svectorbase.h

Go to the documentation of this file.

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/*                                                                           */
/*                  This file is part of the class library                   */
/*       SoPlex --- the Sequential object-oriented simPlex.                  */
/*                                                                           */
/*  Copyright (c) 1996-2023 Zuse Institute Berlin (ZIB)                      */
/*                                                                           */
/*  Licensed under the Apache License, Version 2.0 (the "License");          */
/*  you may not use this file except in compliance with the License.         */
/*  You may obtain a copy of the License at                                  */
/*                                                                           */
/*      http://www.apache.org/licenses/LICENSE-2.0                           */
/*                                                                           */
/*  Unless required by applicable law or agreed to in writing, software      */
/*  distributed under the License is distributed on an "AS IS" BASIS,        */
/*  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. */
/*  See the License for the specific language governing permissions and      */
/*  limitations under the License.                                           */
/*                                                                           */
/*  You should have received a copy of the Apache-2.0 license                */
/*  along with SoPlex; see the file LICENSE. If not email to soplex@zib.de.  */
/*                                                                           */
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/**@file  svectorbase.h
 * @brief Sparse vectors.
 */
#ifndef _SVECTORBASE_H_
#define _SVECTORBASE_H_

#include <iostream>
#include <assert.h>
#include <math.h>
#include <cmath>
#include "soplex/stablesum.h"

namespace soplex
{
template < class R > class VectorBase;
template < class R > class SSVectorBase;

/// Sparse vector nonzero element.
/** SVectorBase keeps its nonzeros in an array of Nonzero%s providing members for saving the index and value.
 */
template < class R >
class Nonzero
{
public:

   R val;        ///< Value of nonzero element.
   int idx;      ///< Index of nonzero element.

   template < class S >
   Nonzero<R>& operator=(const Nonzero<S>& vec)
   {
      // todo: is the cast really necessary? Previous code worked without a cast
      val = (R) vec.val;
      idx = vec.idx;
      return *this;
   }

   template < class S >
   Nonzero(const Nonzero<S>& vec)
      : val(vec.val)
      , idx(vec.idx)
   {
   }

   Nonzero()
      : val()
      , idx(0)
   {
   }
};



// specialized assignment operator
template <>
template < class S >
Nonzero<Real>& Nonzero<Real>::operator=(const Nonzero<S>& vec)
{
   val = Real(vec.val);
   idx = vec.idx;
   return *this;
}


/**@brief   Sparse vectors.
 * @ingroup Algebra
 *
 *  Class SVectorBase provides packed sparse vectors. Such are a sparse vectors, with a storage scheme that keeps all
 *  data in one contiguous block of memory.  This is best suited for using them for parallel computing on a distributed
 *  memory multiprocessor.
 *
 *  SVectorBase does not provide any memory management (this will be done by class DSVectorBase). This means, that the
 *  constructor of SVectorBase expects memory where to save the nonzeros. Further, adding nonzeros to an SVectorBase may
 *  fail if no more memory is available for saving them (see also DSVectorBase).
 *
 *  When nonzeros are added to an SVectorBase, they are appended to the set of nonzeros, i.e., they recieve numbers
 *  size(), size()+1 ... . An SVectorBase can hold atmost max() nonzeros, where max() is given in the constructor.  When
 *  removing nonzeros, the remaining nonzeros are renumbered. However, only the numbers greater than the number of the
 *  first removed nonzero are affected.
 *
 *  The following mathematical operations are provided by class SVectorBase (SVectorBase \p a, \p b, \p c; R \p x):
 *
 *  <TABLE>
 *  <TR><TD>Operation</TD><TD>Description   </TD><TD></TD>&nbsp;</TR>
 *  <TR><TD>\c -=    </TD><TD>subtraction   </TD><TD>\c a \c -= \c b </TD></TR>
 *  <TR><TD>\c +=    </TD><TD>addition      </TD><TD>\c a \c += \c b </TD></TR>
 *  <TR><TD>\c *     </TD><TD>skalar product</TD>
 *      <TD>\c x = \c a \c * \c b </TD></TR>
 *  <TR><TD>\c *=    </TD><TD>scaling       </TD><TD>\c a \c *= \c x </TD></TR>
 *  <TR><TD>maxAbs() </TD><TD>infinity norm </TD>
 *      <TD>\c a.maxAbs() == \f$\|a\|_{\infty}\f$ </TD></TR>
 *  <TR><TD>length() </TD><TD>eucledian norm</TD>
 *      <TD>\c a.length() == \f$\sqrt{a^2}\f$ </TD></TR>
 *  <TR><TD>length2()</TD><TD>square norm   </TD>
 *      <TD>\c a.length2() == \f$a^2\f$ </TD></TR>
 *  </TABLE>
 *
 *  Operators \c += and \c -= should be used with caution, since no efficient implementation is available. One should
 *  think of assigning the left handside vector to a dense VectorBase first and perform the addition on it. The same
 *  applies to the scalar product \c *.
 *
 *  There are two numberings of the nonzeros of an SVectorBase. First, an SVectorBase is supposed to act like a linear
 *  algebra VectorBase. An \em index refers to this view of an SVectorBase: operator[]() is provided which returns the
 *  value at the given index of the vector, i.e., 0 for all indices which are not in the set of nonzeros.  The other view
 *  of SVectorBase%s is that of a set of nonzeros. The nonzeros are numbered from 0 to size()-1.  The methods index(int
 *  n) and value(int n) allow to access the index and value of the \p n 'th nonzero.  \p n is referred to as the \em
 *  number of a nonzero.
 *
 *  @todo SVectorBase should get a new implementation.  There maybe a lot of memory lost due to padding the Nonzero
 *        structure. A better idea seems to be class SVectorBase { int size; int used; int* idx; R* val; }; which for
 *        several reasons could be faster or slower.  If SVectorBase is changed, also DSVectorBase and SVSet have to be
 *        modified.
 */
template < class R >
class SVectorBase
{
   template < class S > friend class SVectorBase;

