/usr/include/deal.II/base/signaling_nan.h is in libdeal.ii-dev 8.4.2-2+b1.
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//
// Copyright (C) 2005 - 2016 by the deal.II authors
//
// This file is part of the deal.II library.
//
// The deal.II library is free software; you can use it, 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 2.1 of the License, or (at your option) any later version.
// The full text of the license can be found in the file LICENSE at
// the top level of the deal.II distribution.
//
// ---------------------------------------------------------------------
#ifndef dealii__signaling_nan_h
#define dealii__signaling_nan_h
#include <deal.II/base/config.h>
#include <deal.II/base/tensor.h>
#include <deal.II/base/symmetric_tensor.h>
#include <deal.II/base/derivative_form.h>
#include <limits>
DEAL_II_NAMESPACE_OPEN
namespace numbers
{
namespace internal
{
/**
* A namespace for the implementation of functions that create signaling
* NaN objects. This is where the Utilities::signaling_nan() function
* calls into.
*/
namespace SignalingNaN
{
/**
* A general template for classes that know how to initialize objects of
* type @p T with signaling NaNs to denote invalid values.
*
* The real implementation of this class happens in (partial)
* specializations for particular values of the template argument @p T.
*/
template <typename T>
struct NaNInitializer;
/**
* A specialization of the general NaNInitializer class that provides a
* function that returns a @p float value equal to the invalid signaling
* NaN.
*/
template <>
struct NaNInitializer<float>
{
static float invalid_element ()
{
return std::numeric_limits<float>::signaling_NaN();
}
};
/**
* A specialization of the general NaNInitializer class that provides a
* function that returns a @p double value equal to the invalid
* signaling NaN.
*/
template <>
struct NaNInitializer<double>
{
static double invalid_element ()
{
return std::numeric_limits<double>::signaling_NaN();
}
};
/**
* A specialization of the general NaNInitializer class that provides a
* function that returns a Tensor<1,dim> value whose components are
* invalid signaling NaN values.
*/
template <int dim, typename T>
struct NaNInitializer<Tensor<1,dim,T> >
{
static Tensor<1,dim,T> invalid_element ()
{
Tensor<1,dim,T> nan_tensor;
for (unsigned int i=0; i<dim; ++i)
nan_tensor[i] = NaNInitializer<T>::invalid_element();
return nan_tensor;
}
};
/**
* A specialization of the general NaNInitializer class that provides a
* function that returns a Tensor<rank,dim> value whose components are
* invalid signaling NaN values.
*/
template <int rank, int dim, typename T>
struct NaNInitializer<Tensor<rank,dim,T> >
{
static Tensor<rank,dim,T> invalid_element ()
{
Tensor<rank,dim,T> nan_tensor;
// recursively initialize sub-tensors with invalid elements
for (unsigned int i=0; i<dim; ++i)
nan_tensor[i] = NaNInitializer<Tensor<rank-1,dim,T> >::invalid_element();
return nan_tensor;
}
};
/**
* A specialization of the general NaNInitializer class that provides a
* function that returns a SymmetricTensor<rank,dim> value whose
* components are invalid signaling NaN values.
*/
template <int rank, int dim, typename T>
struct NaNInitializer<SymmetricTensor<rank,dim,T> >
{
static SymmetricTensor<rank,dim,T> invalid_element ()
{
// initialize symmetric tensors via the unrolled list of elements
T initializers[SymmetricTensor<rank,dim,T>::n_independent_components];
for (unsigned int i=0; i<SymmetricTensor<rank,dim,T>::n_independent_components; ++i)
initializers[i] = NaNInitializer<T>::invalid_element();
return SymmetricTensor<rank,dim,T>(initializers);
}
};
/**
* A specialization of the general NaNInitializer class that provides a
* function that returns a DerivativeForm<order,dim,spacedim> value
* whose components are invalid signaling NaN values.
*/
template <int order, int dim, int spacedim, typename T>
struct NaNInitializer<DerivativeForm<order,dim,spacedim,T> >
{
static DerivativeForm<order,dim,spacedim,T> invalid_element ()
{
DerivativeForm<order,dim,spacedim,T> form;
// recursively initialize sub-tensors with invalid elements
for (unsigned int i=0; i<spacedim; ++i)
form[i] = NaNInitializer<Tensor<order,dim,T> >::invalid_element();
return form;
}
};
}
}
/**
* Provide an object of type @p T filled with a signaling NaN that will
* cause an exception when used in a computation. The content of these
* objects is a "signaling NaN" ("NaN" stands for "not a number", and
* "signaling" implies that at least on platforms where this is supported,
* any arithmetic operation using them terminates the program). The purpose
* of such objects is to use them as markers for uninitialized objects and
* arrays that are required to be filled in other places, and to trigger an
* error when this later initialization does not happen before the first
* use.
*
* @tparam T The type of the returned invalid object. This type can either
* be a scalar, or of type Tensor, SymmetricTensor, or DerivativeForm. Other
* types may be supported if there is a corresponding specialization of the
* internal::SignalingNaN::NaNInitializer class for this type.
*
* @note Because the type @p T is not used as a function argument, the
* compiler cannot deduce it from the type of arguments. Consequently, you
* have to provide it explicitly. For example, the line
* @code
* Tensor<1,dim> tensor = Utilities::signaling_nan<Tensor<1,dim> >();
* @endcode
* initializes a tensor with invalid values.
*/
template <class T>
T
signaling_nan()
{
// dispatch to the classes in the internal namespace because there
// we can do partial specializations, which is not possible for
// template functions such as the current one
return internal::SignalingNaN::NaNInitializer<T>::invalid_element ();
}
}
DEAL_II_NAMESPACE_CLOSE
#endif
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