[poppler] splash output improvement

[Carlos Fangmeier]

Albert Astals Cid wrote:

>A Dijous 10 Novembre 2005 19:17, Carlos Fangmeier va escriure:
>  
>
>>Hi,
>>    
>>
>Hi
>  
>
Hi again :D

>  
>
>>I'm using the evince pdf reader, who use the poppler lib to do the 
>>render. I notice that the render of poppler ( using the splash output )
>>is much slower than xdf. Maybe runing evince on a desktop pc isn'tt a
>>big deal, but runing evince on a Zaurus C860 is to slow.
>>Using valgrind-cachegrind on my pc I find out that most of the cpu used
>>for rendering a pdf, was spend in the constructor
>>SplashScreen::SplashScreen  ( almost 38% ), so I decided to do some
>>litle improvement. After my changes the cpu spend on this constructor
>>dropped to 0.1%. With this improvement the evince response was much
>>better than before.
>>Attachedt to this mail is the patch with my changes, maybe they aren't
>>100% acording with your develope, but it could  be a good idea.
>>Basically I implemented a cache for all possible threshold matrix.
>>    
>>
>
>Hmm, this is C++, so i think having 
>
>SplashCoord **cache_mat;
>int cache_count;
>
>as static members of SplashScreen would be better, what do you think?
>
>  
>
I agree, my patch isn't a nice code :$ , but it give a idea where and 
how to improve the splash output.

>Also, i don't seem to understand the caching method much, let's say we first 
>call that contructor with 100, we would get 
>
>size2 = sizeA >> 1  // size2 = 50
>size = size2 << 1; // size = 100
>
>size1 = size +1; // size1 = 101
>if( cache_count <  size1 ) // true because cache_count stats at 0
>{
>	// create a 101 SplashCoord * array
>}
>........
>  
>
Yes, thus it is how it works. It use the value of "size" as an index to 
go into the cache_mat and get the previously generated matrix.

>// end up using only the 100 position of that array, all else is empty
>  
>
The gain in speed was much better than the loose of that unused position 
in the array.

>So would be better to just use a GooHash and not loose the other positions?
>  
>
>My other concern would be cache growing too much as you never seem to empty it 
>and that making it take too much mem but 
>
>$ grep -ri "new SplashScreen" *
>splash/SplashScreen.h:  SplashScreen *copy() { return new 
>SplashScreen(this); }
>splash/SplashState.cc:  screen = new SplashScreen(10);
>
>says that we always use 10 as size for the SplashScreen so the cache is always 
>going to be of 1 element :-D
>  
>
When I tested my patch, I dind't looked for all the places where one 
"new SplashScreen" was, but I saw that the value of size was allways 10, 
but I didn't know that this was the only value it would take. What is 
the meaning of this magic number?

>So can you try to rewrite the patch using a static GooHash as SplashScreen 
>member and see if it still works/gives you the same quickness?
>  
>
Thanks for the advice, I will look for it in the code, rewrite my code 
and test it again. I let you know the results.

>Thanks.
>
>  
>
Thanks you.

>Albert
>
>
>  
>
Carlos

>>Best regards
>>
>>
>>Carlos Fangmeier
>>
>>
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