private:

   // ------------------------------------------------------------------------------------------------------------------
   /**@name Data */
   ///@{

   Nonzero<R>* m_elem;
   int memsize;
   int memused;

   ///@}

public:

   typedef Nonzero<R> Element;

   // ------------------------------------------------------------------------------------------------------------------
   /**@name Access */
   ///@{

   /// Number of used indices.
   int size() const
   {
      assert(m_elem != 0 || memused == 0);
      return memused;
   }

   /// Maximal number of indices.
   int max() const
   {
      assert(m_elem != 0 || memused == 0);
      return memsize;
   }

   /// Dimension of the vector defined as maximal index + 1
   int dim() const
   {
      const Nonzero<R>* e = m_elem;
      int d = -1;
      int n = size();

      while(n--)
      {
         d = (d > e->idx) ? d : e->idx;
         e++;
      }

      return d + 1;
   }

   /// Position of index \p i.
   /** @return Finds the position of the first index \p i in the index set. If no such index \p i is found,
    *          -1 is returned. Otherwise, index(pos(i)) == i holds.
    */
   int pos(int i) const
   {
      if(m_elem != 0)
      {
         int n = size();

         for(int p = 0; p < n; ++p)
         {
            if(m_elem[p].idx == i)
            {
               assert(index(p) == i);
               return p;
            }
         }
      }

      return -1;
   }

   /// Value to index \p i.
   R operator[](int i) const
   {
      int n = pos(i);

      if(n >= 0)
         return m_elem[n].val;

      return 0;
   }

   /// Reference to the \p n 'th nonzero element.
   Nonzero<R>& element(int n)
   {
      assert(n >= 0);
      assert(n < max());

      return m_elem[n];
   }

   /// The \p n 'th nonzero element.
   const Nonzero<R>& element(int n) const
   {
      assert(n >= 0);
      assert(n < size());

      return m_elem[n];
   }

   /// Reference to index of \p n 'th nonzero.
   int& index(int n)
   {
      assert(n >= 0);
      assert(n < size());

      return m_elem[n].idx;
   }

   /// Index of \p n 'th nonzero.
   int index(int n) const
   {
      assert(n >= 0);
      assert(n < size());

      return m_elem[n].idx;
   }

   /// Reference to value of \p n 'th nonzero.
   R& value(int n)
   {
      assert(n >= 0);
      assert(n < size());

      return m_elem[n].val;
   }

   /// Value of \p n 'th nonzero.
   const R& value(int n) const
   {
      assert(n >= 0);
      assert(n < size());

