 24*3600 calls with only memory allocation and copying : < 1 second
- 1 call with a 24*3600 loop inside de C code : < 1 second

So it appears that the very coslty step is the transition from Pharo to C. And I was wondering if it was possible to drasticly reduce this time by doing something like, generate the the machine code once and call it multiple time ?

Thanks in advance !

Thomas.