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From: Malcolm McLean <malcolm.arthur.mclean@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: Baby X is bor nagain
Date: Mon, 17 Jun 2024 22:06:35 +0100
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On 17/06/2024 20:29, David Brown wrote:
> On 17/06/2024 21:17, Malcolm McLean wrote:
>> On 17/06/2024 17:21, David Brown wrote:
>>> On 17/06/2024 17:48, Malcolm McLean wrote:
>>>>
>>> Using C without optimisation is like driving a car but refusing to go 
>>> out of first gear.  You would probably have been better off with a 
>>> bicycle or driving a tank, according to the task at hand.
>>>
>> I drive C in first gear when I'm developing, which means that the car 
>> is given instructions to go to the right place and obey all, the rules 
>> of the road.
> 
> I do my C development with optimisations enabled, which means that the C 
> compiler will obey all the rules and requirements of C.  Optimisations 
> don't change the meaning of correct code - they only have an effect on 
> the results of your code if you have written incorrect code.  I don't 
> know about you, but my aim in development is to write /correct/ code. If 
> disabling optimisations helped in some way, it would be due to bugs and 
> luck.
> 
>> But it never gets out of frst gear when I'm driving it. However 
>> because of the nature of what we do, which is interactivce programming 
>> mostly, usually "just noticeable" time is sufficient. It's a bit like 
>> driving in London - a top of the range sports car is no better than a 
>> beat up old mini, they travel at the same speed because of all the 
>> interactions.
>>
> 
> If I am writing PC code where the timing is determined by user 
> interaction, I would not be writing in C - it is almost certainly a poor 
> choice of language for the task.
> 
>> They I had it over to the deployment team, and they take the 
>> restraints off, and allow it to go up to top gear, and it is compiled 
>> with full optimisation. 
> 
> That is insane development practice, if I understand you correctly.  For 
> some kinds of development work, it can make sense to have one person (or 
> team) make prototypes or proofs-of-concept, and then have another person 
> (or team) use that as a guide, specification and test comparison when 
> writing a fast implementation for the real product.  But the prototype 
> should be in a high-level language, written in the clearest and simplest 
> manner - not crappy code in a low-level language that works by luck when 
> it is not optimised!
> 
>> And I don't actually have a computer with one of the most important 
>> hardware targets, but it's all written in C++, a bit in C, and none in 
>> assembler. So I can't profile it, and I have to rely on insight into 
>> where the inner loop will be, and how to avoid expensive operations in 
>> the inner loop.
> 
> If you are writing C++ and are not happy about using optimisation, you 
> are in the wrong job.
> 
You know what hardware your code will run on. I don't.

-- 
Check out my hobby project.
http://malcolmmclean.github.io/babyxrc