Fix performance issue with boost::range::join

include/powsybl/stdcxx/flattened.hpp

@@ -0,0 +1,119 @@
+/**
+ * Copyright (c) 2020, RTE (http://www.rte-france.com)
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#ifndef POWSYBL_STDCXX_FLATTENED_HPP
+#define POWSYBL_STDCXX_FLATTENED_HPP
+
+#include <boost/iterator_adaptors.hpp>
+#include <boost/range/iterator.hpp>
+#include <boost/range/iterator_range.hpp>
+
+namespace stdcxx {
+
+/**
+ * The FlatteningIterator is used to iterate over a range of ranges:
+ * - the OuterIterator is a forward iterator for the outer range
+ * - the InnerIterator is a forward iterator for the inner ranges.
+ *
+ * This iterator SHOULD not be used directly. Use the pipe operator instead.
+ */
+template <typename Iterator>
+class FlatteningIterator :
+    public boost::iterator_adaptor<
+        FlatteningIterator<Iterator>,
+        Iterator,
+        typename Iterator::value_type::iterator::value_type,
+        boost::forward_traversal_tag,
+        typename Iterator::value_type::iterator::value_type> {
+public:
+    using OuterIterator = Iterator;
+    using InnerIterator = typename Iterator::value_type::iterator;
+    using Value = typename Iterator::value_type::iterator::value_type;
+
+    using base = boost::iterator_adaptor<FlatteningIterator<Iterator>, Iterator, Value, boost::forward_traversal_tag, Value>;
+
+public:
+    FlatteningIterator() = default;
+
+    FlatteningIterator(Iterator it) :
+        base(it),
+        m_outer_end(it),
+        m_inner_begin(),
+        m_inner_end() {
+    }
+
+    FlatteningIterator(Iterator begin, Iterator end) :
+        base(begin),
+        m_outer_end(end) {
+
+        if (begin != end) {
+            m_inner_begin = (*begin).begin(),
+            m_inner_end = (*begin).end();
+            skipEmptyRanges();
+        }
+    }
+
+private:
+    void increment() {
+        if (this->base_reference() == m_outer_end) {
+            return;
+        }
+
+        ++m_inner_begin;
+        skipEmptyRanges();
+    }
+
+    Value dereference() const {
+        return *m_inner_begin;
+    }
+
+    void skipEmptyRanges() {
+        while ((this->base_reference() != m_outer_end) && (m_inner_begin == m_inner_end)) {
+            ++this->base_reference();
+            if (this->base_reference() != m_outer_end) {
+                m_inner_begin = (*this->base_reference()).begin();
+                m_inner_end = (*this->base_reference()).end();
+            }
+        }
+    }
+
+    friend class boost::iterator_core_access;
+
+private:
+    OuterIterator m_outer_end;
+    InnerIterator m_inner_begin;
+    InnerIterator m_inner_end;
+};
+
+struct FlattenForwarder {};
+
+namespace {
+
+const FlattenForwarder flattened;
+
+}  // namespace
+
+template <typename SinglePassRange>
+using FlattenRange = boost::iterator_range<FlatteningIterator<typename boost::range_iterator<SinglePassRange>::type>>;
+
+template <typename SinglePassRange>
+FlattenRange<SinglePassRange> operator|(SinglePassRange& range, FlattenForwarder) {
+    using Iterator = typename boost::range_iterator<SinglePassRange>::type;
+
+    return boost::make_iterator_range(FlatteningIterator<Iterator>(boost::begin(range), boost::end(range)), FlatteningIterator<Iterator>(boost::end(range)));
+}
+
+template <typename SinglePassRange>
+FlattenRange<SinglePassRange> operator|(const SinglePassRange& range, FlattenForwarder) {
+    using Iterator = typename boost::range_iterator<const SinglePassRange>::type;
+
+    return boost::make_iterator_range(FlatteningIterator<Iterator>(boost::begin(range), boost::end(range)), FlatteningIterator<Iterator>(boost::end(range)));
+}
+
+}  // namespace stdcxx
+
+#endif  // POWSYBL_STDCXX_FLATTENED_HPP

src/iidm/BusBreakerVoltageLevel.cpp

@@ -9,11 +9,12 @@
 
 #include <cassert>
 
-#include <boost/range/join.hpp>
+#include <boost/range/adaptor/transformed.hpp>
 
 #include <powsybl/iidm/Substation.hpp>
 #include <powsybl/iidm/Switch.hpp>
 #include <powsybl/iidm/ValidationUtils.hpp>
+#include <powsybl/stdcxx/flattened.hpp>
 
