Why is D significantly slower than C# in this instance?

[H. S. Teoh]

On Wed, Apr 12, 2023 at 07:35:29AM -0700, Ali Çehreli via Digitalmars-d wrote:
> On 4/12/23 06:24, bachmeier wrote:
> 
> > Ironic that it takes so long to do a proper performance comparison
> > when the only reason to do it is to save time.
> 
> I sometimes have the same concern for optimized builds: Will the
> number of times a program will ever be executed warrant the time lost
> on optimized builds? :)
[...]

Depends on the program and how it will be used.

For one-off shell-script replacements, the answer is no, it's not worth
the bother.  For this kind of task, what you want is fast turnaround
time: to fix bugs in the code, then once it does what it needs to, you
just get a result and that's good enough. No need to sweat it.  If the
difference in performance is 10ms per run vs. 100ms per run, who cares,
you won't even notice the difference. Waiting for 5s compiles as LDC
optimizes it to the end of the world and back to get it down to 10ms is
simply not worth it, when using dmd gives you a 2s turnaround time for
100ms runtime that you won't even notice.

For long-running compute-intensive tasks, though, the tables begin
shifting the other way. If using dmd gives you 2s turnaround times but
it takes the program 10 hours to come up with the answer vs. using ldc
with 8s compile times but the program comes up with the answer in 4
hours, then yeah, the time spent on optimization is totally worth it.

Or if you're running a high-traffic website and using dmd gives you fast
turnaround during development, but caps website performance at say 1000
requests per second, then you'd want to consider using ldc for the
production build, it will take a little bit longer but may get you to
5000 requests per second.  If your business depends on the volume of
processed requests, this would totally be a worthwhile investment.  But
if it's a low traffic website and the difference is between 1000
requests per *day* vs. 5000 requests per day, then I wouldn't bother,
dmd gives me faster turnaround and therefore faster development, and I
won't even notice the difference anyway.

It's not just about compilers, of course. The same reasoning goes for
time spent hand-optimizing your code.  If you spend 10 hours optimizing
a shell script from 100ms runs to 10ms runs, you can feel great about
yourself but in the grand scheme of things it's a waste of time. But if
10 hours of hand-optimization gets you from 1000 requests per second to
10000 requests per second on a high-traffic website that will be
continuously running for a long time, then yeah it's totally worth it.


T

-- 
Insanity is doing the same thing over and over again and expecting different results.