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profiling

This is a very simple example of the use of events and monitors to make profilers for an application. It's easy to modify to make it do much more. For instance, most Prolog compilers give you access to data concerning space usage (stacks, heap, etc).

The example defines three objects:

[109, 101, 115, 115, 97, 103, 101, 95, 99, 111, 117, 110, 116, 101, 114]

using events, this object allows us to count the messages sent to spied objects

[115, 116, 111, 112, 95, 119, 97, 116, 99, 104]

using events, this object simply prints the CPU time before and after a message sent to a spied object

[116, 105, 109, 101, 114]

this object implements a method that sends a message to an object a specified number of times, returning the average execution time

Print Logtalk, Prolog backend, and kernel versions (if running as a notebook):

%versions

Start by loading the example and the required library files:

logtalk_load(profiling(loader)).

Turn event support on for messages sent at the command-line (i.e., for messages sent from the pseudo-object user):

set_logtalk_flag(events, allow).

<!-- true. -->

message_counter example:

Choose an object to spy:

message_counter::set_spy_point(_, list, _, _).

<!-- true. -->

Activate the monitor:

message_counter::activate_monitor.

<!-- true. -->

Send some messages to the spied object; get all the answers for ancestor/1:

list::empty([]).

<!-- true. -->

list::member(X, [1, 2, 3]).

<!-- X = 1 ? ; X = 2 ? ; X = 3 ? ; false. -->

Print a report of the data collected by the monitor:

message_counter::report.

<!-- list total of calls: 2 total of exits: 4

empty/1 calls: 1 exits: 1

member/2 calls: 1 exits: 3

true. -->

Stop and reset the message counter monitor:

message_counter::stop.

<!-- true. -->

stop_watch example

Choose a pair object/message to spy:

stop_watch::set_spy_point(_, list, length(_, _), _).

<!-- true. -->

Activate the monitor:

stop_watch::activate_monitor.

<!-- true. -->

Send a message to the spied object:

list::length([1, 2, 3], Length).

<!-- list <-- length([1,2,3],_277) from user STARTING at 755.69000005 seconds list <-- length([1,2,3],3) from user ENDING at 755.69000235 seconds

Length = 3. -->

Clean up:

stop_watch::reset_monitor.

<!-- true. -->

timer example

Try a message 1000 times and return the average time:

timer::timer(list::length([1, 2, 3], _), 1000, Time).

<!-- Time = 0.00003 -->

Turn event support off:

set_logtalk_flag(events, deny).

<!-- true. -->