BelosPseudoBlockStochasticCGIter.hpp

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// @HEADER
// *****************************************************************************
//                 Belos: Block Linear Solvers Package
//
// Copyright 2004-2016 NTESS and the Belos contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER
 
#ifndef BELOS_PSEUDO_BLOCK_STOCHASTIC_CG_ITER_HPP
#define BELOS_PSEUDO_BLOCK_STOCHASTIC_CG_ITER_HPP
 
#include "BelosConfigDefs.hpp"
#include "BelosTypes.hpp"
#include "BelosStochasticCGIteration.hpp"
 
#include "BelosLinearProblem.hpp"
#include "BelosMatOrthoManager.hpp"
#include "BelosOutputManager.hpp"
#include "BelosStatusTest.hpp"
#include "BelosOperatorTraits.hpp"
#include "BelosMultiVecTraits.hpp"
 
#include "Teuchos_SerialDenseVector.hpp"
#include "Teuchos_SerialDenseHelpers.hpp"
#include "Teuchos_ScalarTraits.hpp"
#include "Teuchos_ParameterList.hpp"
#include "Teuchos_TimeMonitor.hpp"
 
namespace Belos {
  
  template<class ScalarType, class MV, class OP, class DM>
  class PseudoBlockStochasticCGIter : virtual public StochasticCGIteration<ScalarType,MV,OP,DM> {
    
  public:
    
    //
    // Convenience typedefs
    //
    typedef MultiVecTraits<ScalarType,MV,DM> MVT;
    typedef OperatorTraits<ScalarType,MV,OP> OPT;
    typedef DenseMatTraits<ScalarType,DM> DMT;
    typedef Teuchos::ScalarTraits<ScalarType> SCT;
    typedef typename SCT::magnitudeType MagnitudeType;
    
 
    
    PseudoBlockStochasticCGIter( const Teuchos::RCP<LinearProblem<ScalarType,MV,OP,DM> > &problem,
         const Teuchos::RCP<OutputManager<ScalarType> > &printer,
         const Teuchos::RCP<StatusTest<ScalarType,MV,OP,DM> > &tester,
         Teuchos::ParameterList &params );
    
    virtual ~PseudoBlockStochasticCGIter() {};
    
    
 
    
    void iterate();
    
    void initializeCG(StochasticCGIterationState<ScalarType,MV>& newstate);
    
    void initialize()
    {
      StochasticCGIterationState<ScalarType,MV> empty;
      initializeCG(empty);
    }
    
    StochasticCGIterationState<ScalarType,MV> getState() const {
      StochasticCGIterationState<ScalarType,MV> state;
      state.R = R_;
      state.P = P_;
      state.AP = AP_;
      state.Z = Z_;
      state.Y = Y_;
      return state;
    }
    
    
    
 
    
    int getNumIters() const { return iter_; }
    
    void resetNumIters( int iter = 0 ) { iter_ = iter; }
    
    Teuchos::RCP<const MV> getNativeResiduals( std::vector<MagnitudeType> * /* norms */ ) const { return R_; }
    
 
    Teuchos::RCP<MV> getCurrentUpdate() const { return Teuchos::null; }
    
    Teuchos::RCP<MV> getStochasticVector() const { return Y_; }
 
    
 
    
    const LinearProblem<ScalarType,MV,OP,DM>& getProblem() const { return *lp_; }
    
    int getBlockSize() const { return 1; }
    
    void setBlockSize(int blockSize) { 
      TEUCHOS_TEST_FOR_EXCEPTION(blockSize!=1,std::invalid_argument,
       "Belos::PseudoBlockStochasticCGIter::setBlockSize(): Cannot use a block size that is not one.");
    }
    
    bool isInitialized() { return initialized_; }
    
    
  private:
 
    inline Teuchos::SerialDenseVector<int,ScalarType>& normal() {
      // Do all of the calculations with doubles, because that is what the Odeh and Evans 1974 constants are for.
      // Then cast to ScalarType.
      
      const double p0 = -0.322232431088;
      const double p1 = -1.0;
      const double p2 = -0.342242088547; 
      const double p3 = -0.204231210245e-1;
      const double p4 = -0.453642210148e-4;
      const double q0 =  0.993484626060e-1;
      const double q1 =  0.588581570495;
      const double q2 =  0.531103462366;
      const double q3 =  0.103537752850;
      const double q4 =  0.38560700634e-2;
      double r,p,q,y,z;
 
