// through the collection, for every collection type that supports
// this.
-#![feature(vecmap)]
+// HIGH LEVEL DESCRIPTION OF THE TEST ARCHITECTURE
+// -----------------------------------------------
+//
+// We pick a data structure and want to make a cyclic construction
+// from it. Each test of interest is labelled starting with "Cycle N:
+// { ... }" where N is the test number and the "..."`is filled in with
+// a graphviz-style description of the graph structure that the
+// author believes is being made. So "{ a -> b, b -> (c,d), (c,d) -> e }"
+// describes a line connected to a diamond:
+//
+// c
+// / \
+// a - b e
+// \ /
+// d
+//
+// (Note that the above directed graph is actually acyclic.)
+//
+// The different graph structures are often composed of different data
+// types. Some may be built atop `Vec`, others atop `HashMap`, etc.
+//
+// For each graph structure, we actually *confirm* that a cycle exists
+// (as a safe-guard against a test author accidentally leaving it out)
+// by traversing each graph and "proving" that a cycle exists within it.
+//
+// To do this, while trying to keep the code uniform (despite working
+// with different underlying collection and smart-pointer types), we
+// have a standard traversal API:
+//
+// 1. every node in the graph carries a `mark` (a u32, init'ed to 0).
+//
+// 2. every node provides a method to visit its children
+//
+// 3. a traversal attmepts to visit the nodes of the graph and prove that
+// it sees the same node twice. It does this by setting the mark of each
+// node to a fresh non-zero value, and if it sees the current mark, it
+// "knows" that it must have found a cycle, and stops attempting further
+// traversal.
+//
+// 4. each traversal is controlled by a bit-string that tells it which child
+// it visit when it can take different paths. As a simple example,
+// in a binary tree, 0 could mean "left" (and 1, "right"), so that
+// "00010" means "left, left, left, right, left". (In general it will
+// read as many bits as it needs to choose one child.)
+//
+// The graphs in this test are all meant to be very small, and thus
+// short bitstrings of less than 64 bits should always suffice.
+//
+// (An earlier version of this test infrastructure simply had any
+// given traversal visit all children it encountered, in a
+// depth-first manner; one problem with this approach is that an
+// acyclic graph can still have sharing, which would then be treated
+// as a repeat mark and reported as a detected cycle.)
+//
+// The travseral code is a little more complicated because it has been
+// programmed in a somewhat defensive manner. For example it also has
+// a max threshold for the number of nodes it will visit, to guard
+// against scenarios where the nodes are not correctly setting their
+// mark when asked. There are various other methods not discussed here
+// that are for aiding debugging the test when it runs, such as the
+// `name` method that all nodes provide.
+//
+// So each test:
+//
+// 1. allocates the nodes in the graph,
+//
+// 2. sets up the links in the graph,
+//
+// 3. clones the "ContextData"
+//
+// 4. chooses a new current mark value for this test
+//
+// 5. initiates a traversal, potentially from multiple starting points
+// (aka "roots"), with a given control-string (potentially a
+// different string for each root). if it does start from a
+// distinct root, then such a test should also increment the
+// current mark value, so that this traversal is considered
+// distinct from the prior one on this graph structure.
+//
+// Note that most of the tests work with the default control string
+// of all-zeroes.
+//
+// 6. assert that the context confirms that it actually saw a cycle (since a traversal
+// might have terminated, e.g. on a tree structure that contained no cycles).
