Eigen/src/Core/util/Constants.h

// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2008-2009 Gael Guennebaud <g.gael@free.fr>
// Copyright (C) 2007-2009 Benoit Jacob <jacob.benoit.1@gmail.com>
//
// Eigen is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 3 of the License, or (at your option) any later version.
//
// Alternatively, you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of
// the License, or (at your option) any later version.
//
// Eigen is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
// FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License or the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License and a copy of the GNU General Public License along with
// Eigen. If not, see <http://www.gnu.org/licenses/>.

#ifndef EIGEN_CONSTANTS_H
#define EIGEN_CONSTANTS_H

/** This value means that a quantity is not known at compile-time, and that instead the value is
  * stored in some runtime variable.
  *
  * Explanation for the choice of this value:
  * - It should be positive and larger than the number of entries in any reasonable fixed-size matrix.
  *   This allows to simplify many compile-time conditions throughout Eigen.
  * - It should be smaller than the sqrt of INT_MAX. Indeed, we often multiply a number of rows with a number
  *   of columns in order to compute a number of coefficients. Even if we guard that with an "if" checking whether
  *   the values are Dynamic, we still get a compiler warning "integer overflow". So the only way to get around
  *   it would be a meta-selector. Doing this everywhere would reduce code readability and lenghten compilation times.
  *   Also, disabling compiler warnings for integer overflow, sounds like a bad idea.
  * - It should be a prime number, because for example the old value 10000 led to bugs with 100x100 matrices.
  *
  * Changing the value of Dynamic breaks the ABI, as Dynamic is often used as a template parameter for Matrix.
  */
const int Dynamic = sizeof(int) >= 4 ? 33331 : 101;

/** This value means +Infinity; it is currently used only as the p parameter to MatrixBase::lpNorm<int>().
  * The value Infinity there means the L-infinity norm.
  */
const int Infinity = -1;

/** \defgroup flags flags
  * \ingroup Core_Module
  *
  * These are the possible bits which can be OR'ed to constitute the flags of a matrix or
  * expression.
  *
  * It is important to note that these flags are a purely compile-time notion. They are a compile-time property of
  * an expression type, implemented as enum's. They are not stored in memory at runtime, and they do not incur any
  * runtime overhead.
  *
  * \sa MatrixBase::Flags
  */

/** \ingroup flags
  *
  * for a matrix, this means that the storage order is row-major.
  * If this bit is not set, the storage order is column-major.
  * For an expression, this determines the storage order of
  * the matrix created by evaluation of that expression. */
const unsigned int RowMajorBit = 0x1;

/** \ingroup flags
  *
  * means the expression should be evaluated by the calling expression */
const unsigned int EvalBeforeNestingBit = 0x2;

/** \ingroup flags
  *
  * means the expression should be evaluated before any assignement */
const unsigned int EvalBeforeAssigningBit = 0x4;

/** \ingroup flags
  *
  * Short version: means the expression might be vectorized
  *
  * Long version: means that the coefficients can be handled by packets
  * and start at a memory location whose alignment meets the requirements
  * of the present CPU architecture for optimized packet access. In the fixed-size
  * case, there is the additional condition that the total size of the coefficients
  * array is a multiple of the packet size, so that it is possible to access all the
  * coefficients by packets. In the dynamic-size case, there is no such condition
  * on the total size, so it might not be possible to access the few last coeffs
  * by packets.
  *
  * \note This bit can be set regardless of whether vectorization is actually enabled.
  *       To check for actual vectorizability, see \a ActualPacketAccessBit.
  */
const unsigned int PacketAccessBit = 0x8;

#ifdef EIGEN_VECTORIZE
/** \ingroup flags
  *
  * If vectorization is enabled (EIGEN_VECTORIZE is defined) this constant
  * is set to the value \a PacketAccessBit.
  *
  * If vectorization is not enabled (EIGEN_VECTORIZE is not defined) this constant
  * is set to the value 0.
  */
const unsigned int ActualPacketAccessBit = PacketAccessBit;
#else
const unsigned int ActualPacketAccessBit = 0x0;
#endif

/** \ingroup flags
  *
  * Short version: means the expression can be seen as 1D vector.
  *
  * Long version: means that one can access the coefficients
  * of this expression by coeff(int), and coeffRef(int) in the case of a lvalue expression. These
  * index-based access methods are guaranteed
  * to not have to do any runtime computation of a (row, col)-pair from the index, so that it
  * is guaranteed that whenever it is available, index-based access is at least as fast as
  * (row,col)-based access. Expressions for which that isn't possible don't have the LinearAccessBit.
  *
  * If both PacketAccessBit and LinearAccessBit are set, then the
  * packets of this expression can be accessed by packet(int), and writePacket(int) in the case of a
  * lvalue expression.
  *
  * Typically, all vector expressions have the LinearAccessBit, but there is one exception:
  * Product expressions don't have it, because it would be troublesome for vectorization, even when the
  * Product is a vector expression. Thus, vector Product expressions allow index-based coefficient access but
  * not index-based packet access, so they don't have the LinearAccessBit.
  */
const unsigned int LinearAccessBit = 0x10;

