Re: The Case for Rust (in any system)

On 9/13/24 05:33, Paul Floyd wrote:
> 
> 
> On 13-09-24 06:17, David Chisnall wrote:
>> On 13 Sep 2024, at 02:34, Joe Schaefer <joesuf4@gmail.com> wrote:
>>>
>>> I just completed a month long project to port a C++ codebase that 
>>> used vectors for array allocations back to using C‘s calloc. For a 
>>> 15% increase in memory footprint, batch jobs that took three days to 
>>> complete now finish in 10-12 hours.
>>
>> This sounds highly dubious given that std::vector is a very thin 
>> wrapper around malloc. From your description, I would expect the same 
>> speedup with some judicial use of .reserve().
> 
> I was going to say exactly the same thing.
> 
> Considering the reply to this, another one to be plonked so that I waste 
> less time.
> 
> A+
> Paul
> 
> 
> 

Some years ago, I wrote a script to time a simple selection sort coded 
in various languages.  Here's an example of the results:

https://github.com/outpaddling/Lang-speed/blob/master/Results/coral-amd64-100000

Note: The clang array/pointer performance is currently regressed due to 
changes in the optimization parameters since clang 8.  That's why it's 
noticeably slower than GCC in these results.

https://github.com/llvm/llvm-project/issues/53205#issuecomment-2318697322

In general, I have not seen a significant difference between arrays and 
vectors in all my years running this benchmark.

This benchmark is anecdotal, as it only measures performance for one 
algorithm.  But in my experience, C++ shows marginally slower 
performance and noticeably more memory use than C.

Coming back to Rust: The results above, showing about double the runtime 
of C and C++, is the best I've seen from it.  It was taking 4x as long 
as C/C++ a few years ago.  That's one reason I don't use it.  I do 
mostly scientific computing, where runtime can be costly.  This is not 
*always* an issue in systems code, but it should be examined before 
choosing a language for a particular implementation.  The other reason 
is the impact of a Rust dependency on FreeBSD ports and pkgsrc packages: 
Frequent changes to the Rust port/package lead to long build times and 
frequent breakage of dependents.

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