-use std::cell::Cell;
+use std::cell::{Cell, RefCell};
use std::cmp::Ordering;
use std::collections::BinaryHeap;
use std::collections::HashMap;
use std::collections::btree_map::BTreeMap;
use std::collections::btree_set::BTreeSet;
use std::hash::{Hash, Hasher};
+use std::rc::Rc;
+use std::sync::{Arc, RwLock, Mutex};
const PRINT: bool = false;
skipped: 0,
curr_mark: 0,
saw_prev_marked: false,
+ control_bits: 0,
};
+ // SANITY CHECK FOR TEST SUITE (thus unnumbered)
+ // Not a cycle: { v[0] -> (v[1], v[2]), v[1] -> v[3], v[2] -> v[3] };
+ let v: Vec<S2> = vec![Named::new("s0"),
+ Named::new("s1"),
+ Named::new("s2"),
+ Named::new("s3")];
+ v[0].next.set((Some(&v[1]), Some(&v[2])));
+ v[1].next.set((Some(&v[3]), None));
+ v[2].next.set((Some(&v[3]), None));
+ v[3].next.set((None, None));
+
+ let mut c = c_orig.clone();
+ c.curr_mark = 10;
+ assert!(!c.saw_prev_marked);
+ v[0].descend_into_self(&mut c);
+ assert!(!c.saw_prev_marked); // <-- different from below, b/c acyclic above
+
+ if PRINT { println!(""); }
+
// Cycle 1: { v[0] -> v[1], v[1] -> v[0] };
// does not exercise `v` itself
let v: Vec<S> = vec![Named::new("s0"),
let mut c = c_orig.clone();
c.curr_mark = 10;
assert!(!c.saw_prev_marked);
- v[0].for_each_child(&mut c);
+ v[0].descend_into_self(&mut c);
assert!(c.saw_prev_marked);
if PRINT { println!(""); }
let mut c = c_orig.clone();
c.curr_mark = 20;
assert!(!c.saw_prev_marked);
- v.for_each_child(&mut c);
+ v.descend_into_self(&mut c);
assert!(c.saw_prev_marked);
if PRINT { println!(""); }
for (key, _) in h.iter() {
c.curr_mark += 1;
c.saw_prev_marked = false;
- key.for_each_child(&mut c);
+ key.descend_into_self(&mut c);
assert!(c.saw_prev_marked);
}
for (key, _) in h.iter() {
c.curr_mark += 1;
c.saw_prev_marked = false;
- key.for_each_child(&mut c);
+ key.descend_into_self(&mut c);
assert!(c.saw_prev_marked);
// break;
}
let mut c = c_orig.clone();
c.curr_mark = 50;
assert!(!c.saw_prev_marked);
- vd[0].for_each_child(&mut c);
+ vd[0].descend_into_self(&mut c);
assert!(c.saw_prev_marked);
if PRINT { println!(""); }
let mut c = c_orig.clone();
c.curr_mark = 60;
assert!(!c.saw_prev_marked);
- vd[0].for_each_child(&mut c);
+ vd[0].descend_into_self(&mut c);
assert!(c.saw_prev_marked);
if PRINT { println!(""); }
let mut c = c_orig.clone();
c.curr_mark = 70;
assert!(!c.saw_prev_marked);
- vm[&0].for_each_child(&mut c);
+ vm[&0].descend_into_self(&mut c);
assert!(c.saw_prev_marked);
if PRINT { println!(""); }
for e in &ll {
c.curr_mark += 1;
c.saw_prev_marked = false;
- e.for_each_child(&mut c);
+ e.descend_into_self(&mut c);
assert!(c.saw_prev_marked);
// break;
}
for b in &bh {
c.curr_mark += 1;
c.saw_prev_marked = false;
- b.for_each_child(&mut c);
+ b.descend_into_self(&mut c);
assert!(c.saw_prev_marked);
// break;
}
for (k, _) in &btm {
c.curr_mark += 1;
c.saw_prev_marked = false;
- k.for_each_child(&mut c);
+ k.descend_into_self(&mut c);
assert!(c.saw_prev_marked);
// break;
}
for b in &bts {
c.curr_mark += 1;
c.saw_prev_marked = false;
- b.for_each_child(&mut c);
+ b.descend_into_self(&mut c);
assert!(c.saw_prev_marked);
// break;
}
+
+ if PRINT { println!(""); }
+
+ // Cycle 11: { rc0 -> (rc1, rc2), rc1 -> (), rc2 -> rc0 }
+ let (rc0, rc1, rc2): (RCRC, RCRC, RCRC);
+ rc0 = RCRC::new("rcrc0");
+ rc1 = RCRC::new("rcrc1");
+ rc2 = RCRC::new("rcrc2");
+ rc0.0.borrow_mut().children.0 = Some(&rc1);
+ rc0.0.borrow_mut().children.1 = Some(&rc2);
+ rc2.0.borrow_mut().children.0 = Some(&rc0);
+
+ let mut c = c_orig.clone();
+ c.control_bits = 0b1;
+ c.curr_mark = 110;
+ assert!(!c.saw_prev_marked);
+ rc0.descend_into_self(&mut c);
+ assert!(c.saw_prev_marked);
+
+ if PRINT { println!(""); }
+
+ // We want to take the previous Rc case and generalize it to Arc.
