Re: [Csnd-dev] [EXTERNAL] Re: [Csnd-dev] Parallel Csound performance

I did a little work on this and replaced the lock-based barrier (which seemed heavy to me) by a lightweight lock-free one.
Now I am getting some interesting results. Xanadu, which seems to be a good test case, runs like this

single-threaded: 0.78s
8 threads: 0.37s

out of the box. I checked the outputs (as usual) and the waveforms are identical.
========================
Prof. Victor Lazzarini
Maynooth University
Ireland

> On 29 Oct 2025, at 23:36, Victor Lazzarini <[email protected]> wrote:
> 
> yes, it is running correctly. Output waveforms are the same.
> ========================
> Prof. Victor Lazzarini
> Maynooth University
> Ireland
> 
>> On 29 Oct 2025, at 23:12, Steven Yi <[email protected]> wrote:
>> 
>> I'd be careful about it running fast but incorrectly. That's always
>> been my concern with ParCS is correctness.
>> 
>> On Wed, Oct 29, 2025 at 6:22 PM Victor Lazzarini
>> <[email protected]> wrote:
>>> 
>>> No, I don't think we ever disabled it. There were some questions about re-enabling some analysis to the parser (which existed in parser 2) but beyond that we never touched it.
>>> 
>>> I continued to build with it but had not been actively testing the code. I am surprised at how well it run without any changes.
>>> 
>>> best
>>> Prof. Victor Lazzarini
>>> Maynooth University
>>> Ireland
>>> 
>>>> On 29 Oct 2025, at 22:14, Steven Yi <[email protected]> wrote:
>>>> 
>>>> *Warning*
>>>> 
>>>> This email originated from outside of Maynooth University's Mail System. Do not reply, click links or open attachments unless you recognise the sender and know the content is safe.
>>>> 
>>>> This is odd, as I thought cspar was disabled in Csound?
>>>> 
>>>>> On Wed, Oct 29, 2025 at 6:08 PM Victor Lazzarini
>>>>> <[email protected]> wrote:
>>>>> 
>>>>> I’m back investigating parallel Csound performance and it was interesting to see that
>>>>> Csound 7 is working well with it, in fact far better than 6.18.
>>>>> 
>>>>> Running 1000 oscillator instrs for 60 secs I got these stats
>>>>> 
>>>>> ksmps = 100
>>>>> -----------
>>>>> single thread: 3.9s
>>>>> 8 threads: 3.9s
>>>>> 
>>>>> ksmps = 150
>>>>> ----------
>>>>> single thread: 3.5s
>>>>> 8 threads: 2.7s
>>>>> 
>>>>> ksmps = 300
>>>>> ----------
>>>>> single thread: 3.2s
>>>>> 8 threads: 1.6s
>>>>> 
>>>>> ksmps = 500
>>>>> ----------
>>>>> single thread: 3.2s
>>>>> 8 threads: 1.2s
>>>>> 
>>>>> ksmps = 1000
>>>>> ----------
>>>>> single thread: 3.3s
>>>>> 8 threads: 0.8
>>>>> 
>>>>> In comparison with 6.18 the last test ran at 11secs for 8 threads. In fact, 6.18 was always slower in parallel
>>>>> performance. Something was very broken there. Single-threaded performance is on a par with Csound 7.
>>>>> 
>>>>> I can only think the new parser is working better with the parallel dispatch, or that something else was wrong
>>>>> in the 6.x and got fixed in 7. Anyway, I am pleased with these results. In general, ksmps=100 seems to be the break even
>>>>> point, below that multi-threaded performance is always losing. Also ksmps=1000 is more or less the highest gain,
>>>>> with diminishing returns after that. In my computer, 8 threads seem to be the optimal.
>>>>> 
>>>>> best
>>>>> ========================
>>>>> Prof. Victor Lazzarini
>>>>> Maynooth University
>>>>> Ireland
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>