      return m_elem[n].val;
   }

   /// Append one nonzero \p (i,v).
   void add(int i, const R& v)
   {
      assert(m_elem != 0);
      assert(size() < max());

      if(v != 0.0)
      {
         int n = size();

         m_elem[n].idx = i;
         m_elem[n].val = v;
         set_size(n + 1);

         assert(size() <= max());
      }
   }

   /// Append one uninitialized nonzero.
   void add(int i)
   {
      assert(m_elem != 0);
      assert(size() < max());

      int n = size();

      m_elem[n].idx = i;
      set_size(n + 1);

      assert(size() <= max());
   }

   /// Append nonzeros of \p sv.
   void add(const SVectorBase& sv)
   {
      add(sv.size(), sv.m_elem);
   }

   /// Append \p n nonzeros.
   void add(int n, const int i[], const R v[])
   {
      assert(n + size() <= max());

      if(n <= 0)
         return;

      int newnnz = 0;

      Nonzero<R>* e = m_elem + size();

      while(n--)
      {
         if(*v != 0.0)
         {
            assert(e != nullptr);
            e->idx = *i;
            e->val = *v;
            e++;
            ++newnnz;
         }

         i++;
         v++;
      }

      set_size(size() + newnnz);
   }

   /// Append \p n nonzeros.
   template < class S >
   void add(int n, const int i[], const S v[])
   {
      assert(n + size() <= max());

      if(n <= 0)
         return;

      int newnnz = 0;

      Nonzero<R>* e = m_elem + size();

      while(n--)
      {
         if(*v != R(0.0))
         {
            e->idx = *i;
            e->val = *v;
            e++;
            ++newnnz;
         }

         i++;
         v++;
      }

      set_size(size() + newnnz);
   }

   /// Append \p n nonzeros.
   void add(int n, const Nonzero<R> e[])
   {
      assert(n + size() <= max());

      if(n <= 0)
         return;

      int newnnz = 0;

      Nonzero<R>* ee = m_elem + size();

      while(n--)
      {
         if(e->val != 0.0)
         {
            *ee++ = *e;
            ++newnnz;
         }

         e++;
      }

      set_size(size() + newnnz);
   }

   /// Remove nonzeros \p n thru \p m.
   void remove(int n, int m)
   {
      assert(n <= m);
      assert(m < size());
      assert(n >= 0);

      ++m;

      int cpy = m - n;
      cpy = (size() - m >= cpy) ? cpy : size() - m;

      Nonzero<R>* e = &m_elem[size() - 1];
      Nonzero<R>* r = &m_elem[n];

      set_size(size() - cpy);

      do
      {
         *r++ = *e--;
      }
      while(--cpy);
   }

   /// Remove \p n 'th nonzero.
   void remove(int n)
   {
      assert(n >= 0);
      assert(n < size());

      int newsize = size() - 1;
      set_size(newsize);

      if(n < newsize)
         m_elem[n] = m_elem[newsize];
   }

   /// Remove all indices.
   void clear()
   {
      set_size(0);
   }

   /// Sort nonzeros to increasing indices.
   void sort()
   {
      if(m_elem != 0)
      {
         Nonzero<R> dummy;
         Nonzero<R>* w;
         Nonzero<R>* l;
         Nonzero<R>* s = &(m_elem[0]);
         Nonzero<R>* e = s + size();

         for(l = s, w = s + 1; w < e; l = w, ++w)
         {
            if(l->idx > w->idx)
            {
               dummy = *w;

               do
               {
                  l[1] = *l;

                  if(l-- == s)
                     break;
               }
               while(l->idx > dummy.idx);

               l[1] = dummy;
            }
         }
      }
   }

   ///@}

   // ------------------------------------------------------------------------------------------------------------------
   /**@name Arithmetic operations */
   ///@{