+ //
+ // We can use refcells if we're single-threaded (as this test is).
+ // If one were to generalize these constructions to a
+ // multi-threaded context, then it might seem like we could choose
+ // between either a RwLock or a Mutex to hold the owned arcs on
+ // each node.
+ //
+ // Part of the point of this test is to actually confirm that the
+ // cycle exists by traversing it. We can do that just fine with an
+ // RwLock (since we can grab the child pointers in read-only
+ // mode), but we cannot lock a std::sync::Mutex to guard reading
+ // from each node via the same pattern, since once you hit the
+ // cycle, you'll be trying to acquring the same lock twice.
+ // (We deal with this by exiting the traversal early if try_lock fails.)
+
+ // Cycle 12: { arc0 -> (arc1, arc2), arc1 -> (), arc2 -> arc0 }, refcells
+ let (arc0, arc1, arc2): (ARCRC, ARCRC, ARCRC);
+ arc0 = ARCRC::new("arcrc0");
+ arc1 = ARCRC::new("arcrc1");
+ arc2 = ARCRC::new("arcrc2");
+ arc0.0.borrow_mut().children.0 = Some(&arc1);
+ arc0.0.borrow_mut().children.1 = Some(&arc2);
+ arc2.0.borrow_mut().children.0 = Some(&arc0);
+
+ let mut c = c_orig.clone();
+ c.control_bits = 0b1;
+ c.curr_mark = 110;
+ assert!(!c.saw_prev_marked);
+ arc0.descend_into_self(&mut c);
+ assert!(c.saw_prev_marked);
+
+ if PRINT { println!(""); }
+
+ // Cycle 13: { arc0 -> (arc1, arc2), arc1 -> (), arc2 -> arc0 }, rwlocks
+ let (arc0, arc1, arc2): (ARCRW, ARCRW, ARCRW);
+ arc0 = ARCRW::new("arcrw0");
+ arc1 = ARCRW::new("arcrw1");
+ arc2 = ARCRW::new("arcrw2");
+ arc0.0.write().unwrap().children.0 = Some(&arc1);
+ arc0.0.write().unwrap().children.1 = Some(&arc2);
+ arc2.0.write().unwrap().children.0 = Some(&arc0);
+
+ let mut c = c_orig.clone();
+ c.control_bits = 0b1;
+ c.curr_mark = 110;
+ assert!(!c.saw_prev_marked);
+ arc0.descend_into_self(&mut c);
+ assert!(c.saw_prev_marked);
+
+ if PRINT { println!(""); }
+
+ // Cycle 14: { arc0 -> (arc1, arc2), arc1 -> (), arc2 -> arc0 }, mutexs
+ let (arc0, arc1, arc2): (ARCM, ARCM, ARCM);
+ arc0 = ARCM::new("arcm0");
+ arc1 = ARCM::new("arcm1");
+ arc2 = ARCM::new("arcm2");
+ arc0.1.lock().unwrap().children.0 = Some(&arc1);
+ arc0.1.lock().unwrap().children.1 = Some(&arc2);
+ arc2.1.lock().unwrap().children.0 = Some(&arc0);
+
+ let mut c = c_orig.clone();
+ c.control_bits = 0b1;
+ c.curr_mark = 110;
+ assert!(!c.saw_prev_marked);
+ arc0.descend_into_self(&mut c);
+ assert!(c.saw_prev_marked);
}
trait Named {
fn set_mark(&self, mark: u32) { self.mark.set(mark); }
}
+struct S2<'a> {
+ name: &'static str,
+ mark: Cell<u32>,
+ next: Cell<(Option<&'a S2<'a>>, Option<&'a S2<'a>>)>,
+}
+
+impl<'a> Named for S2<'a> {
+ fn new<'b>(name: &'static str) -> S2<'b> {
+ S2 { name: name, mark: Cell::new(0), next: Cell::new((None, None)) }
+ }
+ fn name(&self) -> &str { self.name }
+}
+
