Tpetra_Details_ReadTriples.hpp

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// @HEADER
// *****************************************************************************
//          Tpetra: Templated Linear Algebra Services Package
//
// Copyright 2008 NTESS and the Tpetra contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER
 
#ifndef TPETRA_DETAILS_READTRIPLES_HPP
#define TPETRA_DETAILS_READTRIPLES_HPP

 
#include "TpetraCore_config.h"
#include "Tpetra_Details_PackTriples.hpp"
#include "KokkosKernels_ArithTraits.hpp"
#include "Teuchos_MatrixMarket_generic.hpp"
#include "Teuchos_CommHelpers.hpp"
#include <iostream>
#include <typeinfo>  // for debugging
 
namespace Tpetra {
namespace Details {
 
//
// Search for "SKIP DOWN TO HERE" (omit quotes) for the "public"
// interface.  I put "public" in quotes because it's public only for
// Tpetra developers, NOT for Tpetra users.
//
 
namespace Impl {
 
// mfh 01 Feb 2017: Unfortunately,
// Teuchos::MatrixMarket::readComplexData requires Teuchos to have
// complex arithmetic support enabled.  To avoid this issue, I
// reimplement the function here.  It's not very long.

template <class OrdinalType, class RealType>
bool readComplexData(std::istream& istr,
                     OrdinalType& rowIndex,
                     OrdinalType& colIndex,
                     RealType& realPart,
                     RealType& imagPart,
                     const std::size_t lineNumber,
                     const bool tolerant) {
  using ::Teuchos::MatrixMarket::readRealData;
 
  RealType the_realPart, the_imagPart;
  if (!readRealData(istr, rowIndex, colIndex, the_realPart, lineNumber, tolerant)) {
    if (tolerant) {
      return false;
    } else {
      std::ostringstream os;
      os << "Failed to read pattern data and/or real value from line "
         << lineNumber << " of input";
      throw std::invalid_argument(os.str());
    }
  }
  if (istr.eof()) {
    if (tolerant) {
      return false;
    } else {
      std::ostringstream os;
      os << "No more data after real value on line "
         << lineNumber << " of input";
      throw std::invalid_argument(os.str());
    }
  }
  istr >> the_imagPart;
  if (istr.fail()) {
    if (tolerant) {
      return false;
    } else {
      std::ostringstream os;
      os << "Failed to get imaginary value from line "
         << lineNumber << " of input";
      throw std::invalid_argument(os.str());
    }
  }
  realPart = the_realPart;
  imagPart = the_imagPart;
  return true;
}

template <class SC,
          class GO,
          const bool isComplex = ::KokkosKernels::ArithTraits<SC>::is_complex>
struct ReadLine {
  static int
  readLine(std::function<int(const GO, const GO, const SC&)> processTriple,
           const std::string& line,
           const std::size_t lineNumber,
           const bool tolerant   = false,
           std::ostream* errStrm = NULL,
           const bool debug      = false);
};

template <class SC, class GO>
struct ReadLine<SC, GO, true> {
  static int
  readLine(std::function<int(const GO, const GO, const SC&)> processTriple,
           const std::string& line,
           const std::size_t lineNumber,
           const bool tolerant   = false,
           std::ostream* errStrm = NULL,
           const bool debug      = false) {
    using ::Teuchos::MatrixMarket::checkCommentLine;
    typedef typename ::KokkosKernels::ArithTraits<SC>::mag_type real_type;
    using std::endl;
 
    GO rowInd, colInd;
    real_type realPart, imagPart;
    std::istringstream istr(line);
    bool success = true;
    try {
      // Use the version of this function in this file, not the
      // version in Teuchos_MatrixMarket_generic.hpp, because the
      // latter only exists if HAVE_TEUCHOS_COMPLEX is defined.
      success = readComplexData(istr, rowInd, colInd, realPart, imagPart,
                                lineNumber, tolerant);
    } catch (std::exception& e) {
      success = false;
      if (errStrm != NULL) {
        std::ostringstream os;
        os << "readLine: readComplexData threw an exception: " << e.what()
           << endl;
        *errStrm << os.str();
      }
    }
 