   /// Maximum absolute value, i.e., infinity norm.
   R maxAbs() const
   {
      R maxi = 0;

      for(int i = size() - 1; i >= 0; --i)
      {
         if(spxAbs(m_elem[i].val) > maxi)
            maxi = spxAbs(m_elem[i].val);
      }

      assert(maxi >= 0);

      return maxi;
   }

   /// Minimum absolute value.
   R minAbs() const
   {
      R mini = R(infinity);

      for(int i = size() - 1; i >= 0; --i)
      {
         if(spxAbs(m_elem[i].val) < mini)
            mini = spxAbs(m_elem[i].val);
      }

      assert(mini >= 0);

      return mini;
   }

   /// Floating point approximation of euclidian norm (without any approximation guarantee).
   R length() const
   {
      return std::sqrt(R(length2()));
   }

   /// Squared norm.
   R length2() const
   {
      R x = 0;
      int n = size();
      const Nonzero<R>* e = m_elem;

      while(n--)
      {
         x += e->val * e->val;
         e++;
      }

      return x;
   }

   /// Scaling.
   SVectorBase<R>& operator*=(const R& x)
   {
      int n = size();
      Nonzero<R>* e = m_elem;

      assert(x != 0);

      while(n--)
      {
         e->val *= x;
         e++;
      }

      return *this;
   }

   /// Inner product.
   R operator*(const VectorBase<R>& w) const;

   /// inner product for sparse vectors
   template < class S >
   R operator*(const SVectorBase<S>& w) const
   {
      StableSum<R> x;
      int n = size();
      int m = w.size();

      if(n == 0 || m == 0)
         return x;

      int i = 0;
      int j = 0;
      Element* e = m_elem;
      typename SVectorBase<S>::Element wj = w.element(j);

      while(true)
      {
         if(e->idx == wj.idx)
         {
            x += e->val * wj.val;
            i++;
            j++;

            if(i == n || j == m)
               break;

            e++;
            wj = w.element(j);
         }
         else if(e->idx < wj.idx)
         {
            i++;

            if(i == n)
               break;

            e++;
         }
         else
         {
            j++;

            if(j == m)
               break;

            wj = w.element(j);
         }
      }

      return x;
   }

   ///@}

   // ------------------------------------------------------------------------------------------------------------------
   /**@name Constructions, destruction, and assignment */
   ///@{

   /// Default constructor.
   /** The constructor expects one memory block where to store the nonzero elements. This must be passed to the
    *  constructor, where the \em number of Nonzero%s needs that fit into the memory must be given and a pointer to the
    *  beginning of the memory block. Once this memory has been passed, it shall not be modified until the SVectorBase
    *  is no longer used.
    */
   explicit SVectorBase(int n = 0, Nonzero<R>* p_mem = 0)
   {
      setMem(n, p_mem);
   }

   SVectorBase(const SVectorBase<R>& sv) = default;

   /// Assignment operator.
   template < class S >
   SVectorBase<R>& operator=(const VectorBase<S>& vec);

   /// Assignment operator.
   SVectorBase<R>& operator=(const SVectorBase<R>& sv)
   {
      if(this != &sv)
      {
         assert(max() >= sv.size());

         int i = sv.size();
         int nnz = 0;
         Nonzero<R>* e = m_elem;
         const Nonzero<R>* s = sv.m_elem;

         while(i--)
         {
            assert(e != 0);

            if(s->val != 0.0)
            {
               *e++ = *s;
               ++nnz;
            }

            ++s;
         }

         set_size(nnz);
      }

      return *this;
   }

   /// move assignement operator.
   SVectorBase<R>& operator=(const SVectorBase<R>&& sv)
   {
      if(this != &sv)
      {
         this->m_elem = sv.m_elem;
         this->memsize = sv.memsize;
         this->memused = sv.memused;
      }

      return *this;
   }

   /// Assignment operator.
   template < class S >
   SVectorBase<R>& operator=(const SVectorBase<S>& sv)
   {
      if(this != (const SVectorBase<R>*)(&sv))
      {
         assert(max() >= sv.size());

         int i = sv.size();
         int nnz = 0;
         Nonzero<R>* e = m_elem;
         const Nonzero<S>* s = sv.m_elem;

         while(i--)
         {
            assert(e != 0);

            if(s->val != 0.0)
            {
               *e++ = *s;
               ++nnz;
            }

