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Merge branch 'optimize_g_double_hash' into 'main'

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Optimize the implementation of `g_double_hash`

See merge request GNOME/glib!2924
This commit is contained in:
Marco Trevisan
2022-10-11 11:26:41 +00:00
parent db259b5925 e02db8ea22
commit 4231426abe
2 changed files with 38 additions and 2 deletions
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4
glib/ghash.c
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@@ -2490,7 +2490,7 @@ g_int64_equal (gconstpointer v1,
guint
g_int64_hash (gconstpointer v)
{
return (guint) *(const gint64*) v;
return (guint) ((const guint) (*(guint64 *) v >> 32)) ^ (*(const guint *) v);
}
/**
@@ -2531,5 +2531,5 @@ g_double_equal (gconstpointer v1,
guint
g_double_hash (gconstpointer v)
{
return (guint) *(const gdouble*) v;
return (guint) ((const guint) (*(guint64 *) v >> 32)) ^ (*(const guint *) v);
}

36
glib/tests/hash.c
View File

@@ -459,6 +459,19 @@ int64_hash_test (void)
g_hash_table_destroy (h);
}
static void
int64_hash_collision_test (void)
{
gint64 m;
gint64 n;
g_test_summary ("Check int64 Hash collisions caused by ignoring high word");
m = 722;
n = ((gint64) 2003 << 32) + 722;
g_assert_cmpuint (g_int64_hash (&m), !=, g_int64_hash (&n));
}
static void
double_hash_test (void)
{
@@ -488,6 +501,27 @@ double_hash_test (void)
g_hash_table_destroy (h);
}
static void
double_hash_collision_test (void)
{
gdouble m;
gdouble n;
g_test_summary ("Check double Hash collisions caused by int conversion " \
"and by numbers larger than 2^64-1 (G_MAXUINT64)");
g_test_bug ("https://gitlab.gnome.org/GNOME/glib/-/issues/2771");
/* Equal when directly converted to integers */
m = 0.1;
n = 0.2;
g_assert_cmpuint (g_double_hash (&m), !=, g_double_hash (&n));
/* Numbers larger than 2^64-1 (G_MAXUINT64) */
m = 1e100;
n = 1e200;
g_assert_cmpuint (g_double_hash (&m), !=, g_double_hash (&n));
}
static void
string_free (gpointer data)
{
@@ -1715,7 +1749,9 @@ main (int argc, char *argv[])
g_test_add_func ("/hash/direct2", direct_hash_test2);
g_test_add_func ("/hash/int", int_hash_test);
g_test_add_func ("/hash/int64", int64_hash_test);
g_test_add_func ("/hash/int64/collisions", int64_hash_collision_test);
g_test_add_func ("/hash/double", double_hash_test);
g_test_add_func ("/hash/double/collisions", double_hash_collision_test);
g_test_add_func ("/hash/string", string_hash_test);
g_test_add_func ("/hash/set", set_hash_test);
g_test_add_func ("/hash/set-ref", set_ref_hash_test);