    if (success) {
      // if (debug && errStrm != NULL) {
      //   std::ostringstream os;
      //   os << "readLine: Got entry: row=" << rowInd << ", col=" << colInd
      //      << ", realPart=" << realPart << ", imagPart=" << imagPart
      //      << std::endl;
      //   *errStrm << os.str ();
      // }
      // This line may have side effects.
      const int errCode =
          processTriple(rowInd, colInd, SC(realPart, imagPart));
      if (errCode != 0 && errStrm != NULL) {
        std::ostringstream os;
        os << "readLine: processTriple returned " << errCode << " != 0."
           << endl;
        *errStrm << os.str();
      }
      return errCode;
    } else {
      return -1;
    }
  }
};

template <class SC, class GO>
struct ReadLine<SC, GO, false> {
  static int
  readLine(std::function<int(const GO, const GO, const SC&)> processTriple,
           const std::string& line,
           const std::size_t lineNumber,
           const bool tolerant   = false,
           std::ostream* errStrm = NULL,
           const bool debug      = false) {
    using std::endl;
    using ::Teuchos::MatrixMarket::checkCommentLine;
    using ::Teuchos::MatrixMarket::readRealData;
 
    GO rowInd, colInd;
    SC val;
    std::istringstream istr(line);
    bool success = true;
    try {
      success = readRealData(istr, rowInd, colInd, val,
                             lineNumber, tolerant);
    } catch (std::exception& e) {
      success = false;
      if (errStrm != NULL) {
        std::ostringstream os;
        os << "readLine: readRealData threw an exception: " << e.what()
           << endl;
        *errStrm << os.str();
      }
    }
 
    if (success) {
      if (debug && errStrm != NULL) {
        std::ostringstream os;
        os << "readLine: Got entry: row=" << rowInd << ", col=" << colInd
           << ", val=" << val << std::endl;
        *errStrm << os.str();
      }
      // This line may have side effects.
      const int errCode = processTriple(rowInd, colInd, val);
      if (errCode != 0 && errStrm != NULL) {
        std::ostringstream os;
        os << "readLine: processTriple returned " << errCode << " != 0."
           << endl;
        *errStrm << os.str();
      }
      return errCode;
    } else {
      return -1;
    }
  }
};

template <class SC, class GO>
int readLine(std::function<int(const GO, const GO, const SC&)> processTriple,
             const std::string& line,
             const std::size_t lineNumber,
             const bool tolerant   = false,
             std::ostream* errStrm = NULL,
             const bool debug      = false) {
  return ReadLine<SC, GO>::readLine(processTriple, line, lineNumber,
                                    tolerant, errStrm, debug);
}

template <class SC, class GO>
int readTriples(std::istream& inputStream,
                std::size_t& curLineNum,
                std::size_t& numTriplesRead,
                std::function<int(const GO, const GO, const SC&)> processTriple,
                const std::size_t maxNumTriplesToRead,
                const bool tolerant   = false,
                std::ostream* errStrm = NULL,
                const bool debug      = false) {
  using std::endl;
  using std::size_t;
  using Teuchos::MatrixMarket::checkCommentLine;
 
  numTriplesRead = 0;  // output argument only
  if (inputStream.eof()) {
    return 0;  // no error, just nothing left to read
  } else if (inputStream.fail()) {
    if (errStrm != NULL) {
      *errStrm << "Input stream reports a failure (not the same as "
                  "end-of-file)."
               << endl;
    }
    return -1;
  }
 
  std::string line;
  std::vector<size_t> badLineNumbers;
  int errCode = 0;  // 0 means success
 
  bool inputStreamCanStillBeRead = std::getline(inputStream, line).good();
  ++curLineNum;  // we read the line; we can't put it back
  while (inputStreamCanStillBeRead && numTriplesRead < maxNumTriplesToRead) {
    // if (debug && errStrm != NULL) {
    //   std::ostringstream os;
    //   os << "readTriples: Got line: \"" << line << "\"" << std::endl;
    //   *errStrm << os.str ();
    // }
    size_t start, size;
 