+impl<'a> Marked<u32> for S2<'a> {
+ fn mark(&self) -> u32 { self.mark.get() }
+ fn set_mark(&self, mark: u32) {
+ self.mark.set(mark);
+ }
+}
+
struct V<'a> {
name: &'static str,
mark: Cell<u32>,
}
}
+#[derive(Clone)]
+struct RCRCData<'a> {
+ name: &'static str,
+ mark: Cell<u32>,
+ children: (Option<&'a RCRC<'a>>, Option<&'a RCRC<'a>>),
+}
+#[derive(Clone)]
+struct RCRC<'a>(Rc<RefCell<RCRCData<'a>>>);
+
+impl<'a> Named for RCRC<'a> {
+ fn new(name: &'static str) -> Self {
+ RCRC(Rc::new(RefCell::new(RCRCData {
+ name: name, mark: Cell::new(0), children: (None, None), })))
+ }
+ fn name(&self) -> &str { self.0.borrow().name }
+}
+
+impl<'a> Marked<u32> for RCRC<'a> {
+ fn mark(&self) -> u32 { self.0.borrow().mark.get() }
+ fn set_mark(&self, mark: u32) { self.0.borrow().mark.set(mark); }
+}
+
+impl<'a> Children<'a> for RCRC<'a> {
+ fn count_children(&self) -> usize { 2 }
+ fn descend_one_child<C>(&self, context: &mut C, index: usize)
+ where C: Context + PrePost<Self>, Self: Sized
+ {
+ let children = &self.0.borrow().children;
+ let child = match index {
+ 0 => if let Some(child) = children.0 { child } else { return; },
+ 1 => if let Some(child) = children.1 { child } else { return; },
+ _ => panic!("bad children"),
+ };
+ // println!("S2 {} descending into child {} at index {}", self.name, child.name, index);
+ child.descend_into_self(context);
+ }
+}
+#[derive(Clone)]
+struct ARCRCData<'a> {
+ name: &'static str,
+ mark: Cell<u32>,
+ children: (Option<&'a ARCRC<'a>>, Option<&'a ARCRC<'a>>),
+}
+#[derive(Clone)]
+struct ARCRC<'a>(Arc<RefCell<ARCRCData<'a>>>);
+
+impl<'a> Named for ARCRC<'a> {
+ fn new(name: &'static str) -> Self {
+ ARCRC(Arc::new(RefCell::new(ARCRCData {
+ name: name, mark: Cell::new(0), children: (None, None), })))
+ }
+ fn name(&self) -> &str { self.0.borrow().name }
+}
+
+impl<'a> Marked<u32> for ARCRC<'a> {
+ fn mark(&self) -> u32 { self.0.borrow().mark.get() }
+ fn set_mark(&self, mark: u32) { self.0.borrow().mark.set(mark); }
+}
+
+impl<'a> Children<'a> for ARCRC<'a> {
+ fn count_children(&self) -> usize { 2 }
+ fn descend_one_child<C>(&self, context: &mut C, index: usize)
+ where C: Context + PrePost<Self>, Self: Sized
+ {
+ let children = &self.0.borrow().children;
+ match index {
+ 0 => if let Some(ref child) = children.0 {
+ child.descend_into_self(context);
+ },
+ 1 => if let Some(ref child) = children.1 {
+ child.descend_into_self(context);
+ },
+ _ => panic!("bad children!"),
+ }
+ }
+}
+
+#[derive(Clone)]
+struct ARCMData<'a> {
+ mark: Cell<u32>,
+ children: (Option<&'a ARCM<'a>>, Option<&'a ARCM<'a>>),
+}
+
+#[derive(Clone)]
+struct ARCM<'a>(&'static str, Arc<Mutex<ARCMData<'a>>>);
+
+impl<'a> Named for ARCM<'a> {
+ fn new(name: &'static str) -> Self {
+ ARCM(name, Arc::new(Mutex::new(ARCMData {
+ mark: Cell::new(0), children: (None, None), })))
