Also just tried rewriting the RB loop to not use STEP:
dim index as integer
for j as integer = 0 to iterations
for i as integer = 0 to count
'pB.UInt32(i) = pA.UInt32(i)
pB.Single(index) = pA.Single(index) //* count
index = index+4
Next
index = 0
Next
But in fact this comes in at about 55 seconds, versus 45 when using STEP 4.
On 16/5/07 11:31, "Daniel Stenning" <[EMAIL PROTECTED]> wrote:
> I just tried rerunning the test but with all the contents of the inner loop
> commented out -
>
> So in the RB PTR case:
>
> dim u as integer = Count * 4
> for j as integer = 0 to iterations
> for i as integer = 0 to u step 4
> // pB.Single(i) = pA.Single(i)
> Next
> Next
>
> And in C dylib:
>
> void copySingle (int count, float * A, float * B ) {
> int i;
> for ( i = 0; i < count ; i++ ) {
> // B[i] = A[i];
> }
> };
>
> The C dylib version went down to around 2 seconds ( I think it was less )
> While the RB version is around 19 seconds.
>
>
>
> On 16/5/07 02:21, "Daniel Stenning" <[EMAIL PROTECTED]> wrote:
>
>> Heres a simple test I did which creates simply copies 44100 floats from one
>> memoryblock to another. It does this 3000 times in order to allow timing to
>> be done.
>>
>> I did this initially to see if there is a significant performance gain from
>> using Ptr pointers to the memoryblocks to do the reads and copies, versus
>> using the memoryblock SingleValue() methods.
>>
>> Indeed there is. Using Ptr is faster.
>>
>> But out of curiosity I thought I'd see how near the performance was compared
>> to doing the core copy operation in C - using a dylib. So I wrote a quick
>> dylib with a single function:
>>
>> void copySingle (int count, float * A, float * B ) {
>> int i;
>> for ( i = 0; i < count ; i++ ) {
>> B[i] = A[i];
>> }
>> };
>>
>>
>> And then via a declare called this function 3000 times. ( passing 3000 as
>> the count argument )
>>
>> The time taken in RB using Ptr: around 45 seconds
>> And in by calling the C dylib ? : 5 seconds.
>>
>> This is on a G4 PowerBook.
>>
>> I was NOT expecting that, and that 45 second timing was even after using
>> pragmas to reduce overheads.
>>
>> I was expecting RB to be a little slower than C but not THAT much slower.
>> After all - RB is supposed to be natively compiled - thus comparable to C.
>>
>> Here is the code for the RB version:
>> ****************************************************************
>>
>> #pragma DisableAutoWaitCursor
>> #pragma DisableBackgroundTasks
>> #pragma DisableBoundsChecking
>> #pragma StackOverflowChecking false
>>
>> Dim Count As integer = 44100 -1
>> DIm iterations as integer = 3000
>>
>> // source buffer
>> Dim A as new MemoryBlock( 44100 * 4)
>>
>> // stuff A with incrementing single values
>> for i as integer = 0 to Count
>> A.SingleValue(i*4) = i
>> Next
>>
>> // target buffer
>> Dim B as new MemoryBlock( 44100 * 4)
>>
>> // use pointers for speed
>> dim pA As Ptr = A
>> dim pB as Ptr = B
>>
>> Result.Text = "Started"
>> app.DoEvents
>>
>> dim u as integer = Count * 4
>> for j as integer = 0 to iterations
>> for i as integer = 0 to u step 4
>> pB.Single(i) = pA.Single(i)
>> Next
>> Next
>>
>> Beep
>>
>> Result.Text= "FINISHED"
>>
>> *************************************
>> And here is the version that calls the C function in the dylib:
>>
>>
>> soft Declare Sub copySingle Lib LIBPATH ( c as integer, ptA as Ptr, ptB
>> as Ptr )
>>
>> Dim Count As integer = 44100
>> DIm iterations as integer = 3000
>>
>> Dim A as new MemoryBlock( 44100 * 4)
>>
>> // stuff A with incrementing single values
>> for i as integer = 0 to Count-1
>> A.SingleValue(i*4) = i
>> Next
>>
>> Dim B as new MemoryBlock( 44100 * 4)
>>
>> dim pA As Ptr = A
>> dim pB as Ptr = B
>>
>> Result.Text = "Started"
>> app.DoEvents
>>
>> dim u as integer = Count
>> for j as integer = 0 to iterations
>> copySingle( u, pA, pB )
>> Next
>>
>> Beep
>> Result.Text= "FINISHED"
>>
>>
>>
>> So - here is the 40 million dollar question - WHY is RB nearly 10 times
>> slower than C ?
>> Is this something that can and should be adressed by RS ?
>>
>>
>> _______________________________________________
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>
> Regards,
>
> Dan
>
>
>
> _______________________________________________
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>
Regards,
Dan
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