utils_parall.cpp

#include <iostream>
#include <sstream>
#include <mpi.h>

#include "utils_parall.h"
#include "parall_constants.h"
#include "tensormatrix.h"

/*******************************************************************************
 *                         Utilities for parallelism                           *
 *******************************************************************************/

std::string linearize_expression( gi::ex expr ){
    std::ostringstream oss;
    oss << expr;
    return oss.str();
}

gi::ex de_linearize_expression( std::string s, gi::lst symbols ){
    return gi::ex( s, symbols );
}

parameters_t::parameters_t( unsigned int a4,  unsigned int a2, unsigned int a1 ){
    this->a4 = a4;
    this->a2 = a2;
    this->a1 = a1;
}

parameters_2_1_t::parameters_2_1_t( unsigned int a4, unsigned int a2 ){
    this->a4 = a4;
    this->a2 = a2;
}

parameters_2_2_t::parameters_2_2_t( unsigned int a4, unsigned int a2 ){
    this->a6 = a6;
    this->a1 = a1;
}

void create_parameters_datatye(){
    MPI_Type_contiguous( 3, MPI_UNSIGNED, &DT_PARAMETERS );
    MPI_Type_commit( &DT_PARAMETERS );
}

void create_parameters_datatye_2_1(){
    MPI_Type_contiguous( 2, MPI_UNSIGNED, &DT_PARAMETERS_2_1 );
    MPI_Type_commit( &DT_PARAMETERS_2_1 );
}

void create_parameters_datatye_2(){
    MPI_Type_contiguous( 2, MPI_UNSIGNED, &DT_PARAMETERS_2_2 );
    MPI_Type_commit( &DT_PARAMETERS_2_2 );
}

void free_parameters_dt( ){
    MPI_Type_free( &DT_PARAMETERS );
}

void free_parameters_2_1_dt( ){
    MPI_Type_free( &DT_PARAMETERS_2_1 );
}

void free_parameters_2_2_dt( ){
    MPI_Type_free( &DT_PARAMETERS_2_2 );
}

gi::ex add_expressions( std::vector<std::string> expressions, gi::lst symbols ) {
    gi::ex Tens = 0;
    for( auto s: expressions  ) {
        gi::ex received = de_linearize_expression( s, symbols );
        Tens += received;
    }
    return Tens;
}

/* M -> W: Send the end signal */

void send_end( int peer, MPI_Comm comm ) {
    parameters_t para;
    MPI_Send( &para, 1, DT_PARAMETERS, peer, TAG_END, comm );
}

void send_end_batch( int peer, MPI_Comm comm ) {
    parameters_t para;
    MPI_Send( &para, 1, DT_PARAMETERS_2_1, peer, TAG_END_BATCH, comm );
}

/* M -> W: Send some work: just a parameter set */

void send_work( std::vector<parameters_t>& input, int peer, MPI_Comm comm ){
    parameters_t para = input.back();
    input.pop_back();
    MPI_Send( &para, 1, DT_PARAMETERS, peer, TAG_WORK, comm );
}

void send_work( std::vector<parameters_2_1_t>& input, int peer, MPI_Comm comm ){
    parameters_2_1_t para = input.back();
    input.pop_back();
    MPI_Send( &para, 1, DT_PARAMETERS_2_1, peer, TAG_WORK, comm );
}

/* M -> W: Send a set of expressions to be added */

void send_expressions_to_add( std::vector<std::string>& results, int peer ) {

    /* Fill a bogus parameter object */
    int nb = results.size();
    int i;
    parameters_t p( nb, 0, 0 );
    char* expr;

    MPI_Send( &p, 1, DT_PARAMETERS, peer, TAG_ADD, MPI_COMM_WORLD );
    
    /* Send the length of each string */
    unsigned int* lengths = (unsigned int*) malloc( nb*sizeof( unsigned int ) );
    for( i = 0 ; i < nb ; i++ ) {
        lengths[i] = results[i].length();
    }
    MPI_Send( lengths, nb, MPI_INT, peer, TAG_ADD, MPI_COMM_WORLD );

    /* Send the strings (should be nicely pipelined) */
    for( i = 0 ; i < nb ; i++ ) {
        expr = const_cast<char*>( results[i].c_str() );
        MPI_Send( expr, results[i].length(), MPI_CHAR, peer, TAG_ADD, MPI_COMM_WORLD );
    }
    
    results.erase( results.begin(), results.end() );
   
    free( lengths );
}

/* M -> W: Send either a set of expressions to add, or the end signal */

void send_add_or_end_addslave(  std::vector<std::string>& results, int peer, int* running ){
    
    /* Do I have a lot of results to be treated in the result queue? */

    if( results.size() > maxresult ) {
        /* if the result queue is too big, send it */
        send_expressions_to_add( results, peer );
    } else {
        send_end( peer );
        (*running)--;
    }
}

/* M -> W: Send work: either a set of expressions to add, or a parameter set */

void send_work_addslave(  std::vector<parameters_t>& input, std::vector<std::string>& results, int peer ) {

    if( results.size() > maxresult ) {
        /* if the result queue is too big, send it */
        send_expressions_to_add( results, peer );
    } else {
        send_work( input, peer );
    }    
}

/* W -> M: send the result of a computation */

void send_result( gi::ex T, MPI_Comm comm ){
    unsigned int len;
    char* expr_c;
    
    if( T.is_zero() ) {
        len = 0;
        expr_c = NULL;  // just so g++ does not complain that it believes we are using it uninitialized later
    } else {
        /* linearize the result */
        
        std::string expr = linearize_expression( T );
        
        /* Send it to the master */
        
        len = expr.length() + 1;
        expr_c = (char*) malloc( len );
        memcpy( expr_c, expr.c_str(), len-1 );
        expr_c[len-1] = '\0'; // C++ std::strings do not terminate with \0
    }
    
    MPI_Send( &len, 1, MPI_UNSIGNED, ROOT, TAG_RES, comm );
    if( len != 0 ) {        
        MPI_Send( expr_c, len, MPI_CHAR, ROOT, TAG_EXPR, comm );
        free( expr_c );
    }
    
}