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Diffstat (limited to 'ml/dlib/examples/bsp_ex.cpp')
| -rw-r--r-- | ml/dlib/examples/bsp_ex.cpp | 282 |
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diff --git a/ml/dlib/examples/bsp_ex.cpp b/ml/dlib/examples/bsp_ex.cpp deleted file mode 100644 index 7dffa68d6..000000000 --- a/ml/dlib/examples/bsp_ex.cpp +++ /dev/null @@ -1,282 +0,0 @@ -// The contents of this file are in the public domain. See LICENSE_FOR_EXAMPLE_PROGRAMS.txt -/* - - This is an example illustrating the use of the Bulk Synchronous Parallel (BSP) - processing tools from the dlib C++ Library. These tools allow you to easily setup a - number of processes running on different computers which cooperate to compute some - result. - - In this example, we will use the BSP tools to find the minimizer of a simple function. - In particular, we will setup a nested grid search where different parts of the grid are - searched in parallel by different processes. - - - To run this program you should do the following (supposing you want to use three BSP - nodes to do the grid search and, to make things easy, you will run them all on your - current computer): - - 1. Open three command windows and navigate each to the folder containing the - compiled bsp_ex.cpp program. Let's call these window 1, window 2, and window 3. - - 2. In window 1 execute this command: - ./bsp_ex -l12345 - This will start a listening BSP node that listens on port 12345. The BSP node - won't do anything until we tell all the nodes to start running in step 4 below. - - 3. In window 2 execute this command: - ./bsp_ex -l12346 - This starts another listening BSP node. Note that since we are running this - example all on one computer you need to use different listening port numbers - for each listening node. - - 4. In window 3 execute this command: - ./bsp_ex localhost:12345 localhost:12346 - This will start a BSP node that connects to the others and gets them all running. - Additionally, as you will see when we go over the code below, it will also print - the final output of the BSP process, which is the minimizer of our test function. - Once it terminates, all the other BSP nodes will also automatically terminate. -*/ - - - - - -#include <dlib/cmd_line_parser.h> -#include <dlib/bsp.h> -#include <dlib/matrix.h> - -#include <iostream> - -using namespace std; -using namespace dlib; - -// ---------------------------------------------------------------------------------------- - -// These are the functions executed by the BSP nodes. They are defined below. -void bsp_job_node_0 (bsp_context& bsp, double& min_value, double& optimal_x); -void bsp_job_other_nodes (bsp_context& bsp, long grid_resolution); - -// ---------------------------------------------------------------------------------------- - -int main(int argc, char** argv) -{ - try - { - // Use the dlib command_line_parser to parse the command line. See the - // compress_stream_ex.cpp example program for an introduction to the command line - // parser. - command_line_parser parser; - parser.add_option("h","Display this help message."); - parser.add_option("l","Run as a listening BSP node.",1); - parser.parse(argc, argv); - parser.check_option_arg_range("l", 1, 65535); - - - // Print a help message if the user gives -h on the command line. - if (parser.option("h")) - { - // display all the command line options - cout << "Usage: bsp_ex (-l port | <list of hosts>)\n"; - parser.print_options(); - return 0; - } - - - // If the command line contained -l - if (parser.option("l")) - { - // Get the argument to -l - const unsigned short listening_port = get_option(parser, "l", 0); - cout << "Listening on port " << listening_port << endl; - - const long grid_resolution = 100; - - // bsp_listen() starts a listening BSP job. This means that it will wait until - // someone calls bsp_connect() and connects to it before it starts running. - // However, once it starts it will call bsp_job_other_nodes() which will then - // do all the real work. - // - // The first argument is the port to listen on. The second argument is the - // function which it should run to do all the work. The other arguments are - // optional and allow you to pass values into the bsp_job_other_nodes() - // routine. In this case, we are passing the grid_resolution to - // bsp_job_other_nodes(). - bsp_listen(listening_port, bsp_job_other_nodes, grid_resolution); - } - else - { - if (parser.number_of_arguments() == 0) - { - cout << "You must give some listening BSP nodes as arguments to this program!" << endl; - return 0; - } - - // Take the hostname:port strings from the command line and put them into the - // vector of hosts. - std::vector<network_address> hosts; - for (unsigned long i = 0; i < parser.number_of_arguments(); ++i) - hosts.push_back(parser[i]); - - double min_value, optimal_x; - - // Calling bsp_connect() does two things. First, it tells all the BSP jobs - // listed in the hosts vector to start running. Second, it starts a locally - // running BSP job that executes bsp_job_node_0() and passes it any arguments - // listed after bsp_job_node_0. So in this case it passes it the 3rd and 4th - // arguments. - // - // Note also that we use dlib::ref() which causes these arguments to be passed - // by reference. This means that bsp_job_node_0() will be able to modify them - // and we will see the results here in main() after bsp_connect() terminates. - bsp_connect(hosts, bsp_job_node_0, dlib::ref(min_value), dlib::ref(optimal_x)); - - // bsp_connect() and bsp_listen() block until all the BSP nodes have terminated. - // Therefore, we won't get to this part of the code until the BSP processing - // has finished. But once we do we can print the results like so: - cout << "optimal_x: "<< optimal_x << endl; - cout << "min_value: "<< min_value << endl; - } - - } - catch (std::exception& e) - { - cout << "error in