Reading this discussion, my conclusion is that not only us are confused, but everyone is. I think therefore, that the way forward is to only expose underlying API functions, and pretty much have no intelligence at all.
At a higher level, we have two different "desires" here. You may want a monotonic clock, or you may not care. You may want high resolution, or you might not care. Which one is more important is something only you know. Therefore, we must have, at the minimum, a function that returns the highest resolution monotonic clock possible, as well as a function that returns the highest resolution system/wall clock possible. We also need ways to figure out what the resolution is of these clocks. In addition to that, you may have the requirement that the monotonic clock also should not be able to jump forward, but if I understand things correctly, most current OS's will not guarantee this. You may also have the requirement that the clock not only does not jump forward, but that it doesn't go faster or slower. Some clock implementations will speed up or slow down the monotonic clock, without jumps, to sync up with the wall clock. It seems only Unix provides a monotonic clock (CLOCK_MONOTONIC_RAW) that does not get adjusted at all. Now between all these requirements, only you know which one is more important? Do you primarily want a raw monotonic clock, and secondarily high resolution, or is the resolution more important than it being monotonic? (Because if you need a high resolution, you are usually measuring small timeframes, and the clock is more unlikely to be adjusted, for example). Since there is no obvious "A is better than B that is better than C" we first of all have to expose the underlying API's somehow, to allow people to make their own decisions. Secondly, since apparently not only python-dev, but many others as well, are a bit confused on this complex issue, I'm not sure we can provide any high-level functions that makes a best choice. As such the proposed time.monotonic() to get the monotonic clock on the various systems makes a lot of sense to me. It should get the highest resolution available on the system. Get GetTickCount64() of available on Windows, else GetTickCount(). The function could have a raw=False parameter to select between clock_gettime(CLOCK_MONOTONIC) and clock_gettime(CLOCK_MONOTONIC_RAW) on Unix, and it would get mach_absolute_time() on OS X. If no monotonic clock is available, it should raise an error.The same if you pass in raw=True and there is no monotonic clock that has no adjustments available. In the same vein, time.time() should provide the highest resolution system clock/wall clock available. We also need functions or attributes to get the resolution of these clocks. But a time.steady() that tries to get a "best case" doesn't make sense at this time, as apparently nobody knows what a best case is, or what it should be called, except that it should apparently not be called steady(). Since monotonic() raises an error if there is no monotonic clock available, implementing your own fallback is trivial in any case. //Lennart _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