      // Return a vector with random entries that are synchronized across processors.
      Teuchos::randomSyncedMatrix( randvec_ );
 
      for (int i=0; i<numRHS_; i++)
      {      
        // Get a random number (-1,1) and rescale to (0,1). 
        r=0.5*SCT::real(randvec_[i]) + 1.0;
      
        // Odeh and Evans algorithm (as modified by Park & Geyer)
        if(r < 0.5) y=std::sqrt(-2.0 * log(r));
        else y=std::sqrt(-2.0 * log(1.0 - r));
      
        p = p0 + y * (p1 + y* (p2 + y * (p3 + y * p4)));
        q = q0 + y * (q1 + y* (q2 + y * (q3 + y * q4)));
      
        if(r < 0.5) z = (p / q) - y;
        else z = y - (p / q);
      
        randvec_[i] = Teuchos::as<ScalarType,double>(z);
      }
 
      return randvec_;
    }
       
    //
    // Classes inputed through constructor that define the linear problem to be solved.
    //
    const Teuchos::RCP<LinearProblem<ScalarType,MV,OP,DM> >    lp_;
    const Teuchos::RCP<OutputManager<ScalarType> >          om_;
    const Teuchos::RCP<StatusTest<ScalarType,MV,OP,DM> >       stest_;
    
    //
    // Algorithmic parameters
    //  
    // numRHS_ is the current number of linear systems being solved.
    int numRHS_;
    
    // 
    // Current solver state
    //
    // initialized_ specifies that the basis vectors have been initialized and the iterate() routine
    // is capable of running; _initialize is controlled  by the initialize() member method
    // For the implications of the state of initialized_, please see documentation for initialize()
    bool initialized_;
    
    // Current number of iterations performed.
    int iter_;
 
    // Current number of iterations performed.
    bool assertPositiveDefiniteness_;
 
    // 
    // State Storage
    //
    // Residual
    Teuchos::RCP<MV> R_;
    //
    // Preconditioned residual
    Teuchos::RCP<MV> Z_;
    //
    // Direction vector
    Teuchos::RCP<MV> P_;
    //
    // Operator applied to direction vector
    Teuchos::RCP<MV> AP_;
    //
    // Stochastic recurrence vector
    Teuchos::RCP<MV> Y_;
    //
    // Stochastic variable storage (for normal() method)
    Teuchos::SerialDenseVector<int,ScalarType> randvec_;
 
  };
  
  // Constructor.
  template<class ScalarType, class MV, class OP, class DM>
  PseudoBlockStochasticCGIter<ScalarType,MV,OP,DM>::PseudoBlockStochasticCGIter(const Teuchos::RCP<LinearProblem<ScalarType,MV,OP,DM> > &problem,
                     const Teuchos::RCP<OutputManager<ScalarType> > &printer,
                     const Teuchos::RCP<StatusTest<ScalarType,MV,OP,DM> > &tester,
                     Teuchos::ParameterList &params ):
    lp_(problem),
    om_(printer),
    stest_(tester),
    numRHS_(0),
    initialized_(false),
    iter_(0),
    assertPositiveDefiniteness_( params.get("Assert Positive Definiteness", true) )
  {
  }
  
 
  // Initialize this iteration object
  template<class ScalarType, class MV, class OP, class DM>
  void PseudoBlockStochasticCGIter<ScalarType,MV,OP,DM>::initializeCG(StochasticCGIterationState<ScalarType,MV>& newstate)
  {
    // Check if there is any multivector to clone from.
    Teuchos::RCP<const MV> lhsMV = lp_->getCurrLHSVec();
    Teuchos::RCP<const MV> rhsMV = lp_->getCurrRHSVec();
    TEUCHOS_TEST_FOR_EXCEPTION((lhsMV==Teuchos::null && rhsMV==Teuchos::null),std::invalid_argument,
           "Belos::PseudoBlockStochasticCGIter::initialize(): Cannot initialize state storage!");
 
