intArray := (NBExternalArray ofType: 'int').

data := intArray new: 1000.

1 to:data size do:[:i |data at:i put: i].

cache := intArray new: 50.

0 to: 4 do: [:j |

1 to: 10 do: [ :k |

cache at: (j* 10) + k put: (data at: 199 + (30 * j ) + k)] ].

But if you want to take full advantage of the performance boost NB offers, you'd write a NativeBoost function to do the cache extraction*, as I outlined last time:

MyClass class >> #createCacheOf: aSource in: aDestination

createCacheOf: aSource in: aDestination

<primitive: #primitiveNativeCall module: #NativeBoostPlugin>

"Should work on both x86 and x64, as long as sizeOf: lookups work correctly"

^ self nbCallout

function: #(void (int * aSource, int * aDestination) )

emit: [:gen :proxy :asm | |destReg srcReg tmpReg intSize ptrSize|

intSize := NBExternalType sizeOf: 'int'.

ptrSize := NBExternalType sizeOf: 'void *'.

"Only use caller-saved regs, no preservation needed"

destReg := asm EAX as: ptrSize.

srcReg := asm ECX as: ptrSize.

tmpReg := asm EDX as: intSize.

asm pop: srcReg.

asm pop: destReg.

0 to: 4 do: [ :j | 0 to: 9 do: [ :offset |

asm

"Displacement in bytes, not ptr element size :S, so we have to multiply offset by that manually :S"

mov: tmpReg with: srcReg ptr + (199 + (j * 30) + offset * intSize);

mov: destReg ptr + ((j* 10) + offset * intSize) with: tmpReg]]]

and use that;

intArray := (NBExternalArray ofType: 'int').

data := intArray new: 1000.

1 to:data size do:[:i |data at:i put: i].

cache := intArray new: 50.

MyClass createCacheOf: data in: cache.

The difference using a simple [] bench is about two orders of magnitude; 11million cache extractions per seconds for the inline assembly version, while the naive loop achieves around 110k.

Cheers,

Henry

*as: is not yet defined, could be something like:

AJx86GPRegister >> #as: aSize

^ self isHighByte

ifTrue: [ self asLowByte as: aSize ]

ifFalse: [

AJx86Registers

generalPurposeWithIndex: self index

size: aSize

requiresRex: self index > (aSize > 1 ifTrue: [7] ifFalse: [ 3])

prohibitsRex: false ]

On 09 Jun 2015, at 9:46 , Matthieu Lacaton <matthieu.lacaton@gmail.com> wrote:

Hello Henrik,

Thank you very much for your answer. However, the code you provided is some sort of assembly right ? So does it mean that I need to learn assembly to do what I want ?

I'm asking that because I don't know anything about assembly so it will take me some time to learn.

Cheers,

Matthieu

2015-06-08 19:56 GMT+02:00 Henrik Johansen <henrik.s.johansen@veloxit.no>:

> On 08 Jun 2015, at 4:41 , Matthieu Lacaton <matthieu.lacaton@gmail.com> wrote:
>
> Hello everyone,
>
> I have a small question about NativeBoost : How does the "+" operator when applied to a pointer translates into NativeBoost code ?
>
> To give a bit of context, what I want to do is to reallocate some non-contiguous bytes in memory to a buffer. Basically, I have an array of integers in a buffer and I want to copy some chunks of it in another buffer. The chunks are always the same size and the offset between each chunk is always the same too.
>
> Because a bit of actual code is easier to understand here is what I'd like to do in Pharo :
>
> ...
>
> int i, j;
> int *data = malloc(1000*sizeof(int));
> int *newData = malloc(50*sizeof(int));
>
> // Allocate initial data
> for (i = 0 ; i < 1000, i++) {
> data[i] = i;
> }
>
> //Copy desired chunks into new buffer
> for (i = 0; i < 5; i++ ) {
> memcpy( newData + j*10, data + 200 + j*30, 10*sizeof(int));
> j++;
> }
>
> free(data);

You can do relative addressing like this:
(destReg ptr: dataSize) + offsetReg + constant

So with offSetRegs containing j* 10 and j* 30, you might end up with an unrolled inner loop (barring using any fancier longer-than-int moves) like:

0 to: 9 do: [:constantOffset |
asm mov: (destReg ptr: currentPlatform sizeOfInt) + dstOffsetReg + constantOffset with: (srcReg ptr: currentPlatform sizeOfInt) + 200 + srcOffsetReg + constantOffset]

If the range of j is constant, you can just as easily unroll the whole thing in a similarly compact fashion, space and sensibilites permitting:

0 to: 4 do: [ :j | 0 to: 9 do: [ :consOffset |
asm mov: (destReg ptr: currentPlatform sizeOfInt) + (j* 10) + constOffset with: (srcReg ptr: currentPlatform sizeOfInt) + 200 + (j * 30) + constOffset]

Cheers,
Henry