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Nanosecond precision when subtracting Time objects #1771

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robin850 opened this issue Jun 27, 2014 · 1 comment
Closed

Nanosecond precision when subtracting Time objects #1771

robin850 opened this issue Jun 27, 2014 · 1 comment
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Invalid or Duplicate

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@robin850
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Hello,

When using Time#- passing a Time object, the precision is inconsistent with what MRI returns. In the following example, the nanosecond precision (9 decimals) should be used but for a strange reason, the number of digits is greater than 9. Looking at the code, this condition is met ; thus, the opMinus method is triggered so this line is as well but the number of digits returned is not the expected one:

>> time1 = Time.utc(2000, 1, 2, 23, 59, 59, Rational(999999999, 1000));
>> time2 = Time.utc(2000, 1, 2, 0, 0, 0, Rational(1, 1000));

>> (time1.nsec - time2.nsec) / 1000000000.0
=> 0.999999998 # Expected result
>> diff = time1 - time2;
>> diff - diff.floor
=> 0.9999999979918357

This has been tested with JRuby 1.7.13. A RubySpec should be added here ; even if the problem is not exactly the same, the spec should fit.

Have a nice day.
@rjnienaber
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The output seems to be identical for most current ruby versions:

ruby 1.9.3p550 (2014-10-27) [x86_64-darwin14.5.0]
0.999999998
0.9999999979918357

ruby 2.2.4p230 (2015-12-16 revision 53155) [x86_64-darwin14]
0.999999998
0.9999999979918357

ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-darwin14]
0.999999998
0.9999999979918357

jruby 1.7.24 (1.9.3p551) 2016-01-20 bd68d85 on Java HotSpot(TM) 64-Bit Server VM 1.8.0_51-b16 +jit [darwin-x86_64]
0.999999998
0.9999999979918357

jruby 9.0.5.0 (2.2.3) 2016-01-26 7bee00d Java HotSpot(TM) 64-Bit Server VM 25.51-b03 on 1.8.0_51-b16 +jit [darwin-x86_64]
0.999999998
0.9999999979918357

@kares kares added this to the Invalid or Duplicate milestone Jan 17, 2017
@kares kares closed this as completed Jan 17, 2017
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@kares @robin850 @rjnienaber