reader.cpp

/*
 * Distributed under the OSI-approved Apache License, Version 2.0.  See
 * accompanying file Copyright.txt for details.
 *
 * reader.cpp
 *
 *  Created on: Feb 13, 2017
 *      Author: pnorbert
 */

#include <iostream>
#include <vector>

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

  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
    }

    // 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"
    auto bpReader = adios.Open("myNumbers.bp", "r", bpReaderSettings);

    // All the above is same as default use:
    // auto bpReader = adios.Open( "myNumbers.bp", "r");

    if (bpReader == nullptr)
      throw std::ios_base::failure("ERROR: failed to open ADIOS bpReader\n");

    /* Variable names are available as a vector of strings */
    std::cout << "List of variables in file: " << bpReader->VariableNames
              << "\n";

    /* 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 need to read a specific value the same way as reading from any 1D
    // array.
    // Make a single-value selection to describe our rank's position in the
    // 1D array of Nwriters values.
    if (rank < Nwriters)
    {
      std::shared_ptr<adios::Variable> varNparts =
          bpReader.InquiryVariable("Nparts");
      std::unique_ptr<adios::Selection> selNparts =
          adios.SelectionBoundingBox({1}, {rank});
      varNparts->SetSelection(selNparts);
      bpReader->Read<int>(varNparts, Nparts);
    }
    // or we could just read the whole array by every process
    std::vector<int> partsV(Nwriters);
    bpReader->Read<int>(
        "Nparts",
        partsV
            .data()); // read with string name, no selection => read whole array

    std::vector<int> partsV;
    bpReader->Read<int>(
        "Nparts",
        partsV); // read with string name, no selection => read whole array
    (Nwriters == partsV.size())

        /* Nice */
        // inquiry about a variable, whose name we know
        std::shared_ptr<adios::Variable>
            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
    uint64_t gdim =
        varNice->m_GlobalDimensions[0]; // ?member var or member func?
    uint64_t ldim = gdim / nproc;
    uint64_t 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[1];
      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

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