/** \ingroup flags
  *
  * Means that the underlying array of coefficients can be directly accessed. This means two things.
  * First, references to the coefficients must be available through coeffRef(int, int). This rules out read-only
  * expressions whose coefficients are computed on demand by coeff(int, int). Second, the memory layout of the
  * array of coefficients must be exactly the natural one suggested by rows(), cols(), stride(), and the RowMajorBit.
  * This rules out expressions such as Diagonal, whose coefficients, though referencable, do not have
  * such a regular memory layout.
  */
const unsigned int DirectAccessBit = 0x20;

/** \ingroup flags
  *
  * means the first coefficient packet is guaranteed to be aligned */
const unsigned int AlignedBit = 0x40;


// list of flags that are inherited by default
const unsigned int HereditaryBits = RowMajorBit
                                  | EvalBeforeNestingBit
                                  | EvalBeforeAssigningBit;

// Possible values for the Mode parameter of triangularView()
enum {
  Lower=0x1, Upper=0x2, UnitDiag=0x4, ZeroDiag=0x8,
  UnitLower=UnitDiag|Lower, UnitUpper=UnitDiag|Upper,
  StrictlyLower=ZeroDiag|Lower, StrictlyUpper=ZeroDiag|Upper,
  SelfAdjoint=0x10};

enum { Unaligned=0, Aligned=1 };
enum { ConditionalJumpCost = 5 };
enum CornerType { TopLeft, TopRight, BottomLeft, BottomRight };
enum DirectionType { Vertical, Horizontal, BothDirections };
enum ProductEvaluationMode { NormalProduct, CacheFriendlyProduct };

enum {
  /** \internal Default traversal, no vectorization, no index-based access */
  DefaultTraversal,
  /** \internal No vectorization, use index-based access to have only one for loop instead of 2 nested loops */
  LinearTraversal,
  /** \internal Equivalent to a slice vectorization for fixed-size matrices having good alignment
    * and good size */
  InnerVectorizedTraversal,
  /** \internal Vectorization path using a single loop plus scalar loops for the
    * unaligned boundaries */
  LinearVectorizedTraversal,
  /** \internal Generic vectorization path using one vectorized loop per row/column with some
    * scalar loops to handle the unaligned boundaries */
  SliceVectorizedTraversal
};

enum {
  NoUnrolling,
  InnerUnrolling,
  CompleteUnrolling
};

enum {
  ColMajor = 0,
  RowMajor = 0x1,  // it is only a coincidence that this is equal to RowMajorBit -- don't rely on that
  /** \internal Align the matrix itself if it is vectorizable fixed-size */
  AutoAlign = 0,
  /** \internal Don't require alignment for the matrix itself (the array of coefficients, if dynamically allocated, may still be requested to be aligned) */ // FIXME --- clarify the situation
  DontAlign = 0x2
};

enum {
  OnTheLeft = 1,
  OnTheRight = 2
};

// options for SVD decomposition
enum {
  SkipU = 0x1,
  SkipV = 0x2,
  AtLeastAsManyRowsAsCols = 0x4,
  AtLeastAsManyColsAsRows = 0x8,
  Square = AtLeastAsManyRowsAsCols | AtLeastAsManyColsAsRows
};

/* the following could as well be written:
 *   enum NoChange_t { NoChange };
 * but it feels dangerous to disambiguate overloaded functions on enum/integer types.
 * If on some platform it is really impossible to get rid of "unused variable" warnings, then
 * we can always come back to that solution.
 */
struct NoChange_t {};
namespace {
  EIGEN_UNUSED NoChange_t NoChange;
}

struct Default_t {};
namespace {
  EIGEN_UNUSED Default_t Default;
}

enum {
  IsDense         = 0,
  IsSparse,
  NoDirectAccess  = 0,
  HasDirectAccess = DirectAccessBit
};

enum TransformTraits {
  Isometry      = 0x1,
  Affine        = 0x2,
  AffineCompact = 0x10 | Affine,
  Projective    = 0x20
};

namespace Architecture
{
  enum Type {
    Generic = 0x0,
    SSE = 0x1,
    AltiVec = 0x2,
#if defined EIGEN_VECTORIZE_SSE
    Target = SSE
#elif defined EIGEN_VECTORIZE_ALTIVEC
    Target = AltiVec
#else
    Target = Generic
#endif
  };
}

enum DenseStorageMatrix {};
enum DenseStorageArray {};

#endif // EIGEN_CONSTANTS_H