main(): " << e.what() << endl; - } -} - -// ---------------------------------------------------------------------------------------- - -/* - We are going to use the BSP tools to find the minimum of f(x). Note that - it's minimizer is at x == 2.0. -*/ -double f (double x) -{ - return std::pow(x-2.0, 2.0); -} - -// ---------------------------------------------------------------------------------------- - -void bsp_job_node_0 (bsp_context& bsp, double& min_value, double& optimal_x) -{ - // This function is called by bsp_connect(). In general, any BSP node can do anything - // you want. However, in this example we use this node as a kind of controller for the - // other nodes. In particular, since we are doing a nested grid search, this node's - // job will be to collect results from other nodes and then decide which part of the - // number line subsequent iterations should focus on. - // - // Also, each BSP node has a node ID number. You can determine it by calling - // bsp.node_id(). However, the node spawned by a call to bsp_connect() always has a - // node ID of 0 (hence the name of this function). Additionally, all functions - // executing a BSP task always take a bsp_context as their first argument. This object - // is the interface that allows BSP jobs to communicate with each other. - - - // Now let's get down to work. Recall that we are trying to find the x value that - // minimizes the f(x) defined above. The grid search will start out by considering the - // range [-1e100, 1e100] on the number line. It will progressively narrow this window - // until it has located the minimizer of f(x) to within 1e-15 of its true value. - double left = -1e100; - double right = 1e100; - - min_value = std::numeric_limits<double>::infinity(); - double interval_width = std::abs(right-left); - - // keep going until the window is smaller than 1e-15. - while (right-left > 1e-15) - { - // At the start of each loop, we broadcast the current window to all the other BSP - // nodes. They will each search a separate part of the window and then report back - // the smallest values they found in their respective sub-windows. - // - // Also, you can send/broadcast/receive anything that has global serialize() and - // deserialize() routines defined for it. Dlib comes with serialization functions - // for a lot of types by default, so we don't have to define anything for this - // example program. However, if you want to send an object you defined then you - // will need to write your own serialization functions. See the documentation for - // dlib's serialize() routine or the bridge_ex.cpp example program for an example. - bsp.broadcast(left); - bsp.broadcast(right); - - // Receive the smallest values found from the other BSP nodes. - for (unsigned int k = 1; k < bsp.number_of_nodes(); ++k) - { - // The other nodes will send std::pairs of x/f(x) values. So that is what we - // receive. - std::pair<double,double> val; - bsp.receive(val); - // save the smallest result. - if (val.second < min_value) - { - min_value = val.second; - optimal_x = val.first; - } - } - - // Now narrow the search window by half. - interval_width *= 0.5; - left = optimal_x - interval_width/2; - right = optimal_x + interval_width/2; - } -} - -// ---------------------------------------------------------------------------------------- - -void bsp_job_other_nodes (bsp_context& bsp, long grid_resolution) -{ - // This is the BSP job called by bsp_listen(). In these jobs we will receive window - // ranges from the controller node, search our sub-window, and then report back the - // location of the best x value we found. - - double left, right; - - // The try_receive() function will either return true with the next message or return - // false if there aren't any more messages in flight between nodes and all other BSP - // nodes are blocked on calls to receive or have terminated. That is, try_receive() - // only returns false if waiting for a message would result in all the BSP nodes - // waiting forever. - // - // Therefore, try_receive() serves both as a message receiving tool as well as an - // implicit form of barrier synchronization. In this case, we use it to know when to - // terminate. That is, we know it is time to terminate if all the messages between - // nodes have been received and all nodes are inactive due to either termination or - // being blocked on a receive call. This will happen once the controller node above - // terminates since it will result in all the other nodes inevitably becoming blocked - // on this try_receive() line with no messages to process. - while (bsp.try_receive(left)) - { - bsp.receive(right); - - // Compute a sub-window range for us to search. We use our node's ID value and the - // total number of nodes to select a subset of the [left, right] window. We will - // store the grid points from our sub-window in values_to_check. - const double l = (bsp.node_id()-1)/(bsp.number_of_nodes()-1.0); - const double r = bsp.node_id() /(bsp.number_of_nodes()-1.0); - const double width = right-left; - // Select grid_resolution number of points which are linearly spaced throughout our - // sub-window. - const matrix<double> values_to_check = linspace(left+l*width, left+r*width, grid_resolution); - - // Search all the points in values_to_check and figure out which one gives the - // minimum value of f(). - double best_x = 0; - double best_val = std::numeric_limits<double>::infinity(); - for (long j = 0; j < values_to_check.size(); ++j) - { - double temp = f(values_to_check(j)); - if (temp < best_val) - { - best_val = temp; - best_x = values_to_check(j); - } - } - - // Report back the identity of the best point we found in our sub-window. Note - // that the second argument to send(), the 0, is the node ID to send to. In this - // case we send our results back to the controller node. - bsp.send(make_pair(best_x, best_val), 0); - } -} - -// ---------------------------------------------------------------------------------------- - |