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(gprof.info)Line-by-line

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Line-by-line Profiling
======================

   `gprof''s `-l' option causes the program to perform "line-by-line"
profiling.  In this mode, histogram samples are assigned not to
functions, but to individual lines of source code.  The program usually
must be compiled with a `-g' option, in addition to `-pg', in order to
generate debugging symbols for tracking source code lines.

   The flat profile is the most useful output table in line-by-line
mode.  The call graph isn't as useful as normal, since the current
version of `gprof' does not propagate call graph arcs from source code
lines to the enclosing function.  The call graph does, however, show
each line of code that called each function, along with a count.

   Here is a section of `gprof''s output, without line-by-line
profiling.  Note that `ct_init' accounted for four histogram hits, and
13327 calls to `init_block'.

     Flat profile:
     
     Each sample counts as 0.01 seconds.
       %   cumulative   self              self     total
      time   seconds   seconds    calls  us/call  us/call  name
      30.77      0.13     0.04     6335     6.31     6.31  ct_init
     
     
     		     Call graph (explanation follows)
     
     
     granularity: each sample hit covers 4 byte(s) for 7.69% of 0.13 seconds
     
     index % time    self  children    called     name
     
                     0.00    0.00       1/13496       name_too_long
                     0.00    0.00      40/13496       deflate
                     0.00    0.00     128/13496       deflate_fast
                     0.00    0.00   13327/13496       ct_init
     [7]      0.0    0.00    0.00   13496         init_block

   Now let's look at some of `gprof''s output from the same program run,
this time with line-by-line profiling enabled.  Note that `ct_init''s
four histogram hits are broken down into four lines of source code -
one hit occurred on each of lines 349, 351, 382 and 385.  In the call
graph, note how `ct_init''s 13327 calls to `init_block' are broken down
into one call from line 396, 3071 calls from line 384, 3730 calls from
line 385, and 6525 calls from 387.

     Flat profile:
     
     Each sample counts as 0.01 seconds.
       %   cumulative   self
      time   seconds   seconds    calls  name
       7.69      0.10     0.01           ct_init (trees.c:349)
       7.69      0.11     0.01           ct_init (trees.c:351)
       7.69      0.12     0.01           ct_init (trees.c:382)
       7.69      0.13     0.01           ct_init (trees.c:385)
     
     
     		     Call graph (explanation follows)
     
     
     granularity: each sample hit covers 4 byte(s) for 7.69% of 0.13 seconds
     
       % time    self  children    called     name
     
                 0.00    0.00       1/13496       name_too_long (gzip.c:1440)
                 0.00    0.00       1/13496       deflate (deflate.c:763)
                 0.00    0.00       1/13496       ct_init (trees.c:396)
                 0.00    0.00       2/13496       deflate (deflate.c:727)
                 0.00    0.00       4/13496       deflate (deflate.c:686)
                 0.00    0.00       5/13496       deflate (deflate.c:675)
                 0.00    0.00      12/13496       deflate (deflate.c:679)
                 0.00    0.00      16/13496       deflate (deflate.c:730)
                 0.00    0.00     128/13496       deflate_fast (deflate.c:654)
                 0.00    0.00    3071/13496       ct_init (trees.c:384)
                 0.00    0.00    3730/13496       ct_init (trees.c:385)
                 0.00    0.00    6525/13496       ct_init (trees.c:387)
     [6]  0.0    0.00    0.00   13496         init_block (trees.c:408)