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[Bug translator/5019] New: histograms don't handle negative numbers properly


Both the hist_log and hist_linear extractors print bogus data when negative
numbers have been fed to an aggregation. Are histograms supposed to handle
negative numbers?  BTW, the integer extractors work as expected.

Examples:

The following script:

global stat
probe begin {
        stat <<< 1
        stat <<< -20
        stat <<< 300
        stat <<< -5000
        print(@hist_log(stat))
        exit()
}

yields this output:

               value |-------------------------------------------------- count
                   0 |                                                   0
                   1 |@                                                  1
                   2 |                                                   0
                   4 |                                                   0
                   8 |                                                   0
                  16 |                                                   0
                  32 |                                                   0
                  64 |                                                   0
                 128 |                                                   0
                 256 |@                                                  1
                 512 |                                                   0
                1024 |                                                   0
                2048 |                                                   0
                4096 |                                                   0
                8192 |                                                   0
               16384 |                                                   0
               32768 |                                                   0
               65536 |                                                   0
              131072 |                                                   0
              262144 |                                                   0
              524288 |                                                   0
             1048576 |                                                   0
             2097152 |                                                   0
             4194304 |                                                   0
             8388608 |                                                   0
            16777216 |                                                   0
            33554432 |                                                   0
            67108864 |                                                   0
           134217728 |                                                   0
           268435456 |                                                   0
           536870912 |                                                   0
          1073741824 |                                                   0
          2147483648 |                                                   0
          4294967296 |                                                   0
          8589934592 |                                                   0
         17179869184 |                                                   0
         34359738368 |                                                   0
         68719476736 |                                                   0
        137438953472 |                                                   0
        274877906944 |                                                   0
        549755813888 |                                                   0
       1099511627776 |                                                   0
       2199023255552 |                                                   0
       4398046511104 |                                                   0
       8796093022208 |                                                   0
      17592186044416 |                                                   0
      35184372088832 |                                                   0
      70368744177664 |                                                   0
     140737488355328 |                                                   0
     281474976710656 |                                                   0
     562949953421312 |                                                   0
    1125899906842624 |                                                   0
    2251799813685248 |                                                   0
    4503599627370496 |                                                   0
    9007199254740992 |                                                   0
   18014398509481984 |                                                   0
   36028797018963968 |                                                   0
   72057594037927936 |                                                   0
  144115188075855872 |                                                   0
  288230376151711744 |                                                   0
  576460752303423488 |                                                   0
 1152921504606846976 |                                                   0
 2305843009213693952 |                                                   0
 4611686018427387904 |@@                                                 2


And the following script with hist_linear():

global stat

probe begin {
        stat <<< 1
        stat <<< -20
        stat <<< 300
        stat <<< -5000
        print(@hist_linear(stat, , 1024000000, 102400000))
        exit()
}

yields this result:

    value |-------------------------------------------------- count
        0 |@@@@                                               4
102400000 |                                                   0
204800000 |                                                   0

-- 
           Summary: histograms don't handle negative numbers properly
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: mmlnx at us dot ibm dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=5019

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