The worst Phobos template (in binderoo)

[Andrei Alexandrescu via Digitalmars-d]

On 09/14/2016 04:52 PM, Stefan Koch wrote:
> On Wednesday, 14 September 2016 at 20:24:13 UTC, Stefan Koch wrote:
>> It takes a whooping 500 milliseconds
> Ahm... I misread my performance graph
> it's 138ms for the first instanciation.
> and around 5ms for every following one.
> the total time spent on it was 500ms

(Disclaimer: I didn't run any speed tests.) By looking at the definition 
of fullyQualifiedName it seems to me we can go a long way with 
traditional optimization techniques. For example consider:

string result = join(
   map!(a => format("%s%s", a[0], a[1]))(
     zip([staticMap!(storageClassesString, parameterStC)],
       [staticMap!(fullyQualifiedName, parameters)])),

This is neat, and it's neat squared because it works during compilation, 
but at some point if the resulting code runs slowly, there's no shame in 
applying old school optimization. Instead of join/map a simple loop 
should suffice; no need to use format with "%s%s" over simple 
concatenation; array zipping may be done with simple loops too.

Same a few lines below - just replace return format("%s%s%s%s%s%s%s%s", 
...) with simple concatenation. Same goes with format("shared(%s)", 
...), format("%s(%s)", ...) etc. In casual runtime code such code is 
totally fine, but in library code we'd do good to eliminate the use of 
format (which is a mini-interpreter) if speed considerations tell us to.

The unittests seem excessive too. Yes, there is such a thing as too much 
of a good thing. And use a lot of format during compilation as well :o). 
In unittests, a bunch of static asserts may be replaced with regular 
asserts.


Andrei