MPI Datatybe Builder

example.cpp

#include <mpidatatypebuilder.h>
#include <mpi.h>


using namespace std;

struct DataSet {
    double vectorA[131072];
    double vectorB[131072];
    double arg1;
    double arg2;
};

int main(int argc, char** argv)
{

    // ...

    DataSet emptySet;
    MpiDatatypeBuilder builder(&emptySet, 4);
    builder
            .addVariable(&emptySet.vectorA, MPI_DOUBLE, 131072)
            ->addVariable(&emptySet.vectorB, MPI_DOUBLE, 131072)
            ->addVariable(&emptySet.arg1, MPI_DOUBLE, 1)
            ->addVariable(&emptySet.arg2, MPI_DOUBLE, 1);

    MPI_Datatype dataSetDatatype = builder.build();

    // ...

    return 0;
}

mpidatatypebuilder.cpp

#include "mpidatatypebuilder.h"

MpiDatatypeBuilder::MpiDatatypeBuilder(void *structure, int varCount)
{
    MPI_Get_address(structure, &this->base);
    this->dataSizes = new int[varCount];
    this->dataTypes = new MPI_Datatype[varCount];
    this->offsets = new MPI_Aint[varCount];
    this->curVar = 0;
}

MpiDatatypeBuilder::~MpiDatatypeBuilder()
{
    delete this->offsets;
    delete this->dataTypes;
    delete this->dataSizes;
}


MpiDatatypeBuilder* MpiDatatypeBuilder::addVariable(void *variablePtr, MPI_Datatype datatype, int count) {
    MPI_Get_address(variablePtr, &this->offsets[this->curVar]);
    this->offsets[this->curVar] -= this->base;
    this->dataTypes[this->curVar] = datatype;
    this->dataSizes[this->curVar] = count;

    this->curVar++;

    return this;
}


MPI_Datatype MpiDatatypeBuilder::build()
{
    MPI_Datatype datatype;
    MPI_Aint lb, range;

    MPI_Type_struct(this->curVar, this->dataSizes, this->offsets, this->dataTypes, &datatype);
    MPI_Type_get_extent(datatype, &lb, &range);
    MPI_Type_create_resized(datatype, lb, range, &datatype);
    MPI_Type_commit(&datatype);

    return datatype;
}

mpidatatypebuilder.h

#ifndef MPIDATATYPEBUILDER_H
#define MPIDATATYPEBUILDER_H

#include <mpi.h>

/**
 * @brief The MpiDatatypeBuilder class
 * @Author Piotr Rogowski <[email protected]>
 * @Licence CC BY-NC-SA 4.0 https://creativecommons.org/licenses/by-nc-sa/4.0/
 */
class MpiDatatypeBuilder
{
    int *dataSizes;
    MPI_Datatype *dataTypes;
    MPI_Aint *offsets;
    MPI_Aint base;
    int curVar;

public:
    MpiDatatypeBuilder(void* structure, int varCount);
    ~MpiDatatypeBuilder();

    MpiDatatypeBuilder* addVariable(void* variablePtr, MPI_Datatype datatype, int count);
    MPI_Datatype build();
};

#endif // MPIDATATYPEBUILDER_H