aljaz/lightning
1
0
Fork 0
mirror of https://github.com/aljazceru/lightning.git synced 2025-12-19 15:14:23 +01:00
Code Issues Packages Projects Releases Wiki Activity

dijkstra: fix heap ordering.

Browse Source 
We were always ordering heap by distance, not score (which are different
if we are routing by cheapest, not shortest!).

This simplifies our callbacks, too.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2020-10-20 14:28:06 +10:30
parent 4a1843a151
commit 1bf3eebbf6
6 changed files with 49 additions and 85 deletions
Download Patch File Download Diff File Expand all files Collapse all files

38
common/dijkstra.c
View File

@@ -22,6 +22,9 @@ struct dijkstra {
/* NULL means it's been visited already. */ /* NULL means it's been visited already. */
const struct gossmap_node **heapptr; const struct gossmap_node **heapptr;
/* How we decide "best" */
u64 score;
/* We could re-evaluate to determine this, but keeps it simple */ /* We could re-evaluate to determine this, but keeps it simple */
struct gossmap_chan *best_chan; struct gossmap_chan *best_chan;
}; };
@@ -67,9 +70,9 @@ static int less_comparer(const void *const ctx,
const void *const b) const void *const b)
{ {
return get_dijkstra(global_dijkstra, global_map, return get_dijkstra(global_dijkstra, global_map,
*(struct gossmap_node **)a)->distance *(struct gossmap_node **)a)->score
> get_dijkstra(global_dijkstra, global_map, > get_dijkstra(global_dijkstra, global_map,
*(struct gossmap_node **)b)->distance; *(struct gossmap_node **)b)->score;
} }
static void item_mover(void *const dst, const void *const src) static void item_mover(void *const dst, const void *const src)
@@ -101,6 +104,7 @@ static const struct gossmap_node **mkheap(const tal_t *ctx,
d->distance = 0; d->distance = 0;
d->total_delay = 0; d->total_delay = 0;
d->cost = sent; d->cost = sent;
d->score = 0;
i--; i--;
} else { } else {
heap[i] = n; heap[i] = n;
@@ -108,6 +112,7 @@ static const struct gossmap_node **mkheap(const tal_t *ctx,
d->distance = UINT_MAX; d->distance = UINT_MAX;
d->cost = AMOUNT_MSAT(-1ULL); d->cost = AMOUNT_MSAT(-1ULL);
d->total_delay = 0; d->total_delay = 0;
d->score = -1ULL;
} }
} }
assert(i == tal_count(heap)); assert(i == tal_count(heap));
@@ -142,13 +147,9 @@ dijkstra_(const tal_t *ctx,
int dir, int dir,
struct amount_msat amount, struct amount_msat amount,
void *arg), void *arg),
bool (*path_better)(u32 old_distance, u64 (*path_score)(u32 distance,
u32 new_distance, struct amount_msat cost,
struct amount_msat old_cost, struct amount_msat risk),
struct amount_msat new_cost,
struct amount_msat old_risk,
struct amount_msat new_risk,
void *arg),
void *arg) void *arg)
{ {
struct dijkstra *dij; struct dijkstra *dij;
@@ -229,7 +230,8 @@ dijkstra_(const tal_t *ctx,
int which_half; int which_half;
struct gossmap_chan *c; struct gossmap_chan *c;
struct dijkstra *d; struct dijkstra *d;
struct amount_msat cost, new_risk, old_risk; struct amount_msat cost, risk;
u64 score;
c = gossmap_nth_chan(map, cur, i, &which_half); c = gossmap_nth_chan(map, cur, i, &which_half);
neighbor = gossmap_nth_node(map, c, !which_half); neighbor = gossmap_nth_node(map, c, !which_half);
@@ -251,20 +253,11 @@ dijkstra_(const tal_t *ctx,
continue; continue;
/* cltv_delay can't overflow: only 20 bits per hop. */ /* cltv_delay can't overflow: only 20 bits per hop. */
new_risk = risk_price(cost, riskfactor, risk = risk_price(cost, riskfactor,
cur_d->total_delay cur_d->total_delay
+ c->half[!which_half].delay); + c->half[!which_half].delay);
score = path_score(cur_d->distance + 1, cost, risk);
old_risk = risk_price(d->cost, riskfactor, if (score >= d->score)
d->total_delay);
if (!path_better(d->distance,
cur_d->distance + 1,
d->cost,
cost,
old_risk,
new_risk,
arg))
continue; continue;
d->distance = cur_d->distance + 1; d->distance = cur_d->distance + 1;
@@ -272,6 +265,7 @@ dijkstra_(const tal_t *ctx,
+ c->half[!which_half].delay; + c->half[!which_half].delay;
d->cost = cost; d->cost = cost;
d->best_chan = c; d->best_chan = c;
d->score = score;
gheap_restore_heap_after_item_increase(&gheap_ctx, gheap_restore_heap_after_item_increase(&gheap_ctx,
heap, heapsize, heap, heapsize,
d->heapptr - heap); d->heapptr - heap);

