[dmd-internals] Windows DMD development is now impossible

[Don Clugston]

On 10 June 2013 02:28, Walter Bright <walter at digitalmars.com> wrote:

>
> On 6/9/2013 1:32 PM, Don Clugston wrote:
>
>>
>> Yeah. 4 orders of magnitude. Our codebase at sociomantic is a bit larger
>> than Phobos + druntime, but it compiles in just a few seconds.
>> The problem is, that because of templates, the memory consumption isn't
>> linear with source size.
>>
>> dmd -unittest -o- std/algorithm
>>
>> instantiates 344150 templates. Yes 344K. More than a third of a million.
>>
>
> Wow! (How many of those are unique, rather than reusing an existing
> instantiation?)


I'm not sure. That's the number of calls to the constructor of
TemplateInstance. I don't understand the code well enough to know
if it can eventually gets merged with an existing TemplateInstance.
If so, then perhaps there's something we could do to prevent them from
getting created in the first place if they are duplicates.
Certainly there are a huge number of instantiations of things like:
hasLength, isNarrowString, isForwardRange
It seems hard to believe there would be enough types to instantiate
isNarrowString thousands of different times.


 More than the number of lines of source in the module.
> And yet there are only 1305 asserts in that module -- the tests are not
> particularly comprehensive.
>
>
-cov shows 96% coverage for std.algorithm


Yeah, my point was that for N tests, we get O(N^^2) templates instantiated.
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