Experimental Physics and
Industrial Control System

Michael Davidsaver via Core-talk <core-talk at aps.anl.gov> · Tue, 4 Aug 2020 09:14:22 -0700

On 8/4/20 9:09 AM, Johnson, Andrew N. wrote:
> On Aug 3, 2020, at 9:37 PM, Michael Davidsaver <mdavidsaver at gmail.com <mailto:mdavidsaver at gmail.com>> wrote:
>>
>> On 8/3/20 6:07 PM, Johnson, Andrew N. wrote:
>>> No. I get non-zero milli- and microseconds in my time stamps now, but (counting after the decimal point) digits 7 through 9 of a %.9f seconds value are always zero.
>>
>> Ok, then this seems likely to be no worse that Windows.
>> Out of curiosity, have you checked (eg. with epicsTimerTest)
>> to see what the minimum delta actually is?
> 
> In the Github issue yesterday I explained that on my laptop reading the time using the Mach clock_get_time() API takes about 1.6 microseconds and gives nanosecond precision, whereas using clock_gettime() takes only about 58 nanoseconds but gives microsecond precision (as averaged over 100000 readings by epicsTimeTest). Which is better?

I was referring to the smallest non-zero delta in the time
values returned by consecutive calls.  aka. is it really
microsecond precision?

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System