SimGrid  3.18
Versatile Simulation of Distributed Systems
examples/s4u/exec-ptask/s4u-exec-ptask.cpp
/* Copyright (c) 2017. The SimGrid Team. All rights reserved. */
/* This program is free software; you can redistribute it and/or modify it
* under the terms of the license (GNU LGPL) which comes with this package. */
/* Parallel tasks are convenient abstractions of parallel computational kernels that span over several machines.
* To create a new one, you have to provide several things:
* - a vector of hosts on which the task will execute
* - a vector of values, the amount of computation for each of the hosts (in flops)
* - a matrix of values, the amount of communication between each pair of hosts (in bytes)
*
* Each of these operation will be processed at the same relative speed.
* This means that at some point in time, all sub-executions and all sub-communications will be at 20% of completion.
* Also, they will all complete at the exact same time.
*
* This is obviously a simplistic abstraction, but this is very handful in a large amount of situations.
*
* Please note that you must have the LV07 platform model enabled to use such constructs.
*/
#include <simgrid/s4u.hpp>
#include <xbt/ex.hpp>
#include <xbt/log.h>
XBT_LOG_NEW_DEFAULT_CATEGORY(s4u_energyptask, "Messages specific for this s4u example");
static void runner()
{
/* Retrieve the list of all hosts as an array of hosts */
int hosts_count = sg_host_count();
XBT_INFO("First, build a classical parallel task, with 1 Gflop to execute on each node, "
"and 10MB to exchange between each pair");
double* computation_amounts = new double[hosts_count]();
double* communication_amounts = new double[hosts_count * hosts_count]();
for (int i = 0; i < hosts_count; i++)
computation_amounts[i] = 1e9; // 1 Gflop
for (int i = 0; i < hosts_count; i++)
for (int j = i + 1; j < hosts_count; j++)
communication_amounts[i * hosts_count + j] = 1e7; // 10 MB
simgrid::s4u::this_actor::parallel_execute(hosts_count, hosts, computation_amounts, communication_amounts);
XBT_INFO("We can do the same with a timeout of one second enabled.");
computation_amounts = new double[hosts_count]();
communication_amounts = new double[hosts_count * hosts_count]();
for (int i = 0; i < hosts_count; i++)
computation_amounts[i] = 1e9; // 1 Gflop
for (int i = 0; i < hosts_count; i++)
for (int j = i + 1; j < hosts_count; j++)
communication_amounts[i * hosts_count + j] = 1e7; // 10 MB
try {
simgrid::s4u::this_actor::parallel_execute(hosts_count, hosts, computation_amounts, communication_amounts,
1.0 /* timeout (in seconds)*/);
XBT_WARN("Woops, this did not timeout as expected... Please report that bug.");
} catch (xbt_ex& e) {
/* Do nothing this exception on timeout was expected */
XBT_DEBUG("Caught expected exception: %s", e.what());
}
XBT_INFO("Then, build a parallel task involving only computations and no communication (1 Gflop per node)");
computation_amounts = new double[hosts_count]();
for (int i = 0; i < hosts_count; i++)
computation_amounts[i] = 1e9; // 1 Gflop
simgrid::s4u::this_actor::parallel_execute(hosts_count, hosts, computation_amounts, nullptr /* no comm */);
XBT_INFO("Then, build a parallel task with no computation nor communication (synchro only)");
computation_amounts = new double[hosts_count]();
communication_amounts = new double[hosts_count * hosts_count]();
simgrid::s4u::this_actor::parallel_execute(hosts_count, hosts, computation_amounts, communication_amounts);
XBT_INFO("Finally, trick the ptask to do a 'remote execution', on host %s", hosts[1]->getCname());
computation_amounts = new double[1]{1e9};
simgrid::s4u::Host* remote[] = {hosts[1]};
simgrid::s4u::this_actor::parallel_execute(1, remote, computation_amounts, nullptr);
XBT_INFO("Goodbye now!");
std::free(hosts);
}
int main(int argc, char* argv[])
{
simgrid::s4u::Engine e(&argc, argv);
xbt_assert(argc <= 3, "1Usage: %s <platform file> [--energy]", argv[0]);
xbt_assert(argc >= 2, "2Usage: %s <platform file> [--energy]", argv[0]);
if (argc == 3 && argv[2][2] == 'e')
e.loadPlatform(argv[1]);
/* Pick a process, no matter which, from the platform file */
e.run();
XBT_INFO("Simulation done.");
return 0;
}