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Implement a simulation clock type #858

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program-- opened this issue Jul 22, 2024 · 2 comments · May be fixed by #881
Open

Implement a simulation clock type #858

program-- opened this issue Jul 22, 2024 · 2 comments · May be fixed by #881
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enhancement New feature or request

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@program--
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program-- commented Jul 22, 2024 •
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Currently, across Data Providers and BMI instances, we're primarily using C time constructs.

Example

ngen/include/forcing/DataProvider.hpp

Lines 47 to 54 in 9fc3182

virtual long get_data_start_time() const = 0;
/** Return the last valid time for which data from the requested variable can be requested */
virtual long get_data_stop_time() const = 0;
/** Return the stride in the time dimension */
virtual long record_duration() const = 0;

ngen/include/simulation_time/Simulation_Time.hpp

Lines 171 to 173 in 9fc3182

time_t start_date_time_epoch;
time_t end_date_time_epoch;
time_t current_date_time_epoch;

However, in some recent changes, we've started using std::chrono types.

Example

ngen/include/forcing/ForcingsEngineDataProvider.hpp

Lines 208 to 214 in 9fc3182

clock_type::time_point time_begin_{};
//! Calendar time for simulation end
clock_type::time_point time_end_{};
//! Duration of a single simulation tick
clock_type::duration time_step_{};

One of the current issues with std::chrono clock types is that they either represent Unix time or relative time (though not clearly), and we have a use-case for representing both. A potential solution for this is to define our own clock type1, simulation_clock, as discussed here.

A benefit is that this would allow us to use std::chrono types while maintaining control of the simulation ticks however we see fit.

Footnotes

  1. https://en.cppreference.com/w/cpp/named_req/Clock ↩
@program-- program-- added the enhancement New feature or request label Jul 22, 2024
@program-- program-- mentioned this issue Jul 22, 2024
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@program-- program-- mentioned this issue Aug 8, 2024
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@program--
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An attempt at fleshing out an interface similar to the discussed one in the above linked comment. However, unlike conventional chrono clocks, this implementation is a controlled clock, where simulation_clock::now() doesn't change unless simulation_clock::tick(...) is called.

https://github.com/program--/ngen/blob/8c21f8e3540942468b8126a01ce99da33c61e7fb/include/simulation_time/simulation_clock.hpp#L9-L123

@PhilMiller
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The implementation you've drafted looks pretty good to me. May as well post it in a PR, and we can potentially start using it in the Forcings Engine and Coastal Formulation code that we're writing fresh.

@program-- program-- linked a pull request Sep 11, 2024 that will close this issue
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Implement simulation_clock type program--/ngen
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@PhilMiller @program--