    const bool isCommentLine =
        checkCommentLine(line, start, size, curLineNum, tolerant);
    if (isCommentLine) {
      // Move on to the next line, if there is a next line.
      inputStreamCanStillBeRead = std::getline(inputStream, line).good();
      ++curLineNum;  // we read another line; we can't put it back
      continue;      // move on to the next line
    } else {         // not a comment line; should have a sparse matrix entry
      const std::string theLine = line.substr(start, size);
      // If the line has a valid sparse matrix entry, extract it and
      // hand it off to the processTriple closure.
      const int curErrCode =
          readLine(processTriple, theLine, curLineNum, tolerant, errStrm, debug);
      if (curErrCode != 0) {
        errCode = curErrCode;
        badLineNumbers.push_back(curLineNum);
      } else {
        ++numTriplesRead;
      }
      if (numTriplesRead < maxNumTriplesToRead) {
        inputStreamCanStillBeRead = std::getline(inputStream, line).good();
      }
    }
  }  // while there are lines to read and we need more triples
 
  if (errCode != 0 && errStrm != NULL) {
    const size_t numBadLines = badLineNumbers.size();
    *errStrm << "Encountered " << numBadLines << " bad line"
             << (numBadLines != size_t(1) ? "s" : "")
             << ": [";
    for (size_t k = 0; k < numBadLines; ++k) {
      *errStrm << badLineNumbers[k];
      if (k + 1 < numBadLines) {
        *errStrm << ", ";
      }
    }
    *errStrm << "]" << endl;
  }
  if (!inputStream.eof() && inputStream.fail()) {
    if (errCode == 0) {
      errCode = -1;
    }
    if (errStrm != NULL) {
      *errStrm << "The input stream is not at end-of-file, "
                  "but is in a bad state."
               << endl;
    }
  }
  return errCode;
}

template <class SC, class GO>
int readAndSendOneBatchOfTriples(std::istream& inputStream,
                                 std::size_t& curLineNum,
                                 std::size_t& numEntRead,
                                 ::Teuchos::ArrayRCP<int>& sizeBuf,
                                 ::Teuchos::ArrayRCP<char>& msgBuf,
                                 std::vector<GO>& rowInds,
                                 std::vector<GO>& colInds,
                                 std::vector<SC>& vals,
                                 const std::size_t maxNumEntPerMsg,
                                 const int destRank,
                                 const ::Teuchos::Comm<int>& comm,
                                 const bool tolerant   = false,
                                 std::ostream* errStrm = NULL,
                                 const bool debug      = false) {
  using std::endl;
  using ::Teuchos::isend;
  using ::Tpetra::Details::countPackTriples;
  using ::Tpetra::Details::countPackTriplesCount;
  using ::Tpetra::Details::packTriples;
  using ::Tpetra::Details::packTriplesCount;
 
  using ::KokkosKernels::ArithTraits;
  // constexpr int sizeTag = 42 + (ArithTraits<SC>::is_complex ? 100 : 0);
  // constexpr int msgTag = 43 + (ArithTraits<SC>::is_complex ? 100 : 0);
  constexpr int sizeTag = 42;
  constexpr int msgTag  = 43;
  // constexpr int srcRank = 0;
  int errCode = 0;
 
  // This doesn't actually deallocate memory; it just changes the size
  // back to zero, so that push_back starts over from the beginning.
  rowInds.resize(0);
  colInds.resize(0);
  vals.resize(0);
  // Closure that adds the new matrix entry to the above temp arrays.
  auto processTriple = [&rowInds, &colInds, &vals](const GO rowInd, const GO colInd, const SC& val) {
    try {
      rowInds.push_back(rowInd);
      colInds.push_back(colInd);
      vals.push_back(val);
    } catch (...) {
      return -1;
    }
    return 0;
  };
  numEntRead = 0;  // output argument
  errCode    = readTriples<SC, GO>(inputStream, curLineNum, numEntRead,
                                processTriple, maxNumEntPerMsg, tolerant,
                                errStrm, debug);
  if (debug && errStrm != NULL) {
    std::ostringstream os;
    os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
       << ", GO=" << typeid(GO).name() << ": "
       << "readAndSendOneBatchOfTriples: readTriples read "
       << numEntRead << " matrix entries, and returned errCode="
       << errCode << "." << std::endl;
    *errStrm << os.str();
  }
  if (numEntRead != rowInds.size() ||
      numEntRead != colInds.size() ||
      numEntRead != vals.size()) {
    if (errStrm != NULL) {
      *errStrm << "readTriples size results are not consistent.  "
               << "numEntRead = " << numEntRead
               << ", rowInds.size() = " << rowInds.size()
               << ", colInds.size() = " << colInds.size()
               << ", and vals.size() = " << vals.size() << "."
               << std::endl;
    }
    if (errCode == 0) {
      errCode = -1;
    }
  }
 
