>> How long does it take to do a computer simulation to check that 
>> something won't break? How complicated is the process, and how much 
>> computer time does it take?
> 
> That sort of simulation is very quick and easy, only a few hours for a 
> moderately complicated part and then you get back data about the stress 
> at every point.

Right. So not instantaneous, but not months of computer time either.

I take it there's more to it then just asking the computer "hey, will 
this break if I put 25 N through it?"

> The harder simulations are the ones where you want to actually simulate 
> some dynamic force (like your product being dropped on the floor) and 
> then of course the simulator needs to deal with collisions and 
> deformations.  These sorts of simulations can take a long time to set up 
> and run for days just to simulate a fraction of a second.

At what point does it become cheaper to just make the thing rather than 
simulate it?

>> So... corrugated? Or something.
> 
> On the one I worked on we just bolted the base of the display to the 
> car, and then had two hooks at the back half way up that hooked into the 
> car mechanics (no screws).  That way when you pulled forward on the 
> display the hooks provided the strength and stiffness, and if you pushed 
> back the hooks did nothing so you were free to bend the bottom fixing 
> points if you hit it hard enough.

Mmm, ingenious.

> It depends on the product and how critical it is, plus how many you are 
> making.  For something you are only making 1 of, like a bridge or a big 
> building, you will probably do a lot of calculations.  If you are 
> planning to make 10 million of something, you can probably just make a 
> few hundred test samples and have chance to optmise them if needed.

Well yeah, it's going to depend on how safety-critical it is. If you're 
making a coathanger, probably not much need to test it. If you're making 
a karabina... there are probably legal requirements for exhaustive testing.

>> Right. So you take an educated guess, and if the prototypes fall 
>> apart, you figure out which bit broke?
> 
> Yup, for car parts we usually have 3 rounds of prototypes before mass 
> production starts.

One thing I always wondered... You see people doing all these crash 
tests, right? So... where the hell do you get an endless supply of red 
cars to crash into things?!

>> Almost every platform known to man already has a C compiler - even if 
>> it has nothing else. The C compiler is typically the very first thing 
>> that gets built. ;-)
> 
> Someone still has to build it though in the first place.

Sure. But not the Haskell development team. ;-)

I would think it's by a cross-compiler though, yes. Indeed, some systems 
are "too small" to run a C compiler natively, so you *must* cross-compile.

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