[Geany-Devel] pull request on GitHub, to add GeanyHighlightSelectedWords, into Geany Plugins

[Lex Trotman]

On 31 May 2015 at 08:05, Thomas Martitz <kugel at rockbox.org> wrote:
> Am 30.05.2015 um 03:19 schrieb Matthew Brush:
>>
>>
>> Just because it's such a trivial search algorithm, using strstr() is much
>> more simple and probably more efficient than using Scintilla's API to find
>> text, but if manual and automatic mode is supported, it would make sense to
>> share the existing code, and that beats out advantage having a redundant
>> (yet simpler/faster) routine to do same, IMO. +1 (if it's not too much
>> hassle to refactor "Mark All").
>>
>
> What makes you think naive strstr() based search is faster/more efficient
> than whatever Scintilla does?
>
> I haven't looked actually, but I'd think it does the same (probably using
> C++ strings), or something smarter like KMP mentioned in this thread or
> whatever the C++ template library provides. But I don't think it does
> anything slower than the most trivial strstr() method.

Scintilla uses its own home rolled gap buffer, not C++ strings (for
the text and styles).  For plain case sensitive "find text" it uses
the naive algorithm, but each char from the buffer is accessed by
Document::charat() which will probably inline  as its in the header
and its only a call to CellBuffer::charat() which probably won't
inline since its in the cxx file not the header and which calls
SplitVector::charat() which is in the header and may or may not inline
due to its size (15 lines).

So its almost certainly slower than strstr().

But to be able to use strstr() (or any other algorithm that needs
contiguous text) the gap needs to be closed, so a large block of text
and styles need copying, which is done by memmove() which I think uses
intrinsics if available so it probably runs at memory speed so its
fast.  But its something else that complicates comparing speeds :)

Essentially the only way to tell is to try benchmarks for a
(hopefully) representative set of cases.

Cheers
Lex

>
> Best regards.
>
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