 #include "BusTerminal.hpp"
 
@@ -243,25 +244,19 @@ stdcxx::range<Switch> BusBreakerVoltageLevel::getSwitches() {
 }
 
 stdcxx::const_range<Terminal> BusBreakerVoltageLevel::getTerminals() const {
-    stdcxx::const_range<Terminal> terminals;
-    for (const auto& bus : m_graph.getVertexObjects()) {
-        if (bus) {
-            terminals = boost::range::join(terminals, bus.get().getTerminals());
-        }
-    }
+    const auto& mapper = [](const stdcxx::Reference<ConfiguredBus>& bus) {
+        return bus.get().getTerminals();
+    };
 
-    return terminals;
+    return m_graph.getVertexObjects() | boost::adaptors::transformed(mapper) | stdcxx::flattened;
 }
 
 stdcxx::range<Terminal> BusBreakerVoltageLevel::getTerminals() {
-    stdcxx::range<Terminal> terminals;
-    for (const auto& bus : m_graph.getVertexObjects()) {
-        if (bus) {
-            terminals = boost::range::join(terminals, bus.get().getTerminals());
-        }
-    }
+    const auto& mapper = [](const stdcxx::Reference<ConfiguredBus>& bus) {
+        return bus.get().getTerminals();
+    };
 
-    return terminals;
+    return m_graph.getVertexObjects() | boost::adaptors::transformed(mapper) | stdcxx::flattened;
 }
 
 const TopologyKind& BusBreakerVoltageLevel::getTopologyKind() const {

src/iidm/MergedBus.cpp

@@ -10,11 +10,12 @@
 #include <cassert>
 #include <cmath>
 
-#include <boost/range/join.hpp>
+#include <boost/range/adaptor/transformed.hpp>
 
 #include <powsybl/PowsyblException.hpp>
 #include <powsybl/iidm/Terminal.hpp>
 #include <powsybl/iidm/VoltageLevel.hpp>
+#include <powsybl/stdcxx/flattened.hpp>
 #include <powsybl/stdcxx/math.hpp>
 
 namespace powsybl {
@@ -76,25 +77,21 @@ unsigned long MergedBus::getConnectedTerminalCount() const {
 stdcxx::const_range<Terminal> MergedBus::getConnectedTerminals() const {
     checkValidity();
 
-    stdcxx::const_range<Terminal> range;
+    const auto& mapper = [](const std::reference_wrapper<ConfiguredBus>& bus) {
+        return bus.get().getConnectedTerminals();
+    };
 
-    for (const auto& bus : m_buses) {
-        range = boost::range::join(range, bus.get().getConnectedTerminals());
-    }
-
-    return range;
+    return m_buses | boost::adaptors::transformed(mapper) | stdcxx::flattened;
 }
 
 stdcxx::range<Terminal> MergedBus::getConnectedTerminals() {
     checkValidity();
 
-    stdcxx::range<Terminal> range;
-
-    for (const auto& bus : m_buses) {
-        range = boost::range::join(range, bus.get().getConnectedTerminals());
-    }
+    const auto& mapper = [](const std::reference_wrapper<ConfiguredBus>& bus) {
+        return bus.get().getConnectedTerminals();
+    };
 
-    return range;
+    return m_buses | boost::adaptors::transformed(mapper) | stdcxx::flattened;
 }
 
 stdcxx::CReference<Component> MergedBus::getSynchronousComponent() const {

src/iidm/NetworkViews.cpp

@@ -7,12 +7,13 @@
 
 #include <powsybl/iidm/NetworkViews.hpp>
 
-#include <boost/range/join.hpp>
+#include <boost/range/adaptor/transformed.hpp>
 
 #include <powsybl/iidm/Bus.hpp>
 #include <powsybl/iidm/Network.hpp>
 #include <powsybl/iidm/Switch.hpp>
 #include <powsybl/iidm/VoltageLevel.hpp>
+#include <powsybl/stdcxx/flattened.hpp>
 
