Re: [ft-devel] benchmark of sfnt checksum recalculation

[mpsuzuki]

Here is 2nd testcases checking ca. 1900 fonts (distributed in Debian
GNU/Linux). The cumulative latency is small again, but the average
latency to recalculate the checksum is 0.84 microsec, longer
than the 1st testcase.

0.60 microsec is spent to seek to the table (tt_face_goto_table()), and
0.23 microsec is spent to mathematical work (tt_synth_sfnt_checksum()).
Even if I write faster assembly version for mathematical work,
I cannot reduce the latency to half. The reduction of the
recalculation would be important.

Considering the number of the fonts including cvt/fpgm/prep tables
(or the times to call tricky font checker, 1731), the times to
call checksum calculater (tt_get_sfnt_checksum(), 44) is small.
The table length comparison (in current implementation) before table
checksum comparison is effective to reduce the number of checksum
recalculation.

TESTCASE 2)
===========

Environment is following:
CPU:    Centrino Duo
RAM:    2GB
FreeType2 configuration:
        env \
        CFLAGS="-g3 -ggdb -p -pg -fkeep-inline-functions -DFT_DEBUG_MEMORY=7" \
        ./configure --disable-shared

Fonts:
        1916 fonts (including non-TrueType) in attached list.
        1127/1916 fonts have cvt  table
        1019/1916 fonts have fpgm table
        1071/1916 fonts have prep table

Profile result
--------------
Flat profile:

Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total           
 time   seconds   seconds    calls  us/call  us/call  name    
 26.37      0.24     0.24    20873    11.50    11.50  FT_Stream_ReadULong
 10.99      0.34     0.10   106868     0.94     0.98  FT_Stream_ReadFields
  8.79      0.42     0.08     1791    44.67    45.50  tt_face_load_hmtx
  7.69      0.49     0.07  1091109     0.06     0.06  FT_Stream_GetUShort
  5.49      0.54     0.05  1858500     0.03     0.03  FT_Stream_GetULong
  4.40      0.58     0.04   239967     0.17     1.27  Load_SBit_Range
  4.40      0.62     0.04     3124    12.80    12.80  tt_cmap4_validate
  4.40      0.66     0.04     1731    23.11    23.74  tt_face_load_kern
  4.40      0.70     0.04      182   219.78   219.78  tt_cmap12_validate
  3.30      0.73     0.03   538286     0.06     0.06  FT_Stream_EnterFrame
  3.30      0.76     0.03     1731    17.33   253.10  tt_face_load_eblc
  2.20      0.78     0.02    34692     0.58     0.60  tt_face_goto_table
  1.65      0.80     0.01   583348     0.03     0.03  ft_mem_free
  1.10      0.81     0.01   531236     0.02     0.02  FT_Stream_ExitFrame
  1.10      0.81     0.01   277428     0.04     0.04  FT_Stream_Seek
  1.10      0.82     0.01   263558     0.04     0.04  ft_mem_alloc
  1.10      0.83     0.01   247736     0.04     0.08  ft_mem_realloc
  1.10      0.84     0.01    22503     0.44     0.44  ft_service_list_lookup
  1.10      0.85     0.01     6925     1.44     1.44  FT_Get_Module
  1.10      0.86     0.01     1731     5.78     6.22  cid_get_interface
  1.10      0.88     0.01     1731     5.78    52.33  tt_face_build_cmaps
  1.10      0.89     0.01     1731     5.78    15.29  tt_face_free_eblc
  1.10      0.90     0.01     1731     5.78     5.78  tt_face_free_ps_names
  0.55      0.90     0.01   263559     0.02     0.02  ft_free
  0.55      0.91     0.01     1731     2.89     2.89  ft_close_stream_by_munmap

[snip]

  0.00      0.91     0.00     1731     0.00     0.02  tt_check_trickyness
  0.00      0.91     0.00     1731     0.00     0.00  tt_check_trickyness_family
  0.00      0.91     0.00     1731     0.00     0.02  
tt_check_trickyness_sfnt_ids

[snip]

  0.00      0.91     0.00       44     0.00     0.84  tt_get_sfnt_checksum
  0.00      0.91     0.00       44     0.00     0.23  tt_synth_sfnt_checksum
  0.00      0.91     0.00       35     0.00     0.00  tt_cmap2_validate