use std::cmp; use std::time::Instant; use crate::iter_shortest_paths::astar_bag; const ONE_ATTRIBUTE: u32 = 1000; const MAX_DISTANCE: u32 = 8; fn index_proximity(lhs: u32, rhs: u32) -> u32 { if lhs <= rhs { cmp::min(rhs - lhs, MAX_DISTANCE) } else { cmp::min(lhs - rhs, MAX_DISTANCE) + 1 } } fn positions_proximity(lhs: u32, rhs: u32) -> u32 { let (lhs_attr, lhs_index) = extract_position(lhs); let (rhs_attr, rhs_index) = extract_position(rhs); if lhs_attr != rhs_attr { MAX_DISTANCE } else { index_proximity(lhs_index, rhs_index) } } // Returns the attribute and index parts. fn extract_position(position: u32) -> (u32, u32) { (position / ONE_ATTRIBUTE, position % ONE_ATTRIBUTE) } #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)] enum Node { // Is this node is the first node. Uninit, Init { // The layer where this node located. layer: usize, // The position where this node is located. position: u32, // The total accumulated proximity until this node, used for skipping nodes. acc_proximity: u32, // The parent position from the above layer. parent_position: u32, }, } impl Node { // TODO we must skip the successors that have already been seen // TODO we must skip the successors that doesn't return any documents // this way we are able to skip entire paths fn successors(&self, positions: &[Vec], best_proximity: u32) -> Vec<(Node, u32)> { match self { Node::Uninit => { positions[0].iter().map(|p| { (Node::Init { layer: 0, position: *p, acc_proximity: 0, parent_position: 0 }, 0) }).collect() }, // We reached the highest layer n @ Node::Init { .. } if n.is_complete(positions) => vec![], Node::Init { layer, position, acc_proximity, .. } => { positions[layer + 1].iter().filter_map(|p| { let proximity = positions_proximity(*position, *p); let node = Node::Init { layer: layer + 1, position: *p, acc_proximity: acc_proximity + proximity, parent_position: *position, }; // We do not produce the nodes we have already seen in previous iterations loops. if node.is_complete(positions) && acc_proximity + proximity < best_proximity { None } else { Some((node, proximity)) } }).collect() } } } fn is_complete(&self, positions: &[Vec]) -> bool { match self { Node::Uninit => false, Node::Init { layer, .. } => *layer == positions.len() - 1, } } fn position(&self) -> Option { match self { Node::Uninit => None, Node::Init { position, .. } => Some(*position), } } fn proximity(&self) -> u32 { match self { Node::Uninit => 0, Node::Init { layer, position, acc_proximity, parent_position } => { if layer.checked_sub(1).is_some() { acc_proximity + positions_proximity(*position, *parent_position) } else { 0 } }, } } fn is_reachable(&self, mut contains_documents: F) -> bool where F: FnMut((usize, u32), (usize, u32)) -> bool, { match self { Node::Uninit => true, Node::Init { layer, position, parent_position, .. } => { match layer.checked_sub(1) { Some(parent_layer) => { (contains_documents)((parent_layer, *parent_position), (*layer, *position)) }, None => true, } }, } } } pub struct BestProximity { positions: Vec>, best_proximity: u32, contains_documents: F, } impl BestProximity { pub fn new(positions: Vec>, contains_documents: F) -> BestProximity { let best_proximity = (positions.len() as u32).saturating_sub(1); BestProximity { positions, best_proximity, contains_documents } } } impl Iterator for BestProximity where F: FnMut((usize, u32), (usize, u32)) -> bool + Copy, { type Item = (u32, Vec>); fn next(&mut self) -> Option { let before = Instant::now(); if self.best_proximity == self.positions.len() as u32 * MAX_DISTANCE { return None; } let result = astar_bag( &Node::Uninit, // start |n| n.successors(&self.positions, self.best_proximity), |_| 0, // heuristic |n| { // success let c = n.is_complete(&self.positions) && n.proximity() >= self.best_proximity; if n.is_reachable(self.contains_documents) { Some(c) } else { None } }, ); eprintln!("BestProximity::next() took {:.02?}", before.elapsed()); match result { Some((paths, proximity)) => { self.best_proximity = proximity + 1; // We retrieve the last path that we convert into a Vec let paths: Vec<_> = paths.map(|p| p.iter().filter_map(Node::position).collect()).collect(); eprintln!("result: {} {:?}", proximity, paths); Some((proximity, paths)) }, None => { eprintln!("result: {:?}", None as Option<()>); self.best_proximity += 1; None }, } } } #[cfg(test)] mod tests { use super::*; #[test] fn same_attribute() { let positions = vec![ vec![0, 2, 3, 4 ], vec![ 1, ], vec![ 3, 6], ]; let mut iter = BestProximity::new(positions, |_, _| true); assert_eq!(iter.next(), Some((1+2, vec![vec![0, 1, 3]]))); // 3 assert_eq!(iter.next(), Some((2+2, vec![vec![2, 1, 3]]))); // 4 assert_eq!(iter.next(), Some((3+2, vec![vec![3, 1, 3]]))); // 5 assert_eq!(iter.next(), Some((1+5, vec![vec![0, 1, 6], vec![4, 1, 3]]))); // 6 assert_eq!(iter.next(), Some((2+5, vec![vec![2, 1, 6]]))); // 7 assert_eq!(iter.next(), Some((3+5, vec![vec![3, 1, 6]]))); // 8 assert_eq!(iter.next(), Some((4+5, vec![vec![4, 1, 6]]))); // 9 assert_eq!(iter.next(), None); } #[test] fn different_attributes() { let positions = vec![ vec![0, 2, 1000, 1001, 2000 ], vec![ 1, 1000, 2001 ], vec![ 3, 6, 2002, 3000], ]; let mut iter = BestProximity::new(positions, |_, _| true); assert_eq!(iter.next(), Some((1+1, vec![vec![2000, 2001, 2002]]))); // 2 assert_eq!(iter.next(), Some((1+2, vec![vec![0, 1, 3]]))); // 3 assert_eq!(iter.next(), Some((2+2, vec![vec![2, 1, 3]]))); // 4 assert_eq!(iter.next(), Some((1+5, vec![vec![0, 1, 6]]))); // 6 // We ignore others here... } #[test] fn easy_proximities() { fn slice_proximity(positions: &[u32]) -> u32 { positions.windows(2).map(|ps| positions_proximity(ps[0], ps[1])).sum::() } assert_eq!(slice_proximity(&[1000, 1000, 2002]), 8); } }