+ }
+ fn name(&self) -> &str { self.0 }
+}
+
+impl<'a> Marked<u32> for ARCM<'a> {
+ fn mark(&self) -> u32 { self.1.lock().unwrap().mark.get() }
+ fn set_mark(&self, mark: u32) { self.1.lock().unwrap().mark.set(mark); }
+}
+
+impl<'a> Children<'a> for ARCM<'a> {
+ fn count_children(&self) -> usize { 2 }
+ fn descend_one_child<C>(&self, context: &mut C, index: usize)
+ where C: Context + PrePost<Self>, Self: Sized
+ {
+ let ref children = if let Ok(data) = self.1.try_lock() {
+ data.children
+ } else { return; };
+ match index {
+ 0 => if let Some(ref child) = children.0 {
+ child.descend_into_self(context);
+ },
+ 1 => if let Some(ref child) = children.1 {
+ child.descend_into_self(context);
+ },
+ _ => panic!("bad children!"),
+ }
+ }
+}
+
+#[derive(Clone)]
+struct ARCRWData<'a> {
+ name: &'static str,
+ mark: Cell<u32>,
+ children: (Option<&'a ARCRW<'a>>, Option<&'a ARCRW<'a>>),
+}
+
+#[derive(Clone)]
+struct ARCRW<'a>(Arc<RwLock<ARCRWData<'a>>>);
+
+impl<'a> Named for ARCRW<'a> {
+ fn new(name: &'static str) -> Self {
+ ARCRW(Arc::new(RwLock::new(ARCRWData {
+ name: name, mark: Cell::new(0), children: (None, None), })))
+ }
+ fn name(&self) -> &str { self.0.read().unwrap().name }
+}
+
+impl<'a> Marked<u32> for ARCRW<'a> {
+ fn mark(&self) -> u32 { self.0.read().unwrap().mark.get() }
+ fn set_mark(&self, mark: u32) { self.0.read().unwrap().mark.set(mark); }
+}
+
+impl<'a> Children<'a> for ARCRW<'a> {
+ fn count_children(&self) -> usize { 2 }
+ fn descend_one_child<C>(&self, context: &mut C, index: usize)
+ where C: Context + PrePost<Self>, Self: Sized
+ {
+ let children = &self.0.read().unwrap().children;
+ match index {
+ 0 => if let Some(ref child) = children.0 {
+ child.descend_into_self(context);
+ },
+ 1 => if let Some(ref child) = children.1 {
+ child.descend_into_self(context);
+ },
+ _ => panic!("bad children!"),
+ }
+ }
+}
trait Context {
+ fn next_index(&mut self, len: usize) -> usize;
fn should_act(&self) -> bool;
fn increase_visited(&mut self);
fn increase_skipped(&mut self);
}
trait Children<'a> {
- fn for_each_child<C>(&self, context: &mut C)
+ fn count_children(&self) -> usize;
+ fn descend_one_child<C>(&self, context: &mut C, index: usize)
where C: Context + PrePost<Self>, Self: Sized;
+ fn next_child<C>(&self, context: &mut C)
+ where C: Context + PrePost<Self>, Self: Sized
+ {
+ let index = context.next_index(self.count_children());
+ self.descend_one_child(context, index);
+ }
+
fn descend_into_self<C>(&self, context: &mut C)
where C: Context + PrePost<Self>, Self: Sized
{
if context.should_act() {
context.increase_visited();
context.increase_depth();
- self.for_each_child(context);
+ self.next_child(context);
context.decrease_depth();
} else {
context.hit_limit(self);
}
impl<'a> Children<'a> for S<'a> {
- fn for_each_child<C>(&self, context: &mut C)
