/*
   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 * Authors:
 *      Benjamin Bouvier <benjamin.bouvier@gmail.com>
 */

/**
 * @file t-mpi-distrib-exp.cpp
 * @brief File for parallel experimentations.
 *
 * When using parallel evaluation, the individuals to evaluate are sent by packets (group),
 * so as to avoid that communication time be more important than worker's execution time.
 * However, the ideal size of packet depends on the problem and the time needed to carry out
 * the atomic operation on each individual. This experiment tries to find a relation between
 * the total number of elements to process (size), the execution time and the size of packet.
 * This could lead to an heuristic allowing to optimize the size of packet according to the
 * processing times.
 */
# include <unistd.h> // usleep

# include <iostream>
# include <iomanip>
# include <string>
# include <vector>

# include <eo>

# include <mpi/eoParallelApply.h>
# include "t-mpi-common.h"

using namespace eo::mpi;

// Serializable int
typedef SerializableBase<int> type;

/*
 * The task is the following: the worker receives a number of milliseconds to wait, which
 * simulates the process of one individual. This way, the sequences of processing times are
 * generated only by the master and are more easily reproductible.
 */
struct Wait : public eoUF< type &, void >
{
    Wait( bool print ) : _print( print )
    {
        // empty
    }

    void operator()( type & milliseconds )
    {
        if( _print )
            std::cout << "Sleeping for " << milliseconds << "ms..." << std::endl;
        // usleep takes an input in microseconds
        usleep( milliseconds * 1000 );
    }

    private:
    bool _print;
};

/**
 * @brief Represents a distribution of processing times.
 */
class Distribution : public std::vector< type >
{
    public:

    /**
     * @brief Really fills the vector with the distribution values.
     */
    void fill( unsigned size )
    {
        for( unsigned i = 0; i < size; ++i )
        {
            int next = next_element();
            if( next < 0 ) next = 0;
            push_back( next );
        }
    }

    /**
     * @brief Returns the next element of the distribution to put in the
     * vector.
     *
     * @returns Number of milliseconds to wait. Can be negative ; in this case,
     * the number will be truncated to 0ms.
     */
    virtual int next_element() = 0;

    /**
     * @brief Creates params and retrieves values from parser
     *
     * Parser's params should take milliseconds as inputs.
     */
    virtual void make_parser( eoParser & parser ) = 0;

    /**
     * @brief Returns true if this distribution has been activated by the
     * command line.
     *
     * Used by the main program so as to check if at least one distribution has been
     * activated.
     */
    bool isActive() { return _active; }

    protected:

    bool _active;
};

/**
 * @brief Uniform distribution.
 *
 * This is an uniform distribution, defined by a minimum value and a maximum value.
 * In the uniform distribution, every number from min to max has the same probability
 * to appear.
 *
 * The 3 parameters activable from a parser are the following:
 * - uniform=1 : if we want to use the uniform distribution
 * - uniform-min=x : use x milliseconds as the minimum value of waiting time.
 * - uniform-max=y : use y milliseconds as the maximum value of waiting time.
 * Ensure that x < y, or the results are unpredictable.
 */
class UniformDistribution : public Distribution
{
    public:

    UniformDistribution() : _rng(0)
    {
        // empty
    }

    void make_parser( eoParser & parser )
    {
        _active = parser.createParam( false, "uniform", "Uniform distribution", '\0', "Uniform").value();
        _min = parser.createParam( 0.0, "uniform-min", "Minimum for uniform distribution, in ms.", '\0', "Uniform").value();
        _max = parser.createParam( 1.0, "uniform-max", "Maximum for uniform distribution, in ms.", '\0', "Uniform").value();
    }

    int next_element()
    {
        return std::floor( _rng.uniform( _min, _max ) );
    }

    protected:

    eoRng _rng;

    double _min;
    double _max;

} uniformDistribution;

/**
 * @brief Normal (gaussian) distribution of times.
 *
 * A normal distribution is defined by a mean and a standard deviation.
 * The 3 parameters activable from the parser are the following:
 * - normal=1: activates the gaussian distribution.
 * - normal-mean=50: use 50ms as the mean of the distribution.
 * - normal-stddev=10: use 10ms as the standard deviation of the distribution.
 */
class NormalDistribution : public Distribution
{
    public:

    NormalDistribution() : _rng( 0 )
    {
        // empty
    }

    void make_parser( eoParser & parser )
    {
        _active = parser.createParam( false, "normal", "Normal distribution", '\0', "Normal").value();
        _mean = parser.createParam( 0.0, "normal-mean", "Mean for the normal distribution (0 by default), in ms.", '\0', "Normal").value();
        _stddev = parser.createParam( 1.0, "normal-stddev", "Standard deviation for the normal distribution (1ms by default), 0 isn't acceptable.", '\0', "Normal").value();
    }

    int next_element()
    {
        return std::floor( _rng.normal( _mean, _stddev ) );
    }

    protected:

    eoRng _rng;
    double _mean;
    double _stddev;
} normalDistribution;

