Prebuilt Boost for Android
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.

352 lines
12 KiB

// Copyright 2015-2016 Hans Dembinski
//
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt
// or copy at http://www.boost.org/LICENSE_1_0.txt)
#ifndef BOOST_HISTOGRAM_INDEXED_HPP
#define BOOST_HISTOGRAM_INDEXED_HPP
#include <array>
#include <boost/config.hpp>
#include <boost/histogram/axis/traits.hpp>
#include <boost/histogram/detail/axes.hpp>
#include <boost/histogram/detail/iterator_adaptor.hpp>
#include <boost/histogram/detail/operators.hpp>
#include <boost/histogram/fwd.hpp>
#include <iterator>
#include <type_traits>
#include <utility>
namespace boost {
namespace histogram {
/** Coverage mode of the indexed range generator.
Defines options for the iteration strategy.
*/
enum class coverage {
inner, /*!< iterate over inner bins, exclude underflow and overflow */
all, /*!< iterate over all bins, including underflow and overflow */
};
/** Input iterator range over histogram bins with multi-dimensional index.
The iterator returned by begin() can only be incremented. begin() may only be called
once, calling it a second time returns the end() iterator. If several copies of the
input iterators exist, the other copies become invalid if one of them is incremented.
*/
template <class Histogram>
class BOOST_ATTRIBUTE_NODISCARD indexed_range {
private:
using histogram_type = Histogram;
static constexpr std::size_t buffer_size =
detail::buffer_size<typename std::remove_const_t<histogram_type>::axes_type>::value;
public:
using value_iterator = std::conditional_t<std::is_const<histogram_type>::value,
typename histogram_type::const_iterator,
typename histogram_type::iterator>;
using value_reference = typename std::iterator_traits<value_iterator>::reference;
using value_type = typename std::iterator_traits<value_iterator>::value_type;
class iterator;
using range_iterator = iterator; ///< deprecated
/** Lightweight view to access value and index of current cell.
The methods provide access to the current cell indices and bins. It acts like a
pointer to the cell value, and in a limited way also like a reference. To interoperate
with the algorithms of the standard library, the accessor is implicitly convertible to
a cell value. Assignments and comparisons are passed through to the cell. An accessor
is coupled to its parent indexed_range::iterator. Moving the parent iterator
forward also updates the linked accessor. Accessors are not copyable. They cannot be
stored in containers, but indexed_range::iterator can be stored.
*/
class BOOST_ATTRIBUTE_NODISCARD accessor : detail::mirrored<accessor, void> {
public:
/// Array-like view into the current multi-dimensional index.
class index_view {
using index_pointer = const typename iterator::index_data*;
public:
using const_reference = const axis::index_type&;
using reference = const_reference; ///< deprecated
/// implementation detail
class const_iterator
: public detail::iterator_adaptor<const_iterator, index_pointer,
const_reference> {
public:
const_reference operator*() const noexcept { return const_iterator::base()->idx; }
private:
explicit const_iterator(index_pointer i) noexcept
: const_iterator::iterator_adaptor_(i) {}
friend class index_view;
};
const_iterator begin() const noexcept { return const_iterator{begin_}; }
const_iterator end() const noexcept { return const_iterator{end_}; }
std::size_t size() const noexcept {
return static_cast<std::size_t>(end_ - begin_);
}
const_reference operator[](unsigned d) const noexcept { return begin_[d].idx; }
const_reference at(unsigned d) const { return begin_[d].idx; }
private:
/// implementation detail
index_view(index_pointer b, index_pointer e) : begin_(b), end_(e) {}
index_pointer begin_, end_;
friend class accessor;
};
// assignment is pass-through
accessor& operator=(const accessor& o) {
get() = o.get();
return *this;
}
// assignment is pass-through
template <class T>
accessor& operator=(const T& x) {
get() = x;
return *this;
}
/// Returns the cell reference.
value_reference get() const noexcept { return *(iter_.iter_); }
/// @copydoc get()
value_reference operator*() const noexcept { return get(); }
/// Access fields and methods of the cell object.
value_iterator operator->() const noexcept { return iter_.iter_; }
/// Access current index.
/// @param d axis dimension.
axis::index_type index(unsigned d = 0) const noexcept {
return iter_.indices_[d].idx;
}
/// Access indices as an iterable range.
index_view indices() const noexcept {
BOOST_ASSERT(iter_.indices_.hist_);
return {iter_.indices_.data(),
iter_.indices_.data() + iter_.indices_.hist_->rank()};
}
/// Access current bin.
/// @tparam N axis dimension.
template <unsigned N = 0>
decltype(auto) bin(std::integral_constant<unsigned, N> = {}) const {
BOOST_ASSERT(iter_.indices_.hist_);
return iter_.indices_.hist_->axis(std::integral_constant<unsigned, N>())
.bin(index(N));
}
/// Access current bin.
/// @param d axis dimension.
decltype(auto) bin(unsigned d) const {
BOOST_ASSERT(iter_.indices_.hist_);
return iter_.indices_.hist_->axis(d).bin(index(d));
}
/** Computes density in current cell.
The density is computed as the cell value divided by the product of bin widths. Axes
without bin widths, like axis::category, are treated as having unit bin with.