- where C: Context + PrePost<S<'a>>
+ fn count_children(&self) -> usize { 1 }
+ fn descend_one_child<C>(&self, context: &mut C, _: usize)
+ where C: Context + PrePost<Self>, Self: Sized {
+ self.descend(&self.next, context);
+ }
+}
+
+impl<'a> Children<'a> for S2<'a> {
+ fn count_children(&self) -> usize { 2 }
+ fn descend_one_child<C>(&self, context: &mut C, index: usize)
+ where C: Context + PrePost<Self>, Self: Sized
{
- self.descend(&self.next, context);
+ let children = self.next.get();
+ let child = match index {
+ 0 => if let Some(child) = children.0 { child } else { return; },
+ 1 => if let Some(child) = children.1 { child } else { return; },
+ _ => panic!("bad children"),
+ };
+ // println!("S2 {} descending into child {} at index {}", self.name, child.name, index);
+ child.descend_into_self(context);
}
}
impl<'a> Children<'a> for V<'a> {
- fn for_each_child<C>(&self, context: &mut C)
- where C: Context + PrePost<V<'a>>
+ fn count_children(&self) -> usize { self.contents.len() }
+ fn descend_one_child<C>(&self, context: &mut C, index: usize)
+ where C: Context + PrePost<Self>, Self: Sized
{
- for r in &self.contents {
- self.descend(r, context);
+ if let Some(child) = self.contents[index].get() {
+ child.descend_into_self(context);
}
}
}
impl<'a> Children<'a> for H<'a> {
- fn for_each_child<C>(&self, context: &mut C)
- where C: Context + PrePost<H<'a>>
+ fn count_children(&self) -> usize { 1 }
+ fn descend_one_child<C>(&self, context: &mut C, _: usize)
+ where C: Context + PrePost<Self>, Self: Sized
{
self.descend(&self.next, context);
}
}
impl<'a> Children<'a> for HM<'a> {
- fn for_each_child<C>(&self, context: &mut C)
- where C: Context + PrePost<HM<'a>>
+ fn count_children(&self) -> usize {
+ if let Some(m) = self.contents.get() { 2 * m.iter().count() } else { 0 }
+ }
+ fn descend_one_child<C>(&self, context: &mut C, index: usize)
+ where C: Context + PrePost<Self>, Self: Sized
{
if let Some(ref hm) = self.contents.get() {
- for (k, v) in hm.iter() {
- for r in &[k, v] {
- r.descend_into_self(context);
- }
+ for (k, v) in hm.iter().nth(index / 2) {
+ [k, v][index % 2].descend_into_self(context);
}
}
}
}
impl<'a> Children<'a> for VD<'a> {
- fn for_each_child<C>(&self, context: &mut C)
- where C: Context + PrePost<VD<'a>>
+ fn count_children(&self) -> usize {
+ if let Some(d) = self.contents.get() { d.iter().count() } else { 0 }
+ }
+ fn descend_one_child<C>(&self, context: &mut C, index: usize)
+ where C: Context + PrePost<Self>, Self: Sized
{
if let Some(ref vd) = self.contents.get() {
- for r in vd.iter() {
+ for r in vd.iter().nth(index) {
r.descend_into_self(context);
}
}
}
impl<'a> Children<'a> for VM<'a> {
- fn for_each_child<C>(&self, context: &mut C)
+ fn count_children(&self) -> usize {
+ if let Some(m) = self.contents.get() { m.iter().count() } else { 0 }
+ }