 #include "BusBreakerVoltageLevelViews.hpp"
 
@@ -47,23 +48,19 @@ stdcxx::Reference<Bus> BusBreakerView::getBus(const std::string& id) {
 }
 
 stdcxx::const_range<Bus> BusBreakerView::getBuses() const {
-    stdcxx::const_range<Bus> range;
+    const auto& mapper = [](const VoltageLevel& voltageLevel) {
+        return voltageLevel.getBusBreakerView().getBuses();
+    };
 
-    for (const auto& vl : m_network.getVoltageLevels()) {
-        range = boost::range::join(range, vl.getBusBreakerView().getBuses());
-    }
-
-    return range;
+    return m_network.getVoltageLevels() | boost::adaptors::transformed(mapper) | stdcxx::flattened;
 }
 
 stdcxx::range<Bus> BusBreakerView::getBuses() {
-    stdcxx::range<Bus> range;
-
-    for (auto& vl : m_network.getVoltageLevels()) {
-        range = boost::range::join(range, vl.getBusBreakerView().getBuses());
-    }
+    const auto& mapper = [](const VoltageLevel& voltageLevel) {
+        return voltageLevel.getBusBreakerView().getBuses();
+    };
 
-    return range;
+    return m_network.getVoltageLevels() | boost::adaptors::transformed(mapper) | stdcxx::flattened;
 }
 
 unsigned long BusBreakerView::getSwitchCount() const {
@@ -77,23 +74,19 @@ unsigned long BusBreakerView::getSwitchCount() const {
 }
 
 stdcxx::const_range<Switch> BusBreakerView::getSwitches() const {
-    stdcxx::const_range<Switch> range;
-
-    for (const auto& vl : m_network.getVoltageLevels()) {
-        range = boost::range::join(range, vl.getBusBreakerView().getSwitches());
-    }
+    const auto& mapper = [](const VoltageLevel& voltageLevel) {
+        return voltageLevel.getBusBreakerView().getSwitches();
+    };
 
-    return range;
+    return m_network.getVoltageLevels() | boost::adaptors::transformed(mapper) | stdcxx::flattened;
 }
 
 stdcxx::range<Switch> BusBreakerView::getSwitches() {
-    stdcxx::range<Switch> range;
+    const auto& mapper = [](const VoltageLevel& voltageLevel) {
+        return voltageLevel.getBusBreakerView().getSwitches();
+    };
 
-    for (auto& vl : m_network.getVoltageLevels()) {
-        range = boost::range::join(range, vl.getBusBreakerView().getSwitches());
-    }
-
-    return range;
+    return m_network.getVoltageLevels() | boost::adaptors::transformed(mapper) | stdcxx::flattened;
 }
 
 BusView::BusView(Network& network) :
@@ -121,23 +114,19 @@ stdcxx::Reference<Bus> BusView::getBus(const std::string& id) {
 }
 
 stdcxx::const_range<Bus> BusView::getBuses() const {
-    stdcxx::const_range<Bus> range;
+    const auto& mapper = [](const VoltageLevel& voltageLevel) {
+        return voltageLevel.getBusView().getBuses();
+    };
 
-    for (const auto& vl : m_network.getVoltageLevels()) {
-        range = boost::range::join(range, vl.getBusView().getBuses());
-    }
-
-    return range;
+    return m_network.getVoltageLevels() | boost::adaptors::transformed(mapper) | stdcxx::flattened;
 }
 
 stdcxx::range<Bus> BusView::getBuses() {
-    stdcxx::range<Bus> range;
-
-    for (auto& vl : m_network.getVoltageLevels()) {
-        range = boost::range::join(range, vl.getBusView().getBuses());
-    }
+    const auto& mapper = [](const VoltageLevel& voltageLevel) {
+        return voltageLevel.getBusView().getBuses();
+    };
 
-    return range;
+    return m_network.getVoltageLevels() | boost::adaptors::transformed(mapper) | stdcxx::flattened;
 }
 
 stdcxx::const_range<Component> BusView::getConnectedComponents() const {