  // We don't consider reading having "failed" if we've reached
  // end-of-file before reading maxNumEntPerMsg entries.  It's OK if
  // we got fewer triples than that.  Furthermore, we have to send at
  // least one message to the destination process, even if the read
  // from the file failed.
 
  if (numEntRead == 0 || errCode != 0) {
    // Send a message size of zero to the receiving process, to tell
    // it that we have no triples to send, or that there was an error
    // reading.  The latter just means that we "go through the
    // motions," then broadcast the error code.
    sizeBuf[0] = 0;
    if (debug && errStrm != NULL) {
      std::ostringstream os;
      os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
         << ", GO=" << typeid(GO).name() << ": "
         << "Post send (size=0, errCode=" << errCode << ") "
         << "to " << destRank << " with tag " << sizeTag << endl;
      *errStrm << os.str();
    }
    send(sizeBuf.getRawPtr(), 1, destRank, sizeTag, comm);
    return errCode;
  } else {  // we read a nonzero # of triples, without error
    const int numEnt = static_cast<int>(numEntRead);
    int countSize    = 0;  // output argument
    int triplesSize  = 0;  // output argument
 
    errCode = countPackTriplesCount(comm, countSize, errStrm);
    // countSize should never be nonpositive, since we have to pack an
    // integer size.
    if (countSize <= 0 && errCode == 0) {
      errCode = -1;
    }
 
    if (errCode != 0) {
      // Send zero to the receiving process, to tell it about the error.
      sizeBuf[0] = 0;
      if (debug && errStrm != NULL) {
        std::ostringstream os;
        os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
           << ", GO=" << typeid(GO).name() << ": "
           << "Post send (size=0, error case) to " << destRank
           << " with tag " << sizeTag << endl;
        *errStrm << os.str();
      }
      send(sizeBuf.getRawPtr(), 1, destRank, sizeTag, comm);
      return errCode;
    } else {  // countPackTriplesCount succeeded
      errCode = countPackTriples<SC, GO>(numEnt, comm, triplesSize, errStrm);
      if (errCode != 0) {
        // Send a message size of zero to the receiving process, to
        // tell it that there was an error counting.
        sizeBuf[0] = 0;
        if (debug && errStrm != NULL) {
          std::ostringstream os;
          os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
             << ", GO=" << typeid(GO).name() << ": "
             << "Post send (size=0, error case) to " << destRank
             << " with tag " << sizeTag << endl;
          *errStrm << os.str();
        }
        send(sizeBuf.getRawPtr(), 1, destRank, sizeTag, comm);
        return errCode;
      } else {  // countPackTriples succeeded; message packed & ready to send
        // Send the message size (in bytes).  We can use a nonblocking
        // send here, and try to overlap with message packing.
        const int outBufSize = countSize + triplesSize;
        sizeBuf[0]           = outBufSize;
        if (debug && errStrm != NULL) {
          std::ostringstream os;
          os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
             << ", GO=" << typeid(GO).name() << ": "
             << "Post isend (size=" << sizeBuf[0] << ") to " << destRank
             << " with tag " << sizeTag << endl;
          *errStrm << os.str();
        }
        auto sizeReq = isend<int, int>(sizeBuf, destRank, sizeTag, comm);
 
        msgBuf.resize(outBufSize);
        char* outBuf = msgBuf.getRawPtr();
 
        // If anything goes wrong with packing, send the pack buffer
        // anyway, since the receiving process expects a message.
        int outBufCurPos = 0;  // input/output argument
        errCode          = packTriplesCount(numEnt, outBuf, outBufSize,
                                            outBufCurPos, comm, errStrm);
        if (errCode == 0) {
          errCode = packTriples<SC, GO>(rowInds.data(), colInds.data(),
                                        vals.data(), numEnt, outBuf,
                                        outBufSize, outBufCurPos, comm,
                                        errStrm);
        }
        if (debug && errStrm != NULL) {
          std::ostringstream os;
          os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
             << ", GO=" << typeid(GO).name() << ": "
             << "Post isend (packed data) to " << destRank
             << " with tag " << msgTag << endl;
          *errStrm << os.str();
        }
        auto msgReq = isend<int, char>(msgBuf, destRank, msgTag, comm);
 
