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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include <cstddef>
#include <algorithm>
#include <vespa/vespalib/util/small_vector.h>
// Model how boolean result decisions flow through intermediate nodes
// of different types based on relative estimates for sub-expressions
namespace search::queryeval {
namespace flow {
// the default adapter expects the shape of std::unique_ptr<Blueprint>
// with respect to estimate, cost and (coming soon) strict_cost.
struct DefaultAdapter {
double estimate(const auto &child) const noexcept { return child->estimate(); }
double cost(const auto &child) const noexcept { return child->cost(); }
// Estimate the per-document cost of strict evaluation of this
// child. This will typically be something like (estimate() *
// cost()) for leafs with posting lists. OR will aggregate strict
// cost by calculating the minimal OR flow of strict child
// costs. AND will aggregate strict cost by calculating the
// minimal AND flow where the cost of the first child is
// substituted by its strict cost. This value is currently not
// available in Blueprints.
double strict_cost(const auto &child) const noexcept { return child->cost(); }
};
template <typename ADAPTER, typename T>
struct IndirectAdapter {
const T &data;
[[no_unique_address]] ADAPTER adapter;
IndirectAdapter(ADAPTER adapter_in, const T &data_in) noexcept
: data(data_in), adapter(adapter_in) {}
double estimate(size_t child) const noexcept { return adapter.estimate(data[child]); }
double cost(size_t child) const noexcept { return adapter.cost(data[child]); }
double strict_cost(size_t child) const noexcept { return adapter.strict_cost(data[child]); }
};
auto make_index(const auto &children) {
vespalib::SmallVector<uint32_t> index(children.size());
for (size_t i = 0; i < index.size(); ++i) {
index[i] = i;
}
return index;
}
template <typename ADAPTER>
struct MinAndCost {
// sort children to minimize total cost of AND flow
[[no_unique_address]] ADAPTER adapter;
MinAndCost(ADAPTER adapter_in) noexcept : adapter(adapter_in) {}
bool operator () (const auto &a, const auto &b) const noexcept {
return (1.0 - adapter.estimate(a)) * adapter.cost(b) > (1.0 - adapter.estimate(b)) * adapter.cost(a);
}
};
template <typename ADAPTER>
struct MinOrCost {
// sort children to minimize total cost of OR flow
[[no_unique_address]] ADAPTER adapter;
MinOrCost(ADAPTER adapter_in) noexcept : adapter(adapter_in) {}
bool operator () (const auto &a, const auto &b) const noexcept {
return adapter.estimate(a) * adapter.cost(b) > adapter.estimate(b) * adapter.cost(a);
}
};
template <typename ADAPTER>
struct MinOrStrictCost {
// sort children to minimize total cost of strict OR flow
[[no_unique_address]] ADAPTER adapter;
MinOrStrictCost(ADAPTER adapter_in) noexcept : adapter(adapter_in) {}
bool operator () (const auto &a, const auto &b) const noexcept {
return adapter.estimate(a) * adapter.strict_cost(b) > adapter.estimate(b) * adapter.strict_cost(a);
}
};
template <typename ADAPTER, typename T, typename F>
double estimate_of(ADAPTER adapter, const T &children, F flow) {
for (const auto &child: children) {
flow.add(adapter.estimate(child));
}
return flow.estimate();
}
template <template <typename> typename ORDER, typename ADAPTER, typename T>
void sort(ADAPTER adapter, T &children) {
std::sort(children.begin(), children.end(), ORDER(adapter));
}
template <template <typename> typename ORDER, typename ADAPTER, typename T>
void sort_partial(ADAPTER adapter, T &children, size_t offset) {
if (children.size() > offset) {
std::sort(children.begin() + offset, children.end(), ORDER(adapter));
}
}
template <typename ADAPTER, typename T, typename F>
double ordered_cost_of(ADAPTER adapter, const T &children, F flow) {
double cost = 0.0;
for (const auto &child: children) {
double child_cost = flow.strict() ? adapter.strict_cost(child) : adapter.cost(child);