19
common/dijkstra.h
View File

@@ -21,28 +21,19 @@ dijkstra_(const tal_t *ctx,
int dir, int dir,
struct amount_msat amount, struct amount_msat amount,
void *arg), void *arg),
bool (*path_better)(u32 old_distance, u64 (*path_score)(u32 distance,
u32 new_distance, struct amount_msat cost,
struct amount_msat old_cost, struct amount_msat risk),
struct amount_msat new_cost,
struct amount_msat old_risk,
struct amount_msat new_risk,
void *arg),
void *arg); void *arg);
#define dijkstra(ctx, map, start, amount, riskfactor, channel_ok, \ #define dijkstra(ctx, map, start, amount, riskfactor, channel_ok, \
path_better, arg) \ path_score, arg) \
dijkstra_((ctx), (map), (start), (amount), (riskfactor), \ dijkstra_((ctx), (map), (start), (amount), (riskfactor), \
typesafe_cb_preargs(bool, void *, (channel_ok), (arg), \ typesafe_cb_preargs(bool, void *, (channel_ok), (arg), \
const struct gossmap *, \ const struct gossmap *, \
const struct gossmap_chan *, \ const struct gossmap_chan *, \
int, struct amount_msat), \ int, struct amount_msat), \
typesafe_cb_preargs(bool, void *, (path_better), (arg), \ (path_score), \
u32, u32, \
struct amount_msat, \
struct amount_msat, \
struct amount_msat, \
struct amount_msat), \
(arg)) (arg))
/* Returns UINT_MAX if unreachable. */ /* Returns UINT_MAX if unreachable. */

47
common/route.c
View File

@@ -37,43 +37,28 @@ bool route_can_carry(const struct gossmap *map,
return route_can_carry_even_disabled(map, c, dir, amount, arg); return route_can_carry_even_disabled(map, c, dir, amount, arg);
} }
bool route_path_shorter(u32 old_distance, u32 new_distance, /* Prioritize distance over costs */
struct amount_msat old_cost, u64 route_score_shorter(u32 distance,
struct amount_msat new_cost, struct amount_msat cost,
struct amount_msat old_risk, struct amount_msat risk)
struct amount_msat new_risk,
void *unused)
{ {
if (new_distance > old_distance) u64 costs = cost.millisatoshis + risk.millisatoshis; /* Raw: score */
return false; if (costs > 0xFFFFFFFF)
if (new_distance < old_distance) costs = 0xFFFFFFFF;
return true;
/* Tiebreak by cost */ return costs + ((u64)distance << 32);
if (!amount_msat_add(&old_cost, old_cost, old_risk)
|| !amount_msat_add(&new_cost, new_cost, new_risk))
return false;
return amount_msat_less(new_cost, old_cost);
} }
bool route_path_cheaper(u32 old_distance, u32 new_distance, /* Prioritize costs over distance */
struct amount_msat old_cost, u64 route_score_cheaper(u32 distance,
struct amount_msat new_cost, struct amount_msat cost,
struct amount_msat old_risk, struct amount_msat risk)
struct amount_msat new_risk,
void *unused)
{ {
if (!amount_msat_add(&old_cost, old_cost, old_risk) u64 costs = cost.millisatoshis + risk.millisatoshis; /* Raw: score */
|| !amount_msat_add(&new_cost, new_cost, new_risk)) if (costs > 0xFFFFFFFF)
return false; costs = 0xFFFFFFFF;
if (amount_msat_greater(new_cost, old_cost)) return (costs << 32) + distance;
return false;
if (amount_msat_less(new_cost, old_cost))
return true;
/* Tiebreak by distance */
return new_distance < old_distance;
} }
struct route **route_from_dijkstra(const struct gossmap *map, struct route **route_from_dijkstra(const struct gossmap *map,

