Re: [Boost-users] [chrono] float-based milliseconds?

Subject: Re: [Boost-users] [chrono] float-based milliseconds?
From: Michael Powell (mwpowellhtx_at_[hidden])
Date: 2013-08-30 19:50:18

I should clarify, I suspect that it is being configure as doubles, but
I could be mistaken. Instead I need to find out whether it's possible
to set it up as single-precision float. Or does the fact that the
high-resolution nature of Chrono steady-clock "long long int" preclude
that?

On Fri, Aug 30, 2013 at 6:34 PM, Brian Budge <brian.budge_at_[hidden]> wrote:
> On Fri, Aug 30, 2013 at 4:26 PM, Michael Powell <mwpowellhtx_at_[hidden]> wrote:
>> Hello,
>>
>> Or any of the chrono-steady-clock-based time units...
>>
>> I am noticing some what appear to be rounding errors outputting
>> resulting millisecond values using the boost::chrono::milliseconds(x).
>>
>> It's a design-decision, most if not all of our floating-point values
>> are single-precision-float, don't need to be double-precision-float.
>>
>> When we output the milliseconds(x).count() values, however, what I am
>> finding is that the values are sometimes inaccurate, the same value in
>> 3.0, for instance, output as 2.99995, stuff like this.
>>
>> Is there a way to tell milliseconds what precision floating point it
>> is? float or double?
>>
>> We are targeting ARM, BTW, without hardware floating point support,
>> which is the main reason, I'd like to keep things single-precision
>> float, if at all possible.
>>
>
> Hi Michael -
>
> I don't know the answer to this question (can chrono be configured to
> use doubles); however, I thought it might be useful to point out that
> when you're talking about 5 decimal digits of precision at
> milliseconds, you're only going to be off by a couple of tens of
> nanoseconds, which is likely less than the precision of any timer on
> the system.
>
>   Brian
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