Re: [Groff] caching result of charinfo::get_flags

[Werner LEMBERG]

> BTW, I've just used the file `bash.1' version 2.05 from the linuxjm
> project (with 217kByte it is about 30 times larger than `gprof.1'),
> and profiling shows a completely different hot spot:
> 
>   %   cumulative   self              self     total           
>  time   seconds   seconds    calls  ms/call  ms/call  name    
>  43.14      0.22     0.22    78453     0.00     0.00  
> unicode_decompose_ptable::lookup
>   5.88      0.25     0.03   695361     0.00     0.00  token::next
>   5.88      0.28     0.03     9941     0.00     0.00  file_iterator::fill
>   3.92      0.30     0.02   202744     0.00     0.00  tfont::get_width
>   3.92      0.32     0.02   108869     0.00     0.00  read_long_escape_name
>   ...

I've a bit experimented and tried the `improved' hash function given
in 

  http://www.haible.de/bruno/hashfunc.html

However, this increases the hash collisions enormously, making the
program slower by a large amount.  It seems that I had to manually
taylor a good hash function, but I fear that I'm not talented (and
interested) enough to do so...

Instead, I tried this patch


--- ptable.h.old        2010-12-21 13:37:21.000000000 +0100
+++ ptable.h    2010-12-21 13:41:44.000000000 +0100
@@ -86,7 +86,7 @@
   unsigned size;                                                             \
   unsigned used;                                                             \
   enum {                                                                     \
-    FULL_NUM = 3,                                                            \
+    FULL_NUM = 1,                                                            \
     FULL_DEN = 4,                                                            \
     INITIAL_SIZE = 17                                                        \
   };                                                                         \


to reduce the filling of the hash table, increasing the number of
empty slots by a large amount, and now I get this:

  %   cumulative   self              self     total
 time   seconds   seconds    calls  ms/call  ms/call  name
 11.11      0.04     0.04   336788     0.00     0.00  hunits::hunits
  8.33      0.07     0.03   825834     0.00     0.00  get_copy
  8.33      0.10     0.03   695361     0.00     0.00  token::next
  8.33      0.13     0.03   300089     0.00     0.00  check_unicode_name
  5.56      0.15     0.02   290504     0.00     0.00  symbol::symbol
  5.56      0.17     0.02    78453     0.00     0.00  
unicode_decompose_ptable::lookup

According to valgrind, while testing the Japanese `bash.1' man page,
the additional amount of allocated memory is less than 200kByte; I
think this increase of memory is a neglegible today...

Note that the stuff in ptable.h is not used for the normal groff
symbol dictionary lookup and the like.

Opinions, please.


   Werner