18
common/route.h
View File

@@ -27,20 +27,14 @@ bool route_can_carry_even_disabled(const struct gossmap *map,
void *unused); void *unused);
/* Shortest path, with lower amount tiebreak */ /* Shortest path, with lower amount tiebreak */
bool route_path_shorter(u32 old_distance, u32 new_distance, u64 route_score_shorter(u32 distance,
struct amount_msat old_cost, struct amount_msat cost,
struct amount_msat new_cost, struct amount_msat risk);
struct amount_msat old_risk,
struct amount_msat new_risk,
void *unused);
/* Cheapest path, with shorter path tiebreak */ /* Cheapest path, with shorter path tiebreak */
bool route_path_cheaper(u32 old_distance, u32 new_distance, u64 route_score_cheaper(u32 distance,
struct amount_msat old_cost, struct amount_msat cost,
struct amount_msat new_cost, struct amount_msat risk);
struct amount_msat old_risk,
struct amount_msat new_risk,
void *unused);
/* Extract route tal_arr from completed dijkstra */ /* Extract route tal_arr from completed dijkstra */
struct route **route_from_dijkstra(const struct gossmap *map, struct route **route_from_dijkstra(const struct gossmap *map,

2
devtools/route.c
View File

@@ -52,7 +52,7 @@ static struct route **least_cost(struct gossmap *map,
tstart = time_mono(); tstart = time_mono();
dij = dijkstra(tmpctx, map, dst, dij = dijkstra(tmpctx, map, dst,
sent, riskfactor, route_can_carry, sent, riskfactor, route_can_carry,
route_path_cheaper, NULL); route_score_cheaper, NULL);
tstop = time_mono(); tstop = time_mono();
printf("# Time to find route: %"PRIu64" usec\n", printf("# Time to find route: %"PRIu64" usec\n",

6
devtools/topology.c
View File

@@ -55,7 +55,7 @@ static size_t count_possible_sources(const struct gossmap *map,
size_t distance_budget, num; size_t distance_budget, num;
dij = dijkstra(tmpctx, map, n, AMOUNT_MSAT(0), 0, dij = dijkstra(tmpctx, map, n, AMOUNT_MSAT(0), 0,
channel_usable_to_excl, route_path_shorter, exclude); channel_usable_to_excl, route_score_shorter, exclude);
if (is_last_node) if (is_last_node)
distance_budget = ROUTING_MAX_HOPS - 1; distance_budget = ROUTING_MAX_HOPS - 1;
@@ -132,7 +132,7 @@ static size_t count_possible_destinations(const struct gossmap *map,
size_t distance_budget, num; size_t distance_budget, num;
dij = dijkstra(tmpctx, map, start, AMOUNT_MSAT(0), 0, dij = dijkstra(tmpctx, map, start, AMOUNT_MSAT(0), 0,
channel_usable_from_excl, route_path_shorter, exclude); channel_usable_from_excl, route_score_shorter, exclude);
if (is_first_node) if (is_first_node)
distance_budget = ROUTING_MAX_HOPS - 1; distance_budget = ROUTING_MAX_HOPS - 1;
@@ -191,7 +191,7 @@ static bool measure_least_cost(struct gossmap *map,
tstart = time_mono(); tstart = time_mono();
dij = dijkstra(tmpctx, map, dst, dij = dijkstra(tmpctx, map, dst,
sent, riskfactor, channel_usable, sent, riskfactor, channel_usable,
route_path_cheaper, NULL); route_score_cheaper, NULL);
tstop = time_mono(); tstop = time_mono();
printf("# Time to find path: %"PRIu64" usec\n", printf("# Time to find path: %"PRIu64" usec\n",