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-rw-r--r--erts/emulator/beam/erl_bif_info.c20
-rw-r--r--erts/emulator/beam/erl_map.c27
2 files changed, 36 insertions, 11 deletions
diff --git a/erts/emulator/beam/erl_bif_info.c b/erts/emulator/beam/erl_bif_info.c
index d750e34be3..0774ab51af 100644
--- a/erts/emulator/beam/erl_bif_info.c
+++ b/erts/emulator/beam/erl_bif_info.c
@@ -3597,6 +3597,26 @@ BIF_RETTYPE erts_debug_get_internal_state_1(BIF_ALIST_1)
BIF_RET(erts_debug_reader_groups_map(BIF_P, (int) groups));
}
+ else if (ERTS_IS_ATOM_STR("internal_hash", tp[1])) {
+ Uint hash = (Uint) make_internal_hash(tp[2]);
+ Uint hsz = 0;
+ Eterm* hp;
+ erts_bld_uint(NULL, &hsz, hash);
+ hp = HAlloc(BIF_P,hsz);
+ return erts_bld_uint(&hp, NULL, hash);
+ }
+ else if (ERTS_IS_ATOM_STR("atom", tp[1])) {
+ Uint ix;
+ if (!term_to_Uint(tp[2], &ix))
+ BIF_ERROR(BIF_P, BADARG);
+ while (ix >= atom_table_size()) {
+ char tmp[20];
+ erts_snprintf(tmp, sizeof(tmp), "am%x", atom_table_size());
+ erts_atom_put((byte *) tmp, strlen(tmp), ERTS_ATOM_ENC_LATIN1, 1);
+ }
+ return make_atom(ix);
+ }
+
break;
}
default:
diff --git a/erts/emulator/beam/erl_map.c b/erts/emulator/beam/erl_map.c
index bd6da0a6f1..bcbda65da0 100644
--- a/erts/emulator/beam/erl_map.c
+++ b/erts/emulator/beam/erl_map.c
@@ -2549,19 +2549,24 @@ static int int_sqrt_ceiling(Uint x)
}
}
-Uint hashmap_over_estimated_heap_size(Uint n)
+Uint hashmap_over_estimated_heap_size(Uint k)
{
- /* n is nr of key-value pairs.
- Average nr of nodes is about n/3.
- Standard deviation is about sqrt(n)/3.
- Assuming normal probability distribution,
- we overestimate nr of nodes by 14 std.devs, which gives a probability
- for overrun of 1.0e-49 (same magnitude as a git SHA1 collision).
+ /* k is nr of key-value pairs.
+ N(k) is expected nr of nodes in hamt.
+
+ Observation:
+ For uniformly distributed hash values, average of N varies between
+ 0.3*k and 0.4*k (with a beautiful sine curve)
+ and standard deviation of N is about sqrt(k)/3.
+
+ Assuming normal probability distribution, we overestimate nr of nodes
+ by 15 std.devs above the average, which gives a probability for overrun
+ less than 1.0e-49 (same magnitude as a git SHA1 collision).
*/
- Uint nodes = (n + int_sqrt_ceiling(n)*14) / 3;
- return (n*2 + /* leaf cons cells */
- n + /* leaf list terms */
- nodes*2); /* headers + parent refs */
+ Uint max_nodes = 2*k/5 + (15/3)*int_sqrt_ceiling(k);
+ return (k*2 + /* leaf cons cells */
+ k + /* leaf list terms */
+ max_nodes*2); /* headers + parent boxed terms */
}