    // Get the multivector that is not null.
    Teuchos::RCP<const MV> tmp = ( (rhsMV!=Teuchos::null)? rhsMV: lhsMV );
 
    // Get the number of right-hand sides we're solving for now.
    int numRHS = MVT::GetNumberVecs(*tmp);
    numRHS_ = numRHS;
  
    // Initialize the state storage
    // If the subspace has not be initialized before or has changed sizes, generate it using the LHS or RHS from lp_.
    if (Teuchos::is_null(R_) || MVT::GetNumberVecs(*R_)!=numRHS_) {
      R_  = MVT::Clone( *tmp, numRHS_ );
      Z_  = MVT::Clone( *tmp, numRHS_ );
      P_  = MVT::Clone( *tmp, numRHS_ );
      AP_ = MVT::Clone( *tmp, numRHS_ );
      Y_  = MVT::Clone( *tmp, numRHS_ );
    }
 
    // Initialize the random vector container with zeros.
    randvec_.size( numRHS_ );
  
    // NOTE:  In StochasticCGIter R_, the initial residual, is required!!!  
    //
    std::string errstr("Belos::BlockPseudoStochasticCGIter::initialize(): Specified multivectors must have a consistent length and width.");
 
    if (!Teuchos::is_null(newstate.R)) {
 
      TEUCHOS_TEST_FOR_EXCEPTION( MVT::GetGlobalLength(*newstate.R) != MVT::GetGlobalLength(*R_),
                          std::invalid_argument, errstr );
      TEUCHOS_TEST_FOR_EXCEPTION( MVT::GetNumberVecs(*newstate.R) != numRHS_,
                          std::invalid_argument, errstr );
 
      // Copy basis vectors from newstate into V
      if (newstate.R != R_) {
        // copy over the initial residual (unpreconditioned).
  MVT::Assign( *newstate.R, *R_ );
      }
 
      // Compute initial direction vectors
      // Initially, they are set to the preconditioned residuals
      
      if ( lp_->getLeftPrec() != Teuchos::null ) {
        lp_->applyLeftPrec( *R_, *Z_ );
        if ( lp_->getRightPrec() != Teuchos::null ) {
          Teuchos::RCP<MV> tmp2 = MVT::Clone( *Z_, numRHS_ );
          lp_->applyRightPrec( *Z_, *tmp2 );
          Z_ = tmp2;
        }
      }
      else if ( lp_->getRightPrec() != Teuchos::null ) {
  lp_->applyRightPrec( *R_, *Z_ ); 
      } 
      else {
  Z_ = R_;
      }
      MVT::Assign( *Z_, *P_ );
    }
    else {
 
      TEUCHOS_TEST_FOR_EXCEPTION(Teuchos::is_null(newstate.R),std::invalid_argument,
                         "Belos::StochasticCGIter::initialize(): CGStateIterState does not have initial residual.");
    }
 
    // The solver is initialized
    initialized_ = true;
  }
 
 
  // Iterate until the status test informs us we should stop.
  template<class ScalarType, class MV, class OP, class DM>
  void PseudoBlockStochasticCGIter<ScalarType,MV,OP,DM>::iterate()
  {
    //
    // Allocate/initialize data structures
    //
    if (initialized_ == false) {
      initialize();
    }
 
    // Allocate memory for scalars.
    int i=0;
    std::vector<int> index(1);
    std::vector<ScalarType> rHz( numRHS_ ), rHz_old( numRHS_ ), pAp( numRHS_ ), beta( numRHS_ );
    Teuchos::RCP<DM> alpha = DMT::Create( numRHS_,numRHS_ );
    Teuchos::RCP<DM> zeta = DMT::Create( numRHS_,numRHS_ );
 
    // Create convenience variables for zero and one.
    const ScalarType one = Teuchos::ScalarTraits<ScalarType>::one();
    const MagnitudeType zero = Teuchos::ScalarTraits<MagnitudeType>::zero();
    
    // Get the current solution std::vector.
    Teuchos::RCP<MV> cur_soln_vec = lp_->getCurrLHSVec();
 
