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authorPatrick Simianer <p@simianer.de>2012-03-13 09:24:47 +0100
committerPatrick Simianer <p@simianer.de>2012-03-13 09:24:47 +0100
commitc3a9ea64251605532c7954959662643a6a927bb7 (patch)
treefed6048a5acdaf3834740107771c2bc48f26fd4d /utils/agenda.h
parent867bca3e5fa0cdd63bf032e5859fb5092d9a4ca1 (diff)
parenta45af4a3704531a8382cd231f6445b3a33b598a3 (diff)
merge with upstream
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-#ifndef AGENDA_H
-#define AGENDA_H
-
-#define DBG_AGENDA(x) x
-/*
- a priority queue where you expect to queue the same item at different
- priorities several times before finally popping it. higher priority = better.
- so in best first you'd be using negative cost or e^-cost (probabilities, in
- other words).
-
- this means you have a way to look up a key and see its location in the queue,
- so its priority can be adjusted (or, simpler implementation: so when you pop,
- you see if you've already popped before at a lower cost, and skip the
- subsequent pops).
-
- it's assumed that you'll never queue an item @ a better priority after it has
- already been popped. that is, the agenda will track already completed items.
- maybe in the future i will let you recompute a cheaper way to reach things
- after first-pop also, it's assumed that we're always improving prios of
- existing items, never making them worse (even though technically this is
- possible and sensible if it hasn't been popped yet).
-
- simple binary max heap for now. there are better practical options w/
- superior cache locaility. movements in the heap need to update a record for
- that key of where the key went. i do this by creating canonical key pointers
- out of boost object pools (if the key were lightweight e.g. an int, then it
- would make sense to use the hash lookup too
-
- since i'm doing key hashing to start with, i also allow you to attach some
- arbitrary data (value) payload beyond key+priority.
-
- hash map from key to done (has been popped) -> set where doneness is marked in key item?
-
- a slightly different way to make an adjustable heap would be to use
- tree-structured parent/children links intrusively (or mapped by key) in the
- key, rather than indices in a compact binary-tree heap
-
- */
-
-#include "best.h"
-#include "intern_pool.h"
-#include "d_ary_heap.h"
-#include "lvalue_pmap.h"
-#include <vector>
-#include <functional>
-
-/*
-template <class P>
-struct priority_traits {
- typedef typename P::priority_type priority_type;
-};
-*/
-
-typedef best_t agenda_best_t;
-typedef unsigned agenda_location_t;
-
-PMAP_MEMBER_INDIRECT(LocationMap,agenda_location_t,location)
-PMAP_MEMBER_INDIRECT(PriorityMap,agenda_best_t,priority)
-
-struct Less {
- typedef bool result_type;
- template <class A,class B>
- bool operator()(A const& a,B const& b) const { return a<b; }
-};
-
-// LocMap and PrioMap are boost property maps put(locmap,key,size_t), Better(get(priomap,k1),get(priomap,k2)) means k1 should be above k2 (be popped first). Locmap and PrioMap may have state; the rest are assumed stateless functors
-// make sure the (default) location is not -1 for anything you add, or else an assertion may trigger
-template <class Item,class Better=Less, /* intern_pool args */ class KeyF=get_key<Item>,class HashKey=boost::hash<typename KeyF::result_type>,class EqKey=std::equal_to<typename KeyF::result_type>, class Pool=boost::object_pool<Item> >
-struct Agenda : intern_pool<Item,KeyF,HashKey,EqKey,Pool> {
- typedef intern_pool<Item,KeyF,HashKey,EqKey,Pool> Intern; // inherited because I want to use construct()
- /* this is less generic than it could be, because I want to use a single hash mapping to intern to canonical mutable object pointers, where the property maps are just lvalue accessors */
- typedef typename KeyF::result_type Key;
- typedef Item * Handle;
- typedef LocationMap<Handle> LocMap;
- typedef PriorityMap<Handle> PrioMap;
- LocMap locmap;
- PrioMap priomap; // note: priomap[item] is set by caller before giving us the item; then tracks best (for canonicalized item) thereafter
-
- Better better;
- //NOT NEEDED: initialize function object state (there is none)
-
- typedef Item *ItemC; //canonicalized pointer
- typedef Item *ItemP;
- static const std::size_t heap_arity=4; // might be fastest possible (depends on key size probably - cache locality is bad w/ arity=2)
- typedef std::vector<ItemC> HeapStorage;
- typedef d_ary_heap_indirect<Handle,heap_arity,LocMap,PrioMap,Better,HeapStorage,agenda_location_t> Heap;
- Heap q;
-
- // please don't call q.push etc. directly.
- void add(ItemP i) {
- bool fresh=interneq(i);
- DBG_AGENDA(assert(fresh && !q.contains(i)));
- q.push(i);
- }
- bool improve(ItemP i) {
- ItemP c=i;
- bool fresh=interneq(c);
- if (fresh) {
- add(c);
- return true;
- }
- DBG_AGENDA(assert(q.contains(c)));
- return q.maybe_improve(priomap[i]);
- }
- inline bool empty() {
- return q.empty();
- }
- // no need to destroy the canon. item because we want to remember the best cost and reject more expensive ways of using it).
- ItemC pop() {
- ItemC r=q.top();
- q.pop();
- return r;
- }
- void pop_discard() {
- q.pop();
- }
-
- ItemC top() {
- DBG_AGENDA(assert(!empty()));
- return q.top();
- }
-
- agenda_best_t best() const {
- return q.best(); //TODO: cache/track the global best?
- }
-
- agenda_best_t second_best() const {
- return q.second_best();
- }
-
- // add only if worse than queue current best, otherwise evaluate immediately (e.g. for early stopping w/ expensive to compute additional cost). return true if postponed (added)
- bool postpone(ItemP i) {
- if (better(priomap[i],best())) return false;
- return improve(i);
- }
-
- Agenda(unsigned reserve=1000000,LocMap const& lm=LocMap(),PrioMap const& pm=PrioMap(),EqKey const& eq=EqKey(),Better const& better=Better()) : locmap(lm), priomap(pm), better(better), q(priomap,locmap,better,reserve) { }
-};
-
-#endif