Boost C++ Libraries: Ticket #7719: C++11 steady_clock is not monotonic on Win32 & OSX

status changed

viboes — Sun, 25 Nov 2012 08:40:43 GMT

status new → assigned

A steady clock is not necessarily a monotonic clock. N3128 (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3128.html) is the proposal that removed monotonic clocks and added steady clocks and includes the rationale:

    The implementation of the timeout definition necessarily depends on a steady clock, one that cannot be adjusted. A monotonic clock is not sufficient. While one could be implicit in the standard, below we make one explicit.
    Given a steady clock, the monotonic clock seems to be of marginal utility, and we replace the monotonic clock with the steady clock.

Please, let me know if there is something in the documentation that say something that doesn't conforms to the C++11 standard.

fnjordy@… — Sun, 25 Nov 2012 15:09:35 GMT

Of reference the Boost documentation defines is_steady() with the C++11 definition of is_monotonic(), MSDN provides the following:

A clock is monotonic if the value that is returned by a first call to now() is always less than or equal to the value that is returned by a subsequent call to now().

A clock is steady if it is monotonic and if the time between clock ticks is constant.

msdn.microsoft.com/en-us/library/hh874790.aspx

viboes — Wed, 28 Nov 2012 11:06:39 GMT

Replying to fnjordy@…:

Of reference the Boost documentation defines is_steady() with the C++11 definition of is_monotonic(), MSDN provides the following:

Please could you point me where in the Boost.Chrono documentation appears is_monotonic?

viboes — Wed, 28 Nov 2012 11:14:32 GMT

Replying to viboes:

Replying to fnjordy@…:

Of reference the Boost documentation defines is_steady() with the C++11 definition of is_monotonic(), MSDN provides the following:

Please could you point me where in the Boost.Chrono documentation appears is_monotonic?

Oh, I got it. The doc don't use is_monotonic but the definition corresponds.

viboes — Wed, 28 Nov 2012 11:19:06 GMT

Your proposal are not steady (following the C++11 standard definition), except maybe GetTickCount(). The problem with GetTickCount() is that it is not enough long. Do you have a suggestion?

Please, could you give me the link to the stack overflow discussion?

status changed; resolution set

viboes — Sat, 08 Dec 2012 16:11:28 GMT

status assigned → closed
resolution → invalid

milestone deleted

viboes — Sat, 08 Dec 2012 16:11:45 GMT

milestone To Be Determined