boost/histogram/algorithm/reduce.hpp
// Copyright 2018 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_ALGORITHM_REDUCE_HPP
#define BOOST_HISTOGRAM_ALGORITHM_REDUCE_HPP
#include <boost/assert.hpp>
#include <boost/histogram/detail/axes.hpp>
#include <boost/histogram/detail/meta.hpp>
#include <boost/histogram/fwd.hpp>
#include <boost/histogram/indexed.hpp>
#include <boost/histogram/unsafe_access.hpp>
#include <boost/throw_exception.hpp>
#include <cmath>
#include <limits>
#include <stdexcept>
#include <type_traits>
namespace boost {
namespace histogram {
namespace algorithm {
/**
Option type returned by the helper functions shrink_and_rebin(), shrink(), rebin().
*/
struct reduce_option {
#ifndef BOOST_HISTOGRAM_DOXYGEN_INVOKED
unsigned iaxis = 0;
double lower, upper;
unsigned merge = 0;
reduce_option() noexcept = default;
reduce_option(unsigned i, double l, double u, unsigned m)
: iaxis(i), lower(l), upper(u), merge(m) {
if (lower == upper)
BOOST_THROW_EXCEPTION(std::invalid_argument("lower != upper required"));
if (merge == 0) BOOST_THROW_EXCEPTION(std::invalid_argument("merge > 0 required"));
}
#endif
};
/**
Shrink and rebin option.
@param iaxis which axis to operate on.
@param lower lowest bound that should be kept.
@param upper highest bound that should be kept. If upper is inside bin interval, the
whole interval is removed.
@param merge how many adjacent bins to merge into one.
*/
inline auto shrink_and_rebin(unsigned iaxis, double lower, double upper, unsigned merge) {
return reduce_option{iaxis, lower, upper, merge};
}
/**
Shrink option.
@param iaxis which axis to operate on.
@param lower lowest bound that should be kept.
@param upper highest bound that should be kept. If upper is inside bin interval, the
whole interval is removed.
*/
inline auto shrink(unsigned iaxis, double lower, double upper) {
return reduce_option{iaxis, lower, upper, 1};
}
/**
Rebin option.
@param iaxis which axis to operate on.
@param merge how many adjacent bins to merge into one.
*/
inline auto rebin(unsigned iaxis, unsigned merge) {
return reduce_option{iaxis, std::numeric_limits<double>::quiet_NaN(),
std::numeric_limits<double>::quiet_NaN(), merge};
}
/**
Convenience overload for single axis.
@param lower lowest bound that should be kept.
@param upper highest bound that should be kept. If upper is inside bin interval, the
whole interval is removed.
@param merge how many adjacent bins to merge into one.
*/
inline auto shrink_and_rebin(double lower, double upper, unsigned merge) {
return shrink_and_rebin(0, lower, upper, merge);
}
/**
Convenience overload for single axis.
@param lower lowest bound that should be kept.
@param upper highest bound that should be kept. If upper is inside bin interval, the
whole interval is removed.
*/
inline auto shrink(double lower, double upper) { return shrink(0, lower, upper); }
/**
Convenience overload for single axis.
@param merge how many adjacent bins to merge into one.
*/
inline auto rebin(unsigned merge) { return rebin(0, merge); }
/**
Shrink and/or rebin axes of a histogram.
Returns the reduced copy of the histogram.
@param hist original histogram.
@param options iterable sequence of reduce_options, generated by shrink_and_rebin(),
shrink(), and rebin().
*/
#ifndef BOOST_HISTOGRAM_DOXYGEN_INVOKED
template <class Histogram, class Iterable, class = detail::requires_iterable<Iterable>>
#else
template <class Histogram, class Iterable>
#endif
decltype(auto) reduce(const Histogram& hist, const Iterable& options) {
const auto& old_axes = unsafe_access::axes(hist);
struct option_item : reduce_option {
int begin, end;
};
auto opts = detail::make_stack_buffer<option_item>(old_axes);
for (const auto& o : options) {
auto& oi = opts[o.iaxis];
if (oi.merge > 0) // did we already set the option for this axis?
BOOST_THROW_EXCEPTION(std::invalid_argument("indices must be unique"));
oi.lower = o.lower;
oi.upper = o.upper;
oi.merge = o.merge;
}
// make new axes container with default-constructed axis instances
auto axes = detail::make_default(old_axes);
detail::static_if<detail::is_tuple<decltype(axes)>>(
[](auto&, const auto&) {},
[](auto& axes, const auto& old_axes) {
axes.reserve(old_axes.size());
for (const auto& a : old_axes) axes.emplace_back(detail::make_default(a));
},
axes, old_axes);
// override default-constructed axis instances with modified instances
unsigned iaxis = 0;
hist.for_each_axis([&](const auto& a) {
using T = detail::remove_cvref_t<decltype(a)>;
auto& o = opts[iaxis];
o.begin = 0;
o.end = a.size();
if (o.merge > 0) { // option is set?
if (o.lower < o.upper) {
while (o.begin != o.end && a.value(o.begin) < o.lower) ++o.begin;
while (o.end != o.begin && a.value(o.end - 1) >= o.upper) --o.end;
} else if (o.lower > o.upper) {
// for inverted axis::regular
while (o.begin != o.end && a.value(o.begin) > o.lower) ++o.begin;
while (o.end != o.begin && a.value(o.end - 1) <= o.upper) --o.end;
}
o.end -= (o.end - o.begin) % o.merge;
auto a2 = T(a, o.begin, o.end, o.merge);
axis::get<T>(detail::axis_get(axes, iaxis)) = a2;
} else {
o.merge = 1;
axis::get<T>(detail::axis_get(axes, iaxis)) = a;
}
++iaxis;
});
auto storage = detail::make_default(unsafe_access::storage(hist));
auto result = Histogram(std::move(axes), std::move(storage));
auto idx = detail::make_stack_buffer<int>(unsafe_access::axes(result));
for (auto x : indexed(hist, coverage::all)) {
auto i = idx.begin();
auto o = opts.begin();
for (auto j : x.indices()) {
*i = (j - o->begin);
if (*i <= -1)
*i = -1;
else {
*i /= o->merge;
const int end = (o->end - o->begin) / o->merge;
if (*i > end) *i = end;
}
++i;
++o;
}
result.at(idx) += *x;
}
return result;
}
/**
Shrink and/or rebin axes of a histogram.
Returns the modified copy.
@param hist original histogram.
@param opt reduce option generated by shrink_and_rebin(), shrink(), and rebin().
@param opts more reduce_options.
*/
template <class Histogram, class... Ts>
decltype(auto) reduce(const Histogram& hist, const reduce_option& opt, Ts&&... opts) {
// this must be in one line, because any of the ts could be a temporary
return reduce(hist, std::initializer_list<reduce_option>{opt, opts...});
}
} // namespace algorithm
} // namespace histogram
} // namespace boost
#endif