[GHC] #10111: hp2ps silently discards samples

[GHC]

#10111: hp2ps silently discards samples
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              Reporter:  ezyang      |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Profiling   |           Version:  7.11
              Keywords:              |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  Incorrect result
  Unknown/Multiple                   |  at runtime
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
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 Consider the following hp file:

 {{{
 JOB "whatever"
 DATE "Sat Feb 21 12:56 2015"
 SAMPLE_UNIT "seconds"
 VALUE_UNIT "bytes"
 BEGIN_SAMPLE 0.00
 MAIN    1000
 END_SAMPLE 0.00
 BEGIN_SAMPLE 0.00
 MAIN    100
 END_SAMPLE 0.00
 BEGIN_SAMPLE 0.01
 MAIN    500
 END_SAMPLE 0.01
 }}}

 hp2ps will generate a graph showing heap usage going from 100 bytes to 500
 bytes... not 1000-100-500 as expected. This is because hp2ps only uses the
 last sample with the same timestamp.

 These hp files show in practice because GHC doesn't output BEGIN_SAMPLE
 entries with enough precision, see also
 https://phabricator.haskell.org/D679 to increase the precision.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10111>
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