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#ifndef __RVL_LLA
#define __RVL_LLA

#include "local.hh"
#include "linalg.hh"
#include "functions.hh"

namespace RVL {

  /** LocalLinCombObject implements linear combination for
      LocalDataContainers: a call to operator() with
      LocalDataContainer arguments y and x in that order should
      implement y <- a*x + b*y, with whatever error checking is
      appropriate. Scalars a and b specified through a setScalar
      method, the only additional interface provided. Ordering is: a
      multiplies const input arg, b multiplies mutable input/output
      arg on rhs.
  */

  /** Interface to local function objects defining the basic ops of
      linear algebra in Hilbert space: linear combination, assignment
      to the zero vector, and inner product. Virtual base implementing
      the LinearAlgebraPackage interface at the local level,
      permitting any convenient definition of these objects.
  */

  template<class DataType, class Scalar = DataType>
  class LocalLinearAlgebraPackage: public LinearAlgebraPackage<Scalar> {

  public:
    LocalLinearAlgebraPackage() {}
    LocalLinearAlgebraPackage(const LocalLinearAlgebraPackage<Scalar, DataType> &) {}
    virtual ~LocalLinearAlgebraPackage() {}
  
    /** access to inner product */
    virtual BinaryLocalFunctionObjectScalarRedn<DataType,Scalar> & localinner() const = 0;
    /** inherited access to inner product */
    FunctionObjectScalarRedn<Scalar> & inner() const { return localinner(); }
    /** access to zero assignment */
    virtual UnaryLocalFunctionObject<DataType> & localzero() const = 0;
    /** inherited access to zero assignment */
    FunctionObject & zero() const { return localzero(); }
    // lincombobject deferred - must be specialized FO type

    /** Compare for compatibility with another LinearAlgebraPackage.
	Usual comparison basis - is the type the same? However
	"compatibility" can be defined more loosely when appropriate:
	the intended meaning is "produces the same results when
	applied to the same data". Returns zero if not compatible,
	nonzero otherwise. 
    */
    virtual bool compare( LinearAlgebraPackage<Scalar> const & lap) const = 0;

    /** report to exception */
    virtual void write(RVLException & e) const = 0;

    /** report to ostream */
    virtual ostream & write(ostream & str) const = 0;
  };

  /** This binary function object performs a linear combination
      u = a*v + b*u. Standard implementation, should be usable across
      a wide variety of data structures underlying vector algebra.     
  */
  template<class Scalar>
  class RVLLinCombObject: public BinaryLocalEvaluation<Scalar>, public LinCombObject<Scalar> {
  private:
    mutable Scalar a;
    mutable Scalar b;
  public:
    RVLLinCombObject(Scalar ain = ScalarFieldTraits<Scalar>::One(), 
		     Scalar bin = ScalarFieldTraits<Scalar>::One()): a(ain), b(bin) {}
    RVLLinCombObject(const RVLLinCombObject<Scalar> & lc ): a(lc.a), b(lc.b) {}
    ~RVLLinCombObject() {}

    /** runtime assignment of coefficients */
    void setScalar(Scalar ain, Scalar bin) { a=ain; b=bin; }

    /** u = a*v + b*u */
    using RVL::BinaryLocalEvaluation<Scalar>::operator();
    void operator() (LocalDataContainer<Scalar> & u, 
		     LocalDataContainer<Scalar> const & v) {
      size_t n = u.getSize();
      if (n > v.getSize()) {
	RVLException e; e<<"Error: RVLLinComb::operator()\n";
	e<<"operand 1 longer than operand 2 - not enough data\n";
	throw e;
      }

      // compiler should generate more efficient code for 
      // several special cases by avoiding explicit multiply

      Scalar * pu = u.getData();
      Scalar const * pv = v.getData();

      // special case u = v + b*u
      if (a == ScalarFieldTraits<Scalar>::One()) {
	// special case u = v + u;
	if (b == ScalarFieldTraits<Scalar>::One()) {
	  for (size_t i=0;i<n;i++) {
	    pu[i] = pv[i]+pu[i];
	  }
	}
	// special case u = v - u;
	else if (b == -ScalarFieldTraits<Scalar>::One()) {
	  for (size_t i=0;i<n;i++) {
	    pu[i] = pv[i]-pu[i];
	  }
	}
	// special case u = v;
	else if (b == ScalarFieldTraits<Scalar>::Zero()) {
	  RVLCopy<Scalar> cp;    
	  // use RVLCopy which uses memcpy for efficiency
	  cp(u,v);
	}
      
	else { 
	  for (size_t i=0;i<n;i++) {
	    pu[i] = pv[i]+b*pu[i];
	  }
	}
      }
      // special case u = -v + b*w;
      else if (a == -ScalarFieldTraits<Scalar>::One()) {
	// special case u = -v;
	if (b == ScalarFieldTraits<Scalar>::Zero()) {
	  for (size_t i=0;i<n;i++) {
	    pu[i] = -pv[i];
	  }
	}
	else {
	  for (size_t i=0;i<n;i++) {
	    pu[i] = -pv[i]+b*pu[i];
	  }
	}
      }
      // special case u = a*v;
      else if (b == ScalarFieldTraits<Scalar>::Zero()) {
	for (size_t i=0;i<n;i++) {
	  pu[i] = a*pv[i];
	}
      }
      // general case u = a*v + b*u
      else {
	for (size_t i=0;i<n;i++) {
	  pu[i] = a*pv[i]+b*pu[i];
	}
      }
    }

    string getName() const { string s = "RVLLinCombObject"; return s; }
  };

  /** The standard linear algebra package which should work for most Spaces.
      Combines an elementwise assignment to zero, standard dot product, and elementwise
      linear combination.
  */
  template<class Scalar>
  class RVLLinearAlgebraPackage: public LocalLinearAlgebraPackage<Scalar,Scalar> {

  private:

    mutable RVLAssignConst<Scalar> this_zero;
    mutable RVLL2innerProd<Scalar> this_inner;
    mutable RVLLinCombObject<Scalar> this_lco;

  public:

    RVLLinearAlgebraPackage(Scalar ipscale = ScalarFieldTraits<Scalar>::One())
      : this_zero(ScalarFieldTraits<Scalar>::Zero()), 
	this_inner(abs(ipscale)), this_lco() {}
    RVLLinearAlgebraPackage(const RVLLinearAlgebraPackage<Scalar> & p) 
      :this_zero(ScalarFieldTraits<Scalar>::Zero()),
       this_inner(p.this_inner.getScale()),this_lco() {}
    ~RVLLinearAlgebraPackage() {}

    BinaryLocalFunctionObjectScalarRedn<Scalar, Scalar> & localinner() const {
      return this_inner; 
    }
    UnaryLocalFunctionObject<Scalar> & localzero() const {
      return this_zero;
    }
    LinCombObject<Scalar> & linComb() const {
      return this_lco; 
    }

    virtual bool compare(LinearAlgebraPackage<Scalar> const & lap) const {
      RVLLinearAlgebraPackage<Scalar> const * laptr=NULL;
      laptr=dynamic_cast<RVLLinearAlgebraPackage<Scalar> const *>(&lap);
      if (laptr) return true;
      return false;
    }

    /** added to spparate instantiation from initialization */
    void setScale(Scalar newscale) { this_inner.setScale(newscale); }

    virtual void write(RVLException & e) const {
      e<<"RVLLinearAlgebraPackage\n";
    }

    virtual ostream & write(ostream & str) const {
      str<<"RVLLinearAlgebraPackage\n";
      return str;
    }
  };

}

#endif