Re: how io.read() will return nil ?

>> You're right, I've forgot to include noop function in tests list. Here
>> are the updated timings:
>>
>> $ time lua estrbench.lua empty_upvalue 1000000000
>> 142.28 real 133.89 user 0.90 sys
>> $ time lua estrbench.lua nonempty_upvalue 1000000000
>> 174.01 real 163.54 user 1.18 sys

> These should be similar, since both involve an upvalue load and a compare of
> the same type of object.

>> local nonempty_upvalue = function()
>> local a = "nonempty"
>> return a == nonempty_string
>> end

> Was the script doing a table lookup for "nonempty_string"?

Oops. Bad search-and-replace. Sorry. Should be "empty_string".

Fixed benchmark along with new output analyzer is attached. Run as:

$ KBENCH_SCRIPT=estrbench.lua KBENCH_NUM_ITER=1000000000 ./kbench.sh 2>&1 | lua kbenchparse.lua

Analyzer output for another benchmark run with relative numbers (may be corrupted by mailer, so I had to use HTML letter, sorry):

lua
----------------------------------------------------------------------------
                name |     rel |   delta | abs / iter = ns per iteration
----------------------------------------------------------------------------
                noop | 1.0000 | 0.0000 | 107.49 / 1000000000 = 0.107490 ns
   nonempty_constant | 1.1480 | 15.9100 | 123.40 / 1000000000 = 0.123400 ns
      empty_constant | 1.2079 | 22.3500 | 129.84 / 1000000000 = 0.129840 ns
    nonempty_upvalue | 1.2148 | 23.0900 | 130.58 / 1000000000 = 0.130580 ns
       empty_upvalue | 1.2777 | 29.8500 | 137.34 / 1000000000 = 0.137340 ns
       nonempty_size | 1.2886 | 31.0200 | 138.51 / 1000000000 = 0.138510 ns
          empty_size | 1.3300 | 35.4700 | 142.96 / 1000000000 = 0.142960 ns
luajit -O
----------------------------------------------------------------------------
                name |     rel |   delta | abs / iter = ns per iteration
----------------------------------------------------------------------------
                noop | 1.0000 | 0.0000 | 14.19 / 1000000000 = 0.014190 ns
   nonempty_constant | 1.2551 | 3.6200 | 17.81 / 1000000000 = 0.017810 ns
      empty_constant | 1.2699 | 3.8300 | 18.02 / 1000000000 = 0.018020 ns
       nonempty_size | 1.8189 | 11.6200 | 25.81 / 1000000000 = 0.025810 ns
          empty_size | 1.8428 | 11.9600 | 26.15 / 1000000000 = 0.026150 ns
    nonempty_upvalue | 1.8915 | 12.6500 | 26.84 / 1000000000 = 0.026840 ns
       empty_upvalue | 1.8922 | 12.6600 | 26.85 / 1000000000 = 0.026850 ns

Alexander.