1 /* Copyright (c) 2017-2022. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 #include <simgrid/s4u.hpp>
8 /* This example shows how to use sg4::Engine::get_filtered_hosts() to retrieve
9 * all hosts that match a given criteria. This criteria can be specified either with:
10 * - an inlined callback
11 * - a boolean function, such as filter_speed_more_than_50Mf() below
12 * - a functor (= function object), that can either be stateless such as filter::SingleCore below, or that can save
13 * state such as filter::FrequencyChanged below
15 * This file provides examples for each of these categories. You should implement your own filters in your code.
18 XBT_LOG_NEW_DEFAULT_CATEGORY(s4u_engine_filtering, "Messages specific for this s4u example");
19 namespace sg4 = simgrid::s4u;
22 /* First example of thing that we can use as a filtering criteria: a simple boolean function */
23 static bool filter_speed_more_than_50Mf(const sg4::Host* host)
25 return host->get_speed() > 50E6;
28 /* Second kind of thing that we can use as a filtering criteria: a functor (=function object).
29 * This one is a bit stupid: it's a lot of boilerplate over a dummy boolean function.
33 bool operator()(const sg4::Host* host) const { return host->get_core_count() == 1; }
36 /* This functor is a bit more complex, as it saves the current state when created.
37 * Then, it allows one to easily retrieve the hosts which frequency changed since the functor creation.
39 class FrequencyChanged {
40 std::map<sg4::Host*, unsigned long> host_list;
43 explicit FrequencyChanged(const sg4::Engine& e)
45 std::vector<sg4::Host*> list = e.get_all_hosts();
46 for (auto& host : list) {
47 host_list.insert({host, host->get_pstate()});
51 bool operator()(sg4::Host* host) { return host->get_pstate() != host_list.at(host); }
53 unsigned long get_old_speed_state(sg4::Host* host) { return host_list.at(host); }
56 int main(int argc, char* argv[])
58 sg4::Engine e(&argc, argv);
59 e.load_platform(argv[1]);
61 /* Use a lambda function to filter hosts: We only want multicore hosts */
62 XBT_INFO("Hosts currently registered with this engine: %zu", e.get_host_count());
63 std::vector<sg4::Host*> list = e.get_filtered_hosts([](const sg4::Host* host) { return host->get_core_count() > 1; });
65 for (auto& host : list)
66 XBT_INFO("The following hosts have more than one core: %s", host->get_cname());
68 xbt_assert(list.size() == 1);
70 /* Use a function object (functor) without memory */
71 list = e.get_filtered_hosts(filter::SingleCore());
73 for (auto& host : list)
74 XBT_INFO("The following hosts are SingleCore: %s", host->get_cname());
76 /* Use a function object that uses memory to filter */
77 XBT_INFO("A simple example: Let's retrieve all hosts that changed their frequency");
78 filter::FrequencyChanged filter(e);
79 e.host_by_name("MyHost2")->set_pstate(2);
80 list = e.get_filtered_hosts(filter);
82 for (auto& host : list)
83 XBT_INFO("The following hosts changed their frequency: %s (from %.1ff to %.1ff)", host->get_cname(),
84 host->get_pstate_speed(filter.get_old_speed_state(host)), host->get_speed());
86 /* You can also just use any regular function (namespaced on need) to filter */
87 list = e.get_filtered_hosts(filter::filter_speed_more_than_50Mf);
89 for (auto& host : list)
90 XBT_INFO("The following hosts have a frequency > 50Mf: %s", host->get_cname());