diff options
Diffstat (limited to 'Eigen/src/Core/Ref.h')
| -rw-r--r-- | Eigen/src/Core/Ref.h | 141 |
1 files changed, 70 insertions, 71 deletions
diff --git a/Eigen/src/Core/Ref.h b/Eigen/src/Core/Ref.h index 61de5ed17..6e94181f3 100644 --- a/Eigen/src/Core/Ref.h +++ b/Eigen/src/Core/Ref.h @@ -12,76 +12,6 @@ namespace Eigen { -/** \class Ref - * \ingroup Core_Module - * - * \brief A matrix or vector expression mapping an existing expression - * - * \tparam PlainObjectType the equivalent matrix type of the mapped data - * \tparam MapOptions specifies the pointer alignment in bytes. It can be: \c #Aligned128, , \c #Aligned64, \c #Aligned32, \c #Aligned16, \c #Aligned8 or \c #Unaligned. - * The default is \c #Unaligned. - * \tparam StrideType optionally specifies strides. By default, Ref implies a contiguous storage along the inner dimension (inner stride==1), - * but accepts a variable outer stride (leading dimension). - * This can be overridden by specifying strides. - * The type passed here must be a specialization of the Stride template, see examples below. - * - * This class provides a way to write non-template functions taking Eigen objects as parameters while limiting the number of copies. - * A Ref<> object can represent either a const expression or a l-value: - * \code - * // in-out argument: - * void foo1(Ref<VectorXf> x); - * - * // read-only const argument: - * void foo2(const Ref<const VectorXf>& x); - * \endcode - * - * In the in-out case, the input argument must satisfy the constraints of the actual Ref<> type, otherwise a compilation issue will be triggered. - * By default, a Ref<VectorXf> can reference any dense vector expression of float having a contiguous memory layout. - * Likewise, a Ref<MatrixXf> can reference any column-major dense matrix expression of float whose column's elements are contiguously stored with - * the possibility to have a constant space in-between each column, i.e. the inner stride must be equal to 1, but the outer stride (or leading dimension) - * can be greater than the number of rows. - * - * In the const case, if the input expression does not match the above requirement, then it is evaluated into a temporary before being passed to the function. - * Here are some examples: - * \code - * MatrixXf A; - * VectorXf a; - * foo1(a.head()); // OK - * foo1(A.col()); // OK - * foo1(A.row()); // Compilation error because here innerstride!=1 - * foo2(A.row()); // Compilation error because A.row() is a 1xN object while foo2 is expecting a Nx1 object - * foo2(A.row().transpose()); // The row is copied into a contiguous temporary - * foo2(2*a); // The expression is evaluated into a temporary - * foo2(A.col().segment(2,4)); // No temporary - * \endcode - * - * The range of inputs that can be referenced without temporary can be enlarged using the last two template parameters. - * Here is an example accepting an innerstride!=1: - * \code - * // in-out argument: - * void foo3(Ref<VectorXf,0,InnerStride<> > x); - * foo3(A.row()); // OK - * \endcode - * The downside here is that the function foo3 might be significantly slower than foo1 because it won't be able to exploit vectorization, and will involve more - * expensive address computations even if the input is contiguously stored in memory. To overcome this issue, one might propose to overload internally calling a - * template function, e.g.: - * \code - * // in the .h: - * void foo(const Ref<MatrixXf>& A); - * void foo(const Ref<MatrixXf,0,Stride<> >& A); - * - * // in the .cpp: - * template<typename TypeOfA> void foo_impl(const TypeOfA& A) { - * ... // crazy code goes here - * } - * void foo(const Ref<MatrixXf>& A) { foo_impl(A); } - * void foo(const Ref<MatrixXf,0,Stride<> >& A) { foo_impl(A); } - * \endcode - * - * - * \sa PlainObjectBase::Map(), \ref TopicStorageOrders - */ - namespace internal { template<typename _PlainObjectType, int _Options, typename _StrideType> @@ -182,7 +112,75 @@ protected: StrideBase m_stride; }; - +/** \class Ref + * \ingroup