cost += flow.flow() * child_cost;
flow.add(adapter.estimate(child));
}
return cost;
}
template <typename ADAPTER, typename T>
size_t select_strict_and_child(ADAPTER adapter, const T &children) {
size_t idx = 0;
double cost = 0.0;
size_t best_idx = 0;
double best_diff = 0.0;
double est = 1.0;
for (const auto &child: children) {
double child_cost = est * adapter.cost(child);
double child_strict_cost = adapter.strict_cost(child);
double child_est = adapter.estimate(child);
if (idx == 0) {
best_diff = child_strict_cost - child_cost;
} else {
double my_diff = (child_strict_cost + child_est * cost) - (cost + child_cost);
if (my_diff < best_diff) {
best_diff = my_diff;
best_idx = idx;
}
}
cost += child_cost;
est *= child_est;
++idx;
}
return best_idx;
}
} // flow
template <typename FLOW>
struct FlowMixin {
static double estimate_of(auto adapter, const auto &children) {
return flow::estimate_of(adapter, children, FLOW(1.0, false));
}
static double estimate_of(const auto &children) {
return estimate_of(flow::DefaultAdapter(), children);
}
static double cost_of(auto adapter, const auto &children, bool strict) {
auto my_adapter = flow::IndirectAdapter(adapter, children);
auto order = flow::make_index(children);
FLOW::sort(my_adapter, order, strict);
return flow::ordered_cost_of(my_adapter, order, FLOW(1.0, strict));
}
static double cost_of(const auto &children, bool strict) {
return cost_of(flow::DefaultAdapter(), children, strict);
}
// TODO: remove
static double cost_of(const auto &children) { return cost_of(children, false); }
};
class AndFlow : public FlowMixin<AndFlow> {
private:
double _flow;
bool _strict;
bool _first;
public:
AndFlow(double in, bool strict) noexcept
: _flow(in), _strict(strict), _first(true) {}
void add(double est) noexcept {
_flow *= est;
_first = false;
}
double flow() const noexcept {
return _flow;
}
bool strict() const noexcept {
return _strict && _first;
}
double estimate() const noexcept {
return _first ? 0.0 : _flow;
}
static void sort(auto adapter, auto &children, bool strict) {
flow::sort<flow::MinAndCost>(adapter, children);
if (strict && children.size() > 1) {
size_t idx = flow::select_strict_and_child(adapter, children);
auto the_one = std::move(children[idx]);
for (; idx > 0; --idx) {
children[idx] = std::move(children[idx-1]);
}
children[0] = std::move(the_one);
}
}
// TODO: add strict
static void sort(auto &children) {
sort(flow::DefaultAdapter(), children, false);
}
};
class OrFlow : public FlowMixin<OrFlow>{
private:
double _flow;
bool _strict;
bool _first;
public:
OrFlow(double in, bool strict) noexcept
: _flow(in), _strict(strict), _first(true) {}
void add(double est) noexcept {
_flow *= (1.0 - est);
_first = false;
}
double flow() const noexcept {
return _flow;
}
bool strict() const noexcept {
return _strict;
}
double estimate() const noexcept {
return _first ? 0.0 : (1.0 - _flow);
}
static void sort(auto adapter, auto &children, bool strict) {
if (strict) {
flow::sort<flow::MinOrStrictCost>(adapter, children);
} else {
flow::sort<flow::MinOrCost>(adapter, children);
}
}
// TODO: add strict
static void sort(auto &children) {
sort(flow::DefaultAdapter(), children, false);
}
};
class AndNotFlow : public FlowMixin<AndNotFlow> {
private:
double _flow;
bool _strict;
bool _first;
public:
AndNotFlow(double in, bool strict) noexcept
: _flow(in), _strict(strict), _first(true) {}
void add(double est) noexcept {
_flow *= _first ? est : (1.0 - est);
_first = false;
}
double flow() const noexcept {
return _flow;
}
bool strict() const noexcept {
return _strict && _first;
}
double estimate() const noexcept {
return _first ? 0.0 : _flow;
}
static void sort(auto adapter, auto &children, bool) {
flow::sort_partial<flow::MinOrCost>(adapter, children, 1);
}
// TODO: add strict
static void sort(auto &children) {
sort(flow::DefaultAdapter(), children, false);
}
};
}
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