reader_stepping.cpp

/*
 * reader.cpp
 *
 *  Created on: Feb 13, 2017
 *      Author: pnorbert
 */

#include <vector>
#include <iostream>

#include <mpi.h>
#include "ADIOS_CPP.h"


int main( int argc, char* argv [] )
{
    int rank, nproc;
    MPI_Init( &argc, &argv );
    MPI_Comm_rank( MPI_COMM_WORLD, &rank );
    MPI_Comm_size( MPI_COMM_WORLD, &nproc);
    const bool adiosDebug = true;

    adios::ADIOS adios( MPI_COMM_WORLD, adiosDebug );

    //Application variable
    std::vector<double> NiceArray;
    std::vector<float> RaggedArray;
    unsigned int Nx;
    int Nparts;
    int Nwriters;
    int Nsteps;

    try
    {
        //Define method for engine creation
        // 1. Get method def from config file or define new one
        adios::Method& bpReaderSettings = adios.GetMethod( "input" );
        if( bpReaderSettings.undeclared() )
        {
            // if not defined by user, we can change the default settings
            bpReaderSettings.SetEngine( "BP" ); // BP is the default engine
            bpReaderSettings.SetParameters ("Stepping", true); // see only one step at a time
        }

        //Create engine smart pointer due to polymorphism,
        // Default behavior
        // auto bpReader = adios.Open( "myNumbers.bp", "r" );
        // this would just open with a default transport, which is "BP"
        try
        {
            auto bpReader = adios.Open( "myNumbers.bp", "r", bpReaderSettings );

            while (true)
            {
                /* NX */
                bpReader->Read<unsigned int>( "NX", &Nx );  // read a Global scalar which has a single value in a step

                /* nproc */
                bpReader->Read<int>( "nproc", &Nwriters );  // also a global scalar


                /* Nparts */
                // Nparts local scalar is presented as a 1D array of Nwriters elements.
                // We can read all as a 1D array
                std::vector<int> partsV( Nwriters );
                bpReader->Read<int>( "Nparts", &partsV ); // read with string name, no selection => read whole array


                /* Nice */
                // inquiry about a variable, whose name we know
                std::shared_ptr<adios::Variable<void> > varNice = bpReader.InquiryVariable("Nice");

                if( varNice == nullptr )
                    throw std::ios_base::failure( "ERROR: failed to find variable 'myDoubles' in input file\n" );

                // ? how do we know about the type? std::string varNice->m_Type
                unsigned long long int gdim = varMyDoubles->m_GlobalDimensions[0];  // ?member var or member func?
                unsigned long long int ldim = gdim / nproc;
                unsigned long long int offs = rank * ldim;
                if( rank == nproc-1 )
                {
                    ldim = gdim - (ldim * gdim);
                }

                NiceArray.reserve(ldim);

                // Make a 1D selection to describe the local dimensions of the variable we READ and
                // its offsets in the global spaces
                std::unique_ptr<adios::Selection> bbsel = adios.SelectionBoundingBox( {ldim}, {offs} ); // local dims and offsets; both as list
                varNice->SetSelection( bbsel );
                bpReader->Read<double>( varNice, NiceArray.data() );


                /* Ragged */
                // inquiry about a variable, whose name we know
                std::shared_ptr<adios::Variable<void> > varRagged = bpReader.InquiryVariable("Ragged");
                if( varRagged->m_GlobalDimensions[1] != adios::VARYING_DIMENSION)
                {
                    throw std::ios_base::failure( "Unexpected condition: Ragged array's fast dimension "
                            "is supposed to be VARYING_DIMENSION\n" );
                }
                // We have here varRagged->sum_nblocks, nsteps, nblocks[], global
                if( rank < varRagged->nblocks[0] ) // same as rank < Nwriters in this example
                {
                    // get per-writer size information
                    varRagged->InquiryBlocks();
                    // now we have the dimensions per block

                    unsigned long long int ldim = varRagged->blockinfo[rank].m_Dimensions[0];
                    RaggedArray.resize( ldim );

                    std::unique_ptr<adios::Selection> wbsel = adios.SelectionWriteblock( rank );
                    varRagged->SetSelection( wbsel );
                    bpReader->Read<float>( varRagged, RaggedArray.data() );

                    // We can use bounding box selection as well
                    std::unique_ptr<adios::Selection> rbbsel = adios.SelectionBoundingBox( {1,ldim}, {rank,0} );
                    varRagged->SetSelection( rbbsel );
                    bpReader->Read<float>( varRagged, RaggedArray.data() );
                }

                /* Extra help to process Ragged */
                int maxRaggedDim = varRagged->GetMaxGlobalDimensions(1); // contains the largest
                std::vector<int> raggedDims = varRagged->GetVaryingGlobalDimensions(1); // contains all individual sizes in that dimension



                // promise to not read more from this step
                bpReader->Release();

                // want to move on to the next available step
                //bpReader->Advance(adios::NextStep);
                //bpReader->Advance(adios::LatestStep);
                bpReader->Advance(); // default is adios::NextStep

            }

            // Close file/stream
            bpReader->Close();

        }
        catch( adios::end_of_stream& e )
        {
            if( rank == 0 )
            {
                std::cout << "Reached end of stream, end processing loop.\n";
            }
            // Close file/stream
            bpReader->Close();
        }
        catch( adios::file_not_found& e )
        {
            if( rank == 0 )
            {
                std::cout << "File/stream does not exist, quit.\n";
            }
        }
    }
    catch( std::invalid_argument& e )
    {
        if( rank == 0 )
        {
            std::cout << "Invalid argument exception, STOPPING PROGRAM\n";
            std::cout << e.what() << "\n";
        }
    }
    catch( std::ios_base::failure& e )
    {
        if( rank == 0 )
        {
            std::cout << "System exception, STOPPING PROGRAM\n";
            std::cout << e.what() << "\n";
        }
    }
    catch( std::exception& e )
    {
        if( rank == 0 )
        {
            std::cout << "Exception, STOPPING PROGRAM\n";
            std::cout << e.what() << "\n";
        }
    }

    MPI_Finalize( );

    return 0;

}