    // Compute first <r,z> a.k.a. rHz
    MVT::MvDot( *R_, *Z_, rHz );
 
    if ( assertPositiveDefiniteness_ )
        for (i=0; i<numRHS_; ++i)
            TEUCHOS_TEST_FOR_EXCEPTION( SCT::real(rHz[i]) < zero,
                                CGPositiveDefiniteFailure,
                                "Belos::PseudoBlockStochasticCGIter::iterate(): negative value for r^H*M*r encountered!" );
 
    // Iterate until the status test tells us to stop.
    //
    while (stest_->checkStatus(this) != Passed) {
      
      // Increment the iteration
      iter_++;
 
      // Multiply the current direction std::vector by A and store in AP_
      lp_->applyOp( *P_, *AP_ );
      
      // Compute alpha := <R_,Z_> / <P_,AP_>
      MVT::MvDot( *P_, *AP_, pAp );
 
      Teuchos::SerialDenseVector<int,ScalarType>& z = normal();
 
      for (i=0; i<numRHS_; ++i) {
        if ( assertPositiveDefiniteness_ )
            // Check that pAp[i] is a positive number!
            TEUCHOS_TEST_FOR_EXCEPTION( SCT::real(pAp[i]) <= zero,
                                CGPositiveDefiniteFailure,
                                "Belos::PseudoBlockStochasticCGIter::iterate(): non-positive value for p^H*A*p encountered!" );
 
        DMT::Value(*alpha,i,i) = rHz[i] / pAp[i];
 
  // Compute the scaling parameter for the stochastic vector
  DMT::Value(*zeta,i,i) = z[i] / Teuchos::ScalarTraits<ScalarType>::squareroot(pAp[i]);
      }
      DMT::SyncDeviceToHost( *alpha );
      DMT::SyncDeviceToHost( *zeta );
 
      //
      // Update the solution std::vector x := x + alpha * P_
      //
      MVT::MvTimesMatAddMv( one, *P_, *alpha, one, *cur_soln_vec );
      lp_->updateSolution();
 
      // Updates the stochastic vector y := y + zeta * P_
      MVT::MvTimesMatAddMv( one, *P_, *zeta, one, *Y_);
 
      //
      // Save the denominator of beta before residual is updated [ old <R_, Z_> ]
      //
      for (i=0; i<numRHS_; ++i) {
        rHz_old[i] = rHz[i];
      }
      //
      // Compute the new residual R_ := R_ - alpha * AP_
      //
      MVT::MvTimesMatAddMv( -one, *AP_, *alpha, one, *R_ );
      //
      // Compute beta := [ new <R_, Z_> ] / [ old <R_, Z_> ], 
      // and the new direction std::vector p.
      //
      if ( lp_->getLeftPrec() != Teuchos::null ) {
        lp_->applyLeftPrec( *R_, *Z_ );
        if ( lp_->getRightPrec() != Teuchos::null ) {
          Teuchos::RCP<MV> tmp = MVT::Clone( *Z_, numRHS_ );
          lp_->applyRightPrec( *Z_, *tmp );
          Z_ = tmp;
        }
      }
      else if ( lp_->getRightPrec() != Teuchos::null ) {
        lp_->applyRightPrec( *R_, *Z_ );
      } 
      else {
        Z_ = R_;
      }
      //
      MVT::MvDot( *R_, *Z_, rHz );
      if ( assertPositiveDefiniteness_ )
          for (i=0; i<numRHS_; ++i)
              TEUCHOS_TEST_FOR_EXCEPTION( SCT::real(rHz[i]) < zero,
                                  CGPositiveDefiniteFailure,
                                  "Belos::PseudoBlockStochasticCGIter::iterate(): negative value for r^H*M*r encountered!" );
      //
      // Update the search directions.
      for (i=0; i<numRHS_; ++i) {
        beta[i] = rHz[i] / rHz_old[i];
  index[0] = i;
  Teuchos::RCP<const MV> Z_i = MVT::CloneView( *Z_, index );
  Teuchos::RCP<MV> P_i = MVT::CloneViewNonConst( *P_, index );
        MVT::MvAddMv( one, *Z_i, beta[i], *P_i, *P_i );
      }
      //      
    } // end while (sTest_->checkStatus(this) != Passed)
  }
 
} // end Belos namespace
 
#endif /* BELOS_PSEUDO_BLOCK_STOCHASTIC_CG_ITER_HPP */