Subject: Re: [boost] [chrono] v0.3.1 Support for wide characters
From: vicente.botet (vicente.botet_at_[hidden])
Date: 2010-01-20 17:52:40
Hi Joel,
----- Original Message -----
From: "joel falcou" <joel.falcou_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Wednesday, January 20, 2010 11:05 PM
Subject: Re: [boost] [chrono] v0.3.1 Support for wide characters
>
> I kinda missed the last shot of comments but I have a question.
> You speak about:
>> * stopwatch_accumulator, capturing cummulated elapsed Clock times.
> Do they use boost::accumulators and if yes, can we give them special
> stats to compute in addition to
> min,max,mean ?
Yes, it uses boost::accumulators so you can give it the Accumulator you want and of course define the associated formatter. I have not included an example on the documentation, but you can have an idea by looking on how stopwatch_accumulator is done and how the default accumulators is given. Here follow an example not yet compiled:
#include <boost/chrono/stopwatches.hpp>
#include <cmath>
using namespace boost::chrono;
using namespace boost::accumulators;
typedef stopwatch_accumulator<process_real_cpu_clock,
accumulator_set<process_real_cpu_clock::rep,
features<
tag::count,
tag::sum,
tag::min,
tag::max,
tag::mean
>
>,
my_stopwatch_accumulator_formatter
>::reporter my_stopwatch_accumulator_reporter;
// where my_stopwatch_accumulator_formatter will follow the same schema that stopwatch_accumulator_formatter.hpp
int f1(long j)
{
static my_stopwatch_accumulator_reporter acc(BOOST_CHRONO_ACCUMULATOR_FUNCTION_FORMAT);
my_stopwatch_accumulator_reporter::scoped_run _(acc);
for ( long i = 0; i < j; ++i )
std::sqrt( 123.456L ); // burn some time
return 0;
}
int main()
{
f1(100000);
f1(200000);
f1(300000);
return 0;
}
> Other questions: is there plan for a cycle counter absed watch using the
> various compiler/os specific stuff like rdtsc et al ?
I'm sorry, but I suspect that I'm not competent in this domain. A clock don't require too much things. Thus for some one with a good knowledge of what is "a cycle counter absed watch using the various compiler/os specific stuff like rdtsc et al" it should be quite easy to implement a clock based on this counting. Here follows an extract from the documentation:
A clock represents a bundle consisting of a native duration, a native time_point, and a function now() to get the current time_point. A clock must meet the requirements in the following Table.
In this table C1 and C2 denote clock types. t1 and t2 are values returned from C1::now() where the call returning t1 happens before the call returning t2 and both of these calls happen before C1::time_point::max().
Table 1. Clock Requirements
expression return type operational semantics
C1::rep An arithmetic type or class emulating an arithmetic type. The representation type of the native duration and time_point.
C1::period ratio The tick period of the clock in seconds.
C1::duration chrono::duration<C1::rep, C1::period> The native duration type of the clock.
C1::time_point chrono::time_point<C1> or chrono::time_point<C2, C1::duration> The native time_point type of the clock. Different clocks are permitted to share a time_point definition if it is valid to compare their time_points by comparing their respective durations. C1 and C2 must refer to the same epoch.
C1::is_monotonic const bool true if t1 <= t2 is always true, else false. Note: A clock that can be adjusted backwards is not monotonic
C1::now() C1::time_point Returns a time_point representing the current point in time.
You could find a better formmating on the documentation.
As you can see, you need just to implement a static function returning this counter. The rest is pure formalism.
Hoping this answer your questions.
Vicente