[racket] How can I measure time in nanoseconds?

From: Neil Toronto (neil.toronto at gmail.com)
Date: Fri Nov 12 19:12:33 EST 2010

Jon Rafkind wrote:
> On 11/12/2010 03:58 PM, Neil Toronto wrote:
>> Eli Barzilay wrote:
>>> 5 minutes ago, Jakub Piotr Cłapa wrote:
>>>> And in the case this is still not clear ;) the inexact part is not
>>>> only about formal inexactnes but about limited timer resolution as
>>>> well. Despite the CPU clock ticking more than once each nanosecond
>>>> the procesor and OS does not really count the time this accurately.
>>>> On normal OSes I would expect microsecond accuracy at best (but that
>>>> is a guess; I didn't measure).
>>> Easy to do, just run
>>>   (- (current-inexact-milliseconds) (current-inexact-milliseconds))
>>> a few times.
>> Looping to collect 1000 differences, I consistently get a minimum of
>> 0.0009765625 milliseconds = 0.9765625 microseconds. Nice guess, Jakub.
>> I also get negative numbers, which is very weird.
> well.. left to right evaluation..


Neil T

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