Core_Module + * + * \brief A matrix or vector expression mapping an existing expression + * + * \tparam PlainObjectType the equivalent matrix type of the mapped data + * \tparam Options specifies the pointer alignment in bytes. It can be: \c #Aligned128, , \c #Aligned64, \c #Aligned32, \c #Aligned16, \c #Aligned8 or \c #Unaligned. + * The default is \c #Unaligned. + * \tparam StrideType optionally specifies strides. By default, Ref implies a contiguous storage along the inner dimension (inner stride==1), + * but accepts a variable outer stride (leading dimension). + * This can be overridden by specifying strides. + * The type passed here must be a specialization of the Stride template, see examples below. + * + * This class provides a way to write non-template functions taking Eigen objects as parameters while limiting the number of copies. + * A Ref<> object can represent either a const expression or a l-value: + * \code + * // in-out argument: + * void foo1(Ref<VectorXf> x); + * + * // read-only const argument: + * void foo2(const Ref<const VectorXf>& x); + * \endcode + * + * In the in-out case, the input argument must satisfy the constraints of the actual Ref<> type, otherwise a compilation issue will be triggered. + * By default, a Ref<VectorXf> can reference any dense vector expression of float having a contiguous memory layout. + * Likewise, a Ref<MatrixXf> can reference any column-major dense matrix expression of float whose column's elements are contiguously stored with + * the possibility to have a constant space in-between each column, i.e. the inner stride must be equal to 1, but the outer stride (or leading dimension) + * can be greater than the number of rows. + * + * In the const case, if the input expression does not match the above requirement, then it is evaluated into a temporary before being passed to the function. + * Here are some examples: + * \code + * MatrixXf A; + * VectorXf a; + * foo1(a.head()); // OK + * foo1(A.col()); // OK + * foo1(A.row()); // Compilation error because here innerstride!=1 + * foo2(A.row()); // Compilation error because A.row() is a 1xN object while foo2 is expecting a Nx1 object + * foo2(A.row().transpose()); // The row is copied into a contiguous temporary + * foo2(2*a); // The expression is evaluated into a temporary + * foo2(A.col().segment(2,4)); // No temporary + * \endcode + * + * The range of inputs that can be referenced without temporary can be enlarged using the last two template parameters. + * Here is an example accepting an innerstride!=1: + * \code + * // in-out argument: + * void foo3(Ref<VectorXf,0,InnerStride<> > x); + * foo3(A.row()); // OK + * \endcode + * The downside here is that the function foo3 might be significantly slower than foo1 because it won't be able to exploit vectorization, and will involve more + * expensive address computations even if the input is contiguously stored in memory. To overcome this issue, one might propose to overload internally calling a + * template function, e.g.: + * \code + * // in the .h: + * void foo(const Ref<MatrixXf>& A); + * void foo(const Ref<MatrixXf,0,Stride<> >& A); + * + * // in the .cpp: + * template<typename TypeOfA> void foo_impl(const TypeOfA& A) { + * ... // crazy code goes here + * } + * void foo(const Ref<MatrixXf>& A) { foo_impl(A); } + * void foo(const Ref<MatrixXf,0,Stride<> >& A) { foo_impl(A); } + * \endcode + * + * + * \sa PlainObjectBase::Map(), \ref TopicStorageOrders + */ template<typename PlainObjectType, int Options, typename StrideType> class Ref : public RefBase<Ref<PlainObjectType, Options, StrideType> > { @@ -209,6 +207,7 @@ template<typename PlainObjectType, int Options, typename StrideType> class Ref EIGEN_DEVICE_FUNC inline Ref(const DenseBase<Derived>& expr, typename internal::enable_if<bool(Traits::template match<Derived>::MatchAtCompileTime),Derived>::type* = 0) #else + /** Implicit constructor from any dense expression */ template<typename Derived> inline Ref(DenseBase<Derived>& expr) #endif |