Speeding up text file parser (BLAST tabular format)

[H. S. Teoh via Digitalmars-d-learn]

On Mon, Sep 14, 2015 at 02:34:41PM +0000, Fredrik Boulund via Digitalmars-d-learn wrote:
> On Monday, 14 September 2015 at 14:18:58 UTC, John Colvin wrote:
> >Range-based code like you are using leads to *huge* numbers of
> >function calls to get anything done. The advantage of inlining is
> >twofold: 1) you don't have to pay the cost of the function call
> >itself and 2) often more optimisation can be done once a function is
> >inlined.
> 
> Thanks for that explanation! Now that you mention it it makes perfect
> sense.  I never considered it, but of course *huge* numbers of
> function calls to e.g. next() and other range-methods will be made.
> 
> >Because there are much better at inlining. dmd is quick to compile
> >your code and is most up-to-date, but ldc and gdc will produce
> >somewhat faster code in almost all cases, sometimes very dramatically
> >much faster.
> 
> Sure sounds like I could have more fun with LDC and GDC on my system
> in addition to DMD :).

If performance is a problem, the first thing I'd recommend is to use a
profiler to find out where the hotspots are. (More often than not, I
have found that the hotspots are not where I expected them to be;
sometimes a 1-line change to an unanticipated hotspot can result in a
huge performance boost.)

The next thing I'd try is to use gdc instead of dmd. ;-)  IME, code
produced by `gdc -O3` is at least 20-30% faster than code produced by
`dmd -O -inline`. Sometimes the difference can be up to 40-50%,
depending on the kind of code you're compiling.


T

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