+ fn descend_one_child<C>(&self, context: &mut C, index: usize)
where C: Context + PrePost<VM<'a>>
{
if let Some(ref vd) = self.contents.get() {
- for (_idx, r) in vd.iter() {
+ for (_idx, r) in vd.iter().nth(index) {
r.descend_into_self(context);
}
}
}
impl<'a> Children<'a> for LL<'a> {
- fn for_each_child<C>(&self, context: &mut C)
+ fn count_children(&self) -> usize {
+ if let Some(l) = self.contents.get() { l.iter().count() } else { 0 }
+ }
+ fn descend_one_child<C>(&self, context: &mut C, index: usize)
where C: Context + PrePost<LL<'a>>
{
if let Some(ref ll) = self.contents.get() {
- for r in ll.iter() {
+ for r in ll.iter().nth(index) {
r.descend_into_self(context);
}
}
}
impl<'a> Children<'a> for BH<'a> {
- fn for_each_child<C>(&self, context: &mut C)
+ fn count_children(&self) -> usize {
+ if let Some(h) = self.contents.get() { h.iter().count() } else { 0 }
+ }
+ fn descend_one_child<C>(&self, context: &mut C, index: usize)
where C: Context + PrePost<BH<'a>>
{
if let Some(ref bh) = self.contents.get() {
- for r in bh.iter() {
+ for r in bh.iter().nth(index) {
r.descend_into_self(context);
}
}
}
impl<'a> Children<'a> for BTM<'a> {
- fn for_each_child<C>(&self, context: &mut C)
+ fn count_children(&self) -> usize {
+ if let Some(m) = self.contents.get() { 2 * m.iter().count() } else { 0 }
+ }
+ fn descend_one_child<C>(&self, context: &mut C, index: usize)
where C: Context + PrePost<BTM<'a>>
{
if let Some(ref bh) = self.contents.get() {
- for (k, v) in bh.iter() {
- for r in &[k, v] {
- r.descend_into_self(context);
- }
+ for (k, v) in bh.iter().nth(index / 2) {
+ [k, v][index % 2].descend_into_self(context);
}
}
}
}
impl<'a> Children<'a> for BTS<'a> {
- fn for_each_child<C>(&self, context: &mut C)
+ fn count_children(&self) -> usize {
+ if let Some(s) = self.contents.get() { s.iter().count() } else { 0 }
+ }
+ fn descend_one_child<C>(&self, context: &mut C, index: usize)
where C: Context + PrePost<BTS<'a>>
{
if let Some(ref bh) = self.contents.get() {
- for r in bh.iter() {
+ for r in bh.iter().nth(index) {
r.descend_into_self(context);
}
}
skipped: usize,
curr_mark: u32,
saw_prev_marked: bool,
+ control_bits: u64,
}
impl Context for ContextData {
+ fn next_index(&mut self, len: usize) -> usize {
+ if len < 2 { return 0; }
+ let mut pow2 = len.next_power_of_two();
+ let _pow2_orig = pow2;
+ let mut idx = 0;
+ let mut bits = self.control_bits;
+ while pow2 > 1 {
+ idx = (idx << 1) | (bits & 1) as usize;
+ bits = bits >> 1;
+ pow2 = pow2 >> 1;
+ }
+ idx = idx % len;
+ // println!("next_index({} [{:b}]) says {}, pre(bits): {:b} post(bits): {:b}",
+ // len, _pow2_orig, idx, self.control_bits, bits);
+ self.control_bits = bits;
+ return idx;
+ }
fn should_act(&self) -> bool {
self.curr_depth < self.max_depth && self.visited < self.max_visits
}
projects / rust.git / commitdiff