        // Wait on the two messages.  It doesn't matter in what order
        // we send them, because they have different tags.  The
        // receiving process will wait on the first message first, in
        // order to get the size of the second message.
        if (debug && errStrm != NULL) {
          std::ostringstream os;
          os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
             << ", GO=" << typeid(GO).name() << ": "
             << "Wait on isend (size)" << endl;
          *errStrm << os.str();
        }
        sizeReq->wait();
        if (debug && errStrm != NULL) {
          std::ostringstream os;
          os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
             << ", GO=" << typeid(GO).name() << ": "
             << "Wait on isend (packed data)" << endl;
          *errStrm << os.str();
        }
        msgReq->wait();
 
        // This doesn't actually deallocate; it just resets sizes to zero.
        rowInds.clear();
        colInds.clear();
        vals.clear();
      }
    }
  }
  return errCode;
}


template <class SC, class GO, class CommRequestPtr>
int recvOneBatchOfTriples(std::vector<GO>& rowInds,
                          std::vector<GO>& colInds,
                          std::vector<SC>& vals,
                          int& numEnt,
                          ::Teuchos::ArrayRCP<int>& sizeBuf,
                          ::Teuchos::ArrayRCP<char>& msgBuf,
                          CommRequestPtr& sizeReq,
                          const int srcRank,
                          const ::Teuchos::Comm<int>& comm,
                          const bool tolerant   = false,
                          std::ostream* errStrm = NULL,
                          const bool debug      = false) {
  using ::KokkosKernels::ArithTraits;
  using ::Tpetra::Details::unpackTriples;
  using ::Tpetra::Details::unpackTriplesCount;

  // constexpr int msgTag = 43 + (ArithTraits<SC>::is_complex ? 100 : 0);
  // constexpr int sizeTag = 42;
  constexpr int msgTag = 43;
  int errCode          = 0;  // return value
  numEnt               = 0;  // output argument
 
  // Wait on the ireceive we preposted before calling this function.
  if (debug && errStrm != NULL) {
    std::ostringstream os;
    os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
       << ", GO=" << typeid(GO).name() << ": "
       << "Wait on irecv (size)" << std::endl;
    *errStrm << os.str();
  }
  sizeReq->wait();
  sizeReq             = CommRequestPtr(NULL);
  const int inBufSize = sizeBuf[0];
  if (debug && errStrm != NULL) {
    std::ostringstream os;
    os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
       << ", GO=" << typeid(GO).name() << ": "
       << "Received size: sizeBuf[0]=" << sizeBuf[0] << std::endl;
    *errStrm << os.str();
  }
 
  if (inBufSize == 0) {
    numEnt = 0;
    rowInds.resize(0);
    colInds.resize(0);
    vals.resize(0);
  } else {
    msgBuf.resize(inBufSize);
    char* inBuf = msgBuf.getRawPtr();
 
    if (debug && errStrm != NULL) {
      std::ostringstream os;
      os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
         << ", GO=" << typeid(GO).name() << ": "
         << "Post irecv (packed data) "
         << "from " << srcRank
         << " with tag " << msgTag << std::endl;
      *errStrm << os.str();
    }
    auto msgReq = ::Teuchos::ireceive(msgBuf, srcRank, msgTag, comm);
    if (debug && errStrm != NULL) {
      std::ostringstream os;
      os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
         << ", GO=" << typeid(GO).name() << ": "
         << "Wait on irecv (packed data)" << std::endl;
      *errStrm << os.str();
    }
    msgReq->wait();
 
    int inBufCurPos = 0;  // output argument
    errCode         = unpackTriplesCount(inBuf, inBufSize, inBufCurPos,
                                         numEnt, comm, errStrm);
    if (errCode == 0) {
      rowInds.resize(numEnt);
      colInds.resize(numEnt);
      vals.resize(numEnt);
      errCode = unpackTriples<SC, GO>(inBuf, inBufSize, inBufCurPos,
                                      rowInds.data(), colInds.data(),
                                      vals.data(), numEnt, comm, errStrm);
    }
  }
  return errCode;
}
 
