gprof inaccuracy

[Scott Dudley <scott at telesoft dot com>]

pardon the intrusion if this is not the appropriate forum, but i 
couldn't find one that seemed more appropriate.

i'm attempting to optimize a program that i didn't write and with which 
i'm not too familiar.  i recompiled with the -pg flag and have been 
analyzing the output of gprof.  i'm growing frustrated by it's apparent 
inaccuracy.  can someone shed light on what i might be doing wrong?  for 
example: total runtime for a test run of the program is 4 minutes.  
gprof tells me that nearly 48% of my time is spent in the function 
getAltCostTypeId():

Flat profile:

Each sample counts as 0.01 seconds.
 %   cumulative   self              self     total
time   seconds   seconds    calls  us/call  us/call  name
47.72      2.93     2.93    17021   172.14   172.14  getAltCostTypeId

----------------------------------------------------------------------
               2.93    0.00   17021/17021       main [1]
[2]     47.7    2.93    0.00   17021             getAltCostTypeId [2]
               0.00    0.00   17021/127895      toHead [63]
----------------------------------------------------------------------

i comment out the call to getAltCostTypeId(), recompile, rerun, and it 
still takes 3 minutes, 50 seconds to complete and not the ~2 minutes 
anticipated.  how can i "accurately" identify my most costly blocks of 
code using the gnu tools?

thanks.

--

Regards,

Scott Dudley

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