            ++s;
         }

         set_size(nnz);
      }

      return *this;
   }

   /// scale and assign
   SVectorBase<Real>& scaleAssign(int scaleExp, const SVectorBase<Real>& sv)
   {
      if(this != &sv)
      {
         assert(max() >= sv.size());

         for(int i = 0; i < sv.size(); ++i)
         {
            m_elem[i].val = spxLdexp(sv.value(i), scaleExp);
            m_elem[i].idx = sv.index(i);
         }

         assert(isConsistent());
      }

      return *this;
   }

   /// scale and assign
   SVectorBase<Real>& scaleAssign(const int* scaleExp, const SVectorBase<Real>& sv,
                                  bool negateExp = false)
   {
      if(this != &sv)
      {
         assert(max() >= sv.size());

         if(negateExp)
         {
            for(int i = 0; i < sv.size(); ++i)
            {
               m_elem[i].val = spxLdexp(sv.value(i), -scaleExp[sv.index(i)]);
               m_elem[i].idx = sv.index(i);
            }
         }
         else
         {
            for(int i = 0; i < sv.size(); ++i)
            {
               m_elem[i].val = spxLdexp(sv.value(i), scaleExp[sv.index(i)]);
               m_elem[i].idx = sv.index(i);
            }
         }

         assert(isConsistent());
      }

      return *this;
   }


   /// Assignment operator.
   template < class S >
   SVectorBase<R>& assignArray(const S* rowValues, const int* rowIndices, int rowSize)
   {
      assert(max() >= rowSize);

      int i;

      for(i = 0; i < rowSize && i < max(); i++)
      {
         m_elem[i].val = rowValues[i];
         m_elem[i].idx = rowIndices[i];
      }

      set_size(i);

      return *this;
   }

   /// Assignment operator.
   template < class S >
   SVectorBase<R>& operator=(const SSVectorBase<S>& sv);

   ///@}

   // ------------------------------------------------------------------------------------------------------------------
   /**@name Memory */
   ///@{

   /// get pointer to internal memory.
   Nonzero<R>* mem() const
   {
      return m_elem;
   }

   /// Set size of the vector.
   void set_size(int s)
   {
      assert(m_elem != 0 || s == 0);
      memused = s;
   }

   /// Set the maximum number of nonzeros in the vector.
   void set_max(int m)
   {
      assert(m_elem != 0 || m == 0);
      memsize = m;
   }

   /// Set the memory area where the nonzeros will be stored.
   void setMem(int n, Nonzero<R>* elmem)
   {
      assert(n >= 0);
      assert(n == 0 || elmem != 0);

      m_elem = elmem;
      set_size(0);
      set_max(n);
   }

   ///@}

   // ------------------------------------------------------------------------------------------------------------------
   /**@name Utilities */
   ///@{

   /// Consistency check.
   bool isConsistent() const
   {
#ifdef ENABLE_CONSISTENCY_CHECKS

      if(m_elem != 0)
      {
         const int my_size = size();
         const int my_max = max();

         if(my_size < 0 || my_max < 0 || my_size > my_max)
            return SPX_MSG_INCONSISTENT("SVectorBase");

         for(int i = 1; i < my_size; ++i)
         {
            for(int j = 0; j < i; ++j)
            {
               // allow trailing zeros
               if(m_elem[i].idx == m_elem[j].idx && m_elem[i].val != 0)
                  return SPX_MSG_INCONSISTENT("SVectorBase");
            }
         }
      }

#endif

      return true;
   }

   ///@}
};



/// specialization for inner product for sparse vectors
template <>
template < class S >
Real SVectorBase<Real>::operator*(const SVectorBase<S>& w) const
{
   StableSum<Real> x;
   int n = size();
   int m = w.size();

   if(n == 0 || m == 0)
      return Real(0);

   int i = 0;
   int j = 0;
   SVectorBase<Real>::Element* e = m_elem;
   typename SVectorBase<S>::Element wj = w.element(j);

   while(true)
   {
      if(e->idx == wj.idx)
      {
         x += e->val * Real(wj.val);
         i++;
         j++;

         if(i == n || j == m)
            break;

         e++;
         wj = w.element(j);
      }
      else if(e->idx < wj.idx)
      {
         i++;

         if(i == n)
            break;

         e++;
      }
      else
      {
         j++;

         if(j == m)
            break;

         wj = w.element(j);
      }
   }

   return x;
}

} // namespace soplex
#endif // _SVECTORBASE_H_