AMPL solver times

[adit...@gmail.com]

Hello Group Members,

I am using AMPL / BARON for one of my class project.

For my problem, I need to separately report the time AMPL took to load the model, and the time solver took to solve it.

I went through timing parameters listed in 'Table A-14: Built-in timing parameters' in AMPL manual (https://ampl.com/BOOK/CHAPTERS/24-refman.pdf#page=44) to understand this.

However, it is still not clear to me that which 'time options' I need to use. Kindly help me with the same.

Thanks,

Aditya

 

[AMPL Google Group]

The time taken by the most recent call to a solver can be measured in either of two ways:

• _solve_time = "CPU time" = the processor time used by the solver, not counting time taken by other processes that are also running
• _solve_elapsed_time = "wall-clock time" = the time you had to wait between invoking "solve" and getting a solution back

For single-threaded solves (running on one processor core), _solve_time tends to be more accurate. For multi-threaded solves (running on more than one core in parallel), _solve_elapsed_time should be used. BARON runs single-threaded by default but can be made to run multi-threaded; search for "thread" in the BARON manual to learn more.

Also if you set outlev=1 in your baron_options string then BARON will display the CPU and wall-clock times in the summary at the end of its listing. These times do not include the overhead of the AMPL-BARON interface, and so they will be a little less than the times reported in _solve_time and _solve_elapsed_time.

AMPL runs single-threaded, so for the time spent in AMPL you should use _ampl_time. This is the time since the AMPL session began, so to find the time spent in AMPL for generating a problem file and processing results, you need to measure _ampl_time before and after a solve, and record the difference. For example, you could define "param ampl_start_time;" and then proceed like this:

let ampl_start_time := _ampl_time;
solve;
display _ampl_time - ampl_start_time;

In fact you can use "_ampl_time - ampl_start_time" in any AMPL statement where a number is appropriate.

--
Robert Fourer
am...@googlegroups.com

{#HS:1622908814-106184#}

[adit...@gmail.com]

Thanks Robert for your useful answer. It is very clear.

I think for me the best option is outlev = 1 because I am only interested in the time BARON takes to solve the model, and not in the time AMPL takes to load the model in BARON.

Regards,

Aditya