*/
double density() const {
BOOST_ASSERT(iter_.indices_.hist_);
double x = 1;
unsigned d = 0;
iter_.indices_.hist_->for_each_axis([&](const auto& a) {
const auto w = axis::traits::width_as<double>(a, this->index(d++));
x *= w ? w : 1;
});
return get() / x;
}
// forward all comparison operators to the value
bool operator<(const accessor& o) noexcept { return get() < o.get(); }
bool operator>(const accessor& o) noexcept { return get() > o.get(); }
bool operator==(const accessor& o) noexcept { return get() == o.get(); }
bool operator!=(const accessor& o) noexcept { return get() != o.get(); }
bool operator<=(const accessor& o) noexcept { return get() <= o.get(); }
bool operator>=(const accessor& o) noexcept { return get() >= o.get(); }
template <class U>
bool operator<(const U& o) const noexcept {
return get() < o;
}
template <class U>
bool operator>(const U& o) const noexcept {
return get() > o;
}
template <class U>
bool operator==(const U& o) const noexcept {
return get() == o;
}
template <class U>
bool operator!=(const U& o) const noexcept {
return get() != o;
}
template <class U>
bool operator<=(const U& o) const noexcept {
return get() <= o;
}
template <class U>
bool operator>=(const U& o) const noexcept {
return get() >= o;
}
operator value_type() const noexcept { return get(); }
private:
accessor(iterator& i) noexcept : iter_(i) {}
accessor(const accessor&) = default; // only callable by indexed_range::iterator
iterator& iter_;
friend class iterator;
};
/// implementation detail
class iterator {
public:
using value_type = typename indexed_range::value_type;
using reference = accessor;
private:
struct pointer_proxy {
reference* operator->() noexcept { return std::addressof(ref_); }
reference ref_;
};
public:
using pointer = pointer_proxy;
using difference_type = std::ptrdiff_t;
using iterator_category = std::forward_iterator_tag;
reference operator*() noexcept { return *this; }
pointer operator->() noexcept { return pointer_proxy{operator*()}; }
iterator& operator++() {
BOOST_ASSERT(indices_.hist_);
std::size_t stride = 1;
auto c = indices_.begin();
++c->idx;
++iter_;
while (c->idx == c->end && (c != (indices_.end() - 1))) {
c->idx = c->begin;
iter_ -= (c->end - c->begin) * stride;
stride *= c->extent;
++c;
++c->idx;
iter_ += stride;
}
return *this;
}
iterator operator++(int) {
auto prev = *this;
operator++();
return prev;
}
bool operator==(const iterator& x) const noexcept { return iter_ == x.iter_; }
bool operator!=(const iterator& x) const noexcept { return !operator==(x); }
private:
iterator(histogram_type* h) : iter_(h->begin()), indices_(h) {}
value_iterator iter_;
struct index_data {
axis::index_type idx, begin, end, extent;
};
struct indices_t : std::array<index_data, buffer_size> {
using base_type = std::array<index_data, buffer_size>;
indices_t(histogram_type* h) noexcept : hist_{h} {}
constexpr auto end() noexcept { return base_type::begin() + hist_->rank(); }
constexpr auto end() const noexcept { return base_type::begin() + hist_->rank(); }
histogram_type* hist_;
} indices_;
friend class indexed_range;
};
indexed_range(histogram_type& hist, coverage cov) : begin_(&hist), end_(&hist) {
std::size_t stride = 1;
auto ca = begin_.indices_.begin();
const auto clast = ca + begin_.indices_.hist_->rank() - 1;
begin_.indices_.hist_->for_each_axis(
[ca, clast, cov, &stride, this](const auto& a) mutable {
using opt = axis::traits::static_options<std::decay_t<decltype(a)>>;
constexpr int under = opt::test(axis::option::underflow);
constexpr int over = opt::test(axis::option::overflow);
const auto size = a.size();
ca->extent = size + under + over;
// -1 if underflow and cover all, else 0
ca->begin = cov == coverage::all ? -under : 0;
// size + 1 if overflow and cover all, else size
ca->end = cov == coverage::all ? size + over : size;
ca->idx = ca->begin;
begin_.iter_ += (ca->begin + under) * stride;
end_.iter_ += ((ca < clast ? ca->begin : ca->end) + under) * stride;
stride *= ca->extent;
++ca;
});
}
iterator begin() noexcept { return begin_; }
iterator end() noexcept { return end_; }
private:
iterator begin_, end_;
};
/** Generates an indexed range of <a
href="https://en.cppreference.com/w/cpp/named_req/ForwardIterator">forward iterators</a>
over the histogram cells.
Use this in a range-based for loop:
```
for (auto&& x : indexed(hist)) { ... }
```
This generates an optimized loop which is nearly always faster than a hand-written loop
over the histogram cells. The iterators dereference to an indexed_range::accessor, which
has methods to query the current indices and bins and acts like a pointer to the cell
value. The returned iterators are forward iterators. They can be stored in a container,
but may not be used after the life-time of the histogram ends.
@returns indexed_range
@param hist Reference to the histogram.
@param cov Iterate over all or only inner bins (optional, default: inner).
*/
template <class Histogram>
auto indexed(Histogram&& hist, coverage cov = coverage::inner) {
return indexed_range<std::remove_reference_t<Histogram>>{std::forward<Histogram>(hist),
cov};
}
} // namespace histogram
} // namespace boost
#endif