Study: build times for D programs

[Jonathan M Davis]

On Wednesday, July 25, 2012 22:53:08 Rainer Schuetze wrote:
> On 25.07.2012 19:24, Walter Bright wrote:
> > On 7/25/2012 8:13 AM, Andrei Alexandrescu wrote:
> >> Yes, and both debug and release build times are important.
> > 
> > Optimized build time comparisons are less relevant - are you really
> > willing to trade off faster optimization times for less optimization?
> > 
> > I think it's more the time of the edit-compile-debug loop, which would
> > be the unoptimized build times.
> 
> The "edit-compile-debug loop" is a use case where the D module system
> does not shine so well. Compare build times when only editing a single
> source file:
> With the help of incremental linking, building a large C++ project only
> takes seconds.
> In contrast, the D project usually recompiles everything from scratch
> with every little change.

D should actually compile _faster_ if you compile everything at once - 
certainly for smaller projects - since it then only has to lex and parse each 
module once. Incremental builds avoid having to fully compile each module 
every time, but there's still plenty of extra lexing and parsing which goes 
on.

I don't know how much it shifts with large projects (maybe incremental builds 
actually end up being better then, because you have enough files which aren't 
related to one another that the amount of code which needs to be relexed a 
reparsed is minimal in comparison to the number of files), but you can do 
incremental building with dmd if you want to. It's just more typical to do it 
all at once, because for most projects, that's faster. So, I don't see how 
there's an complaint against D here.

- Jonathan M Davis