}  // namespace Impl
 
//
// SKIP DOWN TO HERE FOR "PUBLIC" INTERFACE
//

template <class SC, class GO>
int readAndDealOutTriples(std::istream& inputStream,     // only valid on Proc 0
                          std::size_t& curLineNum,       // only valid on Proc 0
                          std::size_t& totalNumEntRead,  // only valid on Proc 0
                          std::function<int(const GO, const GO, const SC&)> processTriple,
                          const std::size_t maxNumEntPerMsg,
                          const ::Teuchos::Comm<int>& comm,
                          const bool tolerant   = false,
                          std::ostream* errStrm = NULL,
                          const bool debug      = false) {
  using KokkosKernels::ArithTraits;
  using std::endl;
  using std::size_t;
 
  constexpr int srcRank = 0;
  // constexpr int sizeTag = 42 + (ArithTraits<SC>::is_complex ? 100 : 0);
  constexpr int sizeTag = 42;
  // constexpr int msgTag = 43;
  const int myRank   = comm.getRank();
  const int numProcs = comm.getSize();
  int errCode        = 0;
 
  ::Teuchos::ArrayRCP<int> sizeBuf(1);
  ::Teuchos::ArrayRCP<char> msgBuf;  // to be resized as needed
 
  // Temporary storage for reading & packing (on Process srcRank) or
  // unpacking (every other process) triples.
  std::vector<GO> rowInds;
  std::vector<GO> colInds;
  std::vector<SC> vals;
  rowInds.reserve(maxNumEntPerMsg);
  colInds.reserve(maxNumEntPerMsg);
  vals.reserve(maxNumEntPerMsg);
 
  totalNumEntRead = 0;
  if (myRank == srcRank) {
    // Loop around through all the processes, including this one, over
    // and over until we reach the end of the file, or an error occurs.
    int destRank                 = 0;
    bool lastMessageWasLegitZero = false;
    for (;
         !inputStream.eof() && errCode == 0;
         destRank = (destRank + 1) % numProcs) {
      size_t curNumEntRead = 0;  // output argument of below
      if (destRank == srcRank) {
        // We can read and process the triples directly.  We don't
        // need to use intermediate storage, because we don't need to
        // pack and send the triples.
        const int readErrCode =
            Impl::readTriples<SC, GO>(inputStream, curLineNum, curNumEntRead,
                                      processTriple, maxNumEntPerMsg, tolerant,
                                      errStrm, debug);
        if (debug && errStrm != NULL) {
          std::ostringstream os;
          os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
             << ", GO=" << typeid(GO).name() << ": "
             << "(dest=src) readTriples returned curNumEntRead="
             << curNumEntRead << ", errCode=" << readErrCode << endl;
          *errStrm << os.str();
        }
        errCode = (readErrCode != 0) ? readErrCode : errCode;
      } else {
        if (false && debug && errStrm != NULL) {
          std::ostringstream os;
          os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
             << ", GO=" << typeid(GO).name() << ": "
             << "Calling readAndSend... with destRank=" << destRank << endl;
          *errStrm << os.str();
        }
        // Read, pack, and send the triples to destRank.
        const int readAndSendErrCode =
            Impl::readAndSendOneBatchOfTriples<SC, GO>(inputStream, curLineNum,
                                                       curNumEntRead,
                                                       sizeBuf, msgBuf,
                                                       rowInds, colInds, vals,
                                                       maxNumEntPerMsg, destRank,
                                                       comm, tolerant, errStrm,
                                                       debug);
        totalNumEntRead += curNumEntRead;
        if (debug && errStrm != NULL) {
          std::ostringstream os;
          os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
             << ", GO=" << typeid(GO).name() << ": "
             << "readAndSend... with destRank=" << destRank
             << " returned curNumEntRead=" << curNumEntRead
             << ", errCode=" << readAndSendErrCode << endl;
          *errStrm << os.str();
        }
        errCode = (readAndSendErrCode != 0) ? readAndSendErrCode : errCode;
        if (readAndSendErrCode == 0 && curNumEntRead == 0) {
          lastMessageWasLegitZero = true;
          if (debug && errStrm != NULL) {
            std::ostringstream os;
            os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
               << ", GO=" << typeid(GO).name() << ": "
               << "Last send to " << destRank << " with tag " << sizeTag
               << " was legit zero, counts as termination" << endl;
            *errStrm << os.str();
          }
        }
      }
    }  // loop around through processes until done reading file, or error
 