/**
 * @brief Exponential distribution.
 *
 * This distribution belongs to the category of the decreasing power laws and are affected by long trails
 * phenomenons.
 * An exponential distribution is only defined by its mean.
 *
 * The 2 parameters activable from the parser are the following:
 * - exponential=1: to activate the exponential distribution.
 * - exponential-mean=50: indicates that the mean must be 50ms.
 */
class ExponentialDistribution : public Distribution
{
    public:

    ExponentialDistribution() : _rng( 0 )
    {
        // empty
    }

    void make_parser( eoParser & parser )
    {
        _active = parser.createParam( false, "exponential", "Exponential distribution", '\0', "Exponential").value();
        _mean = parser.createParam( 0.0, "exponential-mean", "Mean for the exponential distribution (0 by default), in ms.", '\0', "Exponential").value();
    }

    int next_element()
    {
        return std::floor( _rng.negexp( _mean ) );
    }

    protected:

    eoRng _rng;
    double _mean;

} exponentialDistribution;

int main( int argc, char** argv )
{
    Node::init( argc, argv );
    mpi::communicator& comm = eo::mpi::Node::comm();
    eoParser parser( argc, argv );

    // forces the statistics to be retrieved
    parser.setORcreateParam( true, "parallelize-do-measure", "Do some measures during execution" );

    // General parameters for the experimentation
    unsigned size = parser.createParam( 10U, "size", "Number of elements to distribute.", 's', "Distribution").value();
    unsigned packet_size = parser.createParam( 1U, "packet-size", "Number of elements to distribute at each time for a single worker.", 'p', "Parallelization").value();
    bool worker_print_waiting_time = parser.createParam( false, "print-waiting-time", "Do the workers need to print the time they wait?", '\0', "Parallelization").value();

    std::vector<Distribution*> distribs;
    distribs.push_back( &uniformDistribution );
    distribs.push_back( &normalDistribution );
    distribs.push_back( &exponentialDistribution );

    // for each available distribution, check if activated.
    // If no distribution is activated, show an error message
    // If two distributions or more are activated, show an error message
    // Otherwise, use the activated distribution as distrib
    bool isChosenDistrib = false;
    Distribution* pdistrib = 0;
    for( int i = 0, s = distribs.size(); i < s; ++i )
    {
        distribs[i]->make_parser( parser );
        if( distribs[i]->isActive() )
        {
            if( isChosenDistrib )
            {
                throw std::runtime_error("Only one distribution can be chosen during a launch!");
            } else
            {
                isChosenDistrib = true;
                pdistrib = distribs[i];
            }
        }
    }

    make_parallel( parser );
    make_help( parser );

    if( !isChosenDistrib )
    {
        throw std::runtime_error("No distribution chosen. One distribution should be chosen.");
    }

    // Fill distribution
    Distribution& distrib = *pdistrib;
    distrib.fill( size );

    Wait wait( worker_print_waiting_time );
    ParallelApplyStore< type > store( wait, DEFAULT_MASTER, packet_size );
    store.data( distrib );
    DynamicAssignmentAlgorithm scheduling;
    ParallelApply< type > job( scheduling, DEFAULT_MASTER, store );

    job.run();
    if( job.isMaster() )
    {
        EmptyJob( scheduling, DEFAULT_MASTER ); // to terminate parallel apply
        // Receive statistics
        typedef std::map< std::string, eoTimerStat::Stat > typeStats;
        std::cout << std::fixed << std::setprecision( 5 );
        for( int i = 1, s = comm.size(); i < s; ++i )
        {
            eoTimerStat timerStat;
            comm.recv( i, eo::mpi::Channel::Commands, timerStat );
            typeStats stats = timerStat.stats();
            for( typeStats::iterator it = stats.begin(),
                    end = stats.end();
                 it != end;
                 ++it )
            {
                std::cout << "Worker " << i << ": Wallclock time of " << it->first << std::endl;
                for( int j = 0, t = it->second.wtime.size(); j < t; ++j )
                {
                    std::cout << it->second.wtime[j] << " ";
                }
                std::cout << std::endl;
            }
            std::cout << std::endl;
        }
    } else
    {
        // Send statistics
        comm.send( DEFAULT_MASTER, eo::mpi::Channel::Commands, eo::mpi::timerStat );
    }

    return 0;
}