Ejemplo n.º 1
0
  // Compute Y := alpha Op X + beta Y.
  //
  // We ignore the cases alpha != 1 and beta != 0 for simplicity.
  void
  apply (const MV& X,
         MV& Y,
         Teuchos::ETransp mode = Teuchos::NO_TRANS,
         scalar_type alpha = Teuchos::ScalarTraits<scalar_type>::one (),
         scalar_type beta = Teuchos::ScalarTraits<scalar_type>::zero ()) const
  {
    using Teuchos::RCP;
    using Teuchos::rcp;
    using std::cout;
    using std::endl;
    typedef Teuchos::ScalarTraits<scalar_type> STS;

    RCP<const Teuchos::Comm<int> > comm = opMap_->getComm ();
    const int myRank = comm->getRank ();
    const int numProcs = comm->getSize ();

    if (myRank == 0) {
      cout << "MyOp::apply" << endl;
    }

    // We're writing the Operator subclass, so we are responsible for
    // error handling.  You can decide how much error checking you
    // want to do.  Just remember that checking things like Map
    // sameness or compatibility are expensive.
    TEUCHOS_TEST_FOR_EXCEPTION(
      X.getNumVectors () != Y.getNumVectors (), std::invalid_argument,
      "X and Y do not have the same numbers of vectors (columns).");

    // Let's make sure alpha is 1 and beta is 0...
    // This will throw an exception if that is not the case.
    TEUCHOS_TEST_FOR_EXCEPTION(
      alpha != STS::one() || beta != STS::zero(), std::logic_error,
      "MyOp::apply was given alpha != 1 or beta != 0. "
      "These cases are not implemented.");

    // Get the number of vectors (columns) in X (and Y).
    const size_t numVecs = X.getNumVectors ();

    // Make a temporary multivector for holding the redistributed
    // data.  You could also create this in the constructor and reuse
    // it across different apply() calls, but you would need to be
    // careful to reallocate if it has a different number of vectors
    // than X.  The number of vectors in X can vary across different
    // apply() calls.
    RCP<MV> redistData = rcp (new MV (redistMap_, numVecs));

    // Redistribute the data.
    // This will do all the necessary communication for you.
    // All processes now own enough data to do the matvec.
    redistData->doImport (X, *importer_, Tpetra::INSERT);

    // Get the number of local rows in X, on the calling process.
    const local_ordinal_type nlocRows =
      static_cast<local_ordinal_type> (X.getLocalLength ());

    // Perform the matvec with the data we now locally own.
    //
    // For each column...
    for (size_t c = 0; c < numVecs; ++c) {
      // Get a view of the desired column
      Teuchos::ArrayRCP<scalar_type> colView = redistData->getDataNonConst (c);

      local_ordinal_type offset;
      // Y[0,c] = -colView[0] + 2*colView[1] - colView[2] (using local indices)
      if (myRank > 0) {
        Y.replaceLocalValue (0, c, -colView[0] + 2*colView[1] - colView[2]);
        offset = 0;
      }
      // Y[0,c] = 2*colView[1] - colView[2] (using local indices)
      else {
        Y.replaceLocalValue (0, c, 2*colView[0] - colView[1]);
        offset = 1;
      }

      // Y[r,c] = -colView[r-offset] + 2*colView[r+1-offset] - colView[r+2-offset]
      for (local_ordinal_type r = 1; r < nlocRows - 1; ++r) {
        const scalar_type newVal =
          -colView[r-offset] + 2*colView[r+1-offset] - colView[r+2-offset];
        Y.replaceLocalValue (r, c, newVal);
      }
      // Y[nlocRows-1,c] = -colView[nlocRows-1-offset] + 2*colView[nlocRows-offset]
      //                   - colView[nlocRows+1-offset]
      if (myRank < numProcs - 1) {
        const scalar_type newVal =
          -colView[nlocRows-1-offset] + 2*colView[nlocRows-offset]
          - colView[nlocRows+1-offset];
        Y.replaceLocalValue (nlocRows-1, c, newVal);
      }
      // Y[nlocRows-1,c] = -colView[nlocRows-1-offset] + 2*colView[nlocRows-offset]
      else {
        const scalar_type newVal =
          -colView[nlocRows-1-offset] + 2*colView[nlocRows-offset];
        Y.replaceLocalValue (nlocRows-1, c, newVal);
      }
    }
  }
Ejemplo n.º 2
0
  //
  // Computes Y = alpha Op X + beta Y
  // TraceMin will never use alpha ~= 1 or beta ~= 0,
  // so we have ignored those options for simplicity.
  //
  void apply(const MV& X, MV& Y, Teuchos::ETransp mode=Teuchos::NO_TRANS, Scalar alpha=SCT::one(), Scalar beta=SCT::zero()) const
  {
    //
    // Let's make sure alpha is 1 and beta is 0...
    // This will throw an exception if that is not the case.
    //
    TEUCHOS_TEST_FOR_EXCEPTION(alpha != SCT::one() || beta != SCT::zero(),std::invalid_argument,
           "MyOp::apply was given alpha != 1 or beta != 0. That's not supposed to happen.");

    //
    // Get the number of local rows
    //
    int nlocRows = X.getLocalLength();

    //
    // Get the number of vectors
    //
    int numVecs = X.getNumVectors();

    //
    // Make a multivector for holding the redistributed data
    //
    RCP<MV> redistData = rcp(new MV(redistMap_, numVecs));

    //
    // Redistribute the data.
    // This will do all the necessary communication for you.
    // All processes now own enough data to do the matvec.
    //
    redistData->doImport(X, *importer_, Tpetra::INSERT);

    //
    // Perform the matvec with the data we now locally own
    //
    // For each column...
    for(int c=0; c<numVecs; c++)
    {
      // Get a view of the desired column
      Teuchos::ArrayRCP<Scalar> colView = redistData->getDataNonConst(c); 

      int offset;
      // Y[0,c] = -colView[0] + 2*colView[1] - colView[2] (using local indices)
      if(myRank_ > 0)
      {
        Y.replaceLocalValue(0, c, -colView[0] + 2*colView[1] - colView[2]);
        offset = 0;
      }
      // Y[0,c] = 2*colView[1] - colView[2] (using local indices)
      else
      {
        Y.replaceLocalValue(0, c, 2*colView[0] - colView[1]);
        offset = 1;
      }
      
      // Y[r,c] = -colView[r-offset] + 2*colView[r+1-offset] - colView[r+2-offset]
      for(int r=1; r<nlocRows-1; r++)
      {
        Y.replaceLocalValue(r, c, -colView[r-offset] + 2*colView[r+1-offset] - colView[r+2-offset]);
      }

      // Y[nlocRows-1,c] = -colView[nlocRows-1-offset] + 2*colView[nlocRows-offset] - colView[nlocRows+1-offset]
      if(myRank_ < numProcs_-1)
      {
        Y.replaceLocalValue(nlocRows-1, c, -colView[nlocRows-1-offset] + 2*colView[nlocRows-offset] - colView[nlocRows+1-offset]);
      }
      // Y[nlocRows-1,c] = -colView[nlocRows-1-offset] + 2*colView[nlocRows-offset]
      else
      {
        Y.replaceLocalValue(nlocRows-1, c, -colView[nlocRows-1-offset] + 2*colView[nlocRows-offset]);
      }
    }
  }