    // Loop around through the remaining processes, and tell them that
    // we're done, by sending zero.  If the last message we sent to
    // destRank was zero, then skip that process, since it only
    // expects one message of size zero.  Note that destRank got
    // incremented mod numProcs at end of loop, so we have to
    // decrement it mod numProcs.
    destRank = (destRank - 1) % numProcs;
    if (destRank < 0) {  // C mod operator does not promise positivity
      destRank = destRank + numProcs;
    }
 
    const int startRank = lastMessageWasLegitZero ? (destRank + 1) : destRank;
    for (int outRank = startRank; outRank < numProcs; ++outRank) {
      if (outRank != srcRank) {
        if (debug && errStrm != NULL) {
          std::ostringstream os;
          os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
             << ", GO=" << typeid(GO).name() << ": "
             << "Post send (size, termination msg) to " << outRank
             << " with tag " << sizeTag << "(was last message legit zero? "
             << (lastMessageWasLegitZero ? "true" : "false") << ")" << endl;
          *errStrm << os.str();
        }
        sizeBuf[0] = 0;
        ::Teuchos::send(sizeBuf.getRawPtr(), 1, outRank, sizeTag, comm);
      }
    }
  } else {
    while (true) {
      // Prepost a message to receive the size (in bytes) of the
      // incoming packet.
      sizeBuf[0] = 0;  // superfluous, but safe
      if (debug && errStrm != NULL) {
        std::ostringstream os;
        os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
           << ", GO=" << typeid(GO).name() << ": "
           << "Post irecv (size) from " << srcRank
           << " with tag " << sizeTag << std::endl;
        *errStrm << os.str();
      }
      auto sizeReq = ::Teuchos::ireceive(sizeBuf, srcRank, sizeTag, comm);
 
      int numEnt = 0;  // output argument
      const int recvErrCode =
          Impl::recvOneBatchOfTriples(rowInds, colInds, vals, numEnt, sizeBuf,
                                      msgBuf, sizeReq, srcRank, comm, tolerant,
                                      errStrm, debug);
      if (debug && errStrm != NULL) {
        std::ostringstream os;
        os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
           << ", GO=" << typeid(GO).name() << ": "
           << "recvOneBatchOfTriples returned numEnt=" << numEnt
           << ", errCode=" << recvErrCode << endl;
        *errStrm << os.str();
      }
      errCode = (recvErrCode != 0) ? recvErrCode : errCode;
 
      if (numEnt != static_cast<int>(rowInds.size()) ||
          numEnt != static_cast<int>(colInds.size()) ||
          numEnt != static_cast<int>(vals.size())) {
        errCode = (errCode == 0) ? -1 : errCode;
        if (errStrm != NULL) {
          *errStrm << "recvOneBatchOfTriples produced inconsistent data sizes.  "
                   << "numEnt = " << numEnt
                   << ", rowInds.size() = " << rowInds.size()
                   << ", colInds.size() = " << colInds.size()
                   << ", vals.size() = " << vals.size() << "."
                   << endl;
        }
      }  // if sizes inconsistent
 
      // Sending zero items is how Process srcRank tells this process
      // that it (Process srcRank) is done sending out data.
      if (numEnt == 0) {
        break;
      }
 
      for (int k = 0; k < numEnt && errCode == 0; ++k) {
        const int curErrCode = processTriple(rowInds[k], colInds[k], vals[k]);
        errCode              = (curErrCode == 0) ? errCode : curErrCode;
      }
    }  // while we still get messages from srcRank
  }
 
  if (debug && errStrm != NULL) {
    std::ostringstream os;
    os << "Proc " << comm.getRank() << ", SC=" << typeid(SC).name()
       << ", GO=" << typeid(GO).name() << ": "
       << "Done with send/recv loop" << endl;
    *errStrm << os.str();
  }
  // Do a bitwise OR to get an error code that is nonzero if and only
  // if any process' local error code is nonzero.
  using ::Teuchos::outArg;
  using ::Teuchos::REDUCE_BOR;
  using ::Teuchos::reduceAll;
  const int lclErrCode = errCode;
  reduceAll<int, int>(comm, REDUCE_BOR, lclErrCode, outArg(errCode));
  return errCode;
}
 
}  // namespace Details
}  // namespace Tpetra
 
#endif  // TPETRA_DETAILS_READTRIPLES_HPP