Introduce table improvement by Vladimir Makarov <vmakarov@redhat.com>.

[Feature #12142]
	See header of st.c for improvment details.

	You can see all of code history here:
	<https://github.com/vnmakarov/ruby/tree/hash_tables_with_open_addressing>

	This improvement is discussed at
	<https://bugs.ruby-lang.org/issues/12142>
	with many people, especially with Yura Sokolov.

	* st.c: improve st_table.

	* include/ruby/st.h: ditto.

	* internal.h, numeric.c, hash.c (rb_dbl_long_hash): extract a function.

	* ext/-test-/st/foreach/foreach.c: catch up this change.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56650 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

NEWS

@@ -324,3 +324,5 @@ with all sufficient information, see the ChangeLog file or Redmine
   to `Math.max(x, y)`.
 
 * Thread deadlock detection now shows their backtrace and dependency. [Feature #8214]
+
+* Table (st.c) internal data structure is improved. [Feature #12142]

ext/-test-/st/foreach/foreach.c

@@ -14,13 +14,13 @@ force_unpack_check(struct checker *c, st_data_t key, st_data_t val)
     if (c->nr == 0) {
 	st_data_t i;
 
-	if (!c->tbl->entries_packed) rb_bug("should be packed\n");
+	if (c->tbl->bins != NULL) rb_bug("should be packed\n");
 
 	/* force unpacking during iteration: */
 	for (i = 1; i < expect_size; i++)
 	    st_add_direct(c->tbl, i, i);
 
-	if (c->tbl->entries_packed) rb_bug("should be unpacked\n");
+	if (c->tbl->bins == NULL) rb_bug("should be unpacked\n");
     }
 
     if (key != c->nr) {
@@ -84,7 +84,7 @@ unp_fec(VALUE self, VALUE test)
 
     st_add_direct(tbl, 0, 0);
 
-    if (!tbl->entries_packed) rb_bug("should still be packed\n");
+    if (tbl->bins != NULL) rb_bug("should still be packed\n");
 
     st_foreach_check(tbl, unp_fec_i, (st_data_t)&c, -1);
 
@@ -98,7 +98,7 @@ unp_fec(VALUE self, VALUE test)
 		(VALUE)c.nr, (VALUE)expect_size);
     }
 
-    if (tbl->entries_packed) rb_bug("should be unpacked\n");
+    if (tbl->bins == NULL) rb_bug("should be unpacked\n");
 
     st_free_table(tbl);
 
@@ -145,7 +145,7 @@ unp_fe(VALUE self, VALUE test)
 
     st_add_direct(tbl, 0, 0);
 
-    if (!tbl->entries_packed) rb_bug("should still be packed\n");
+    if (tbl->bins != NULL) rb_bug("should still be packed\n");
 
     st_foreach(tbl, unp_fe_i, (st_data_t)&c);
 
@@ -159,7 +159,7 @@ unp_fe(VALUE self, VALUE test)
 		(VALUE)c.nr, (VALUE)expect_size);
     }
 
-    if (tbl->entries_packed) rb_bug("should be unpacked\n");
+    if (tbl->bins == NULL) rb_bug("should be unpacked\n");
 
     st_free_table(tbl);
 

hash.c

@@ -145,14 +145,36 @@ rb_hash(VALUE obj)
 
 long rb_objid_hash(st_index_t index);
 
-static st_index_t
-any_hash(VALUE a, st_index_t (*other_func)(VALUE))
+long
+rb_dbl_long_hash(double d)
+{
+    /* normalize -0.0 to 0.0 */
+    if (d == 0.0) d = 0.0;
+#if SIZEOF_INT == SIZEOF_VOIDP
+    return rb_memhash(&d, sizeof(d));
+#else
+    {
+	union {double d; uint64_t i;} u;
+
+	u.d = d;
+	return rb_objid_hash(u.i);
+    }
+#endif
+}
+
+#if SIZEOF_INT == SIZEOF_VOIDP
+static const st_index_t str_seed = 0xfa835867;
+#else
+static const st_index_t str_seed = 0xc42b5e2e6480b23bULL;
+#endif
+
+static inline st_index_t
+any_hash_general(VALUE a, int strong_p, st_index_t (*other_func)(VALUE))
 {
     VALUE hval;
     st_index_t hnum;
 
     if (SPECIAL_CONST_P(a)) {
-	if (a == Qundef) return 0;
 	if (STATIC_SYM_P(a)) {
 	    hnum = a >> (RUBY_SPECIAL_SHIFT + ID_SCOPE_SHIFT);
 	    goto out;
@@ -164,7 +186,9 @@ any_hash(VALUE a, st_index_t (*other_func)(VALUE))
 	hnum = rb_objid_hash((st_index_t)a);
     }
     else if (BUILTIN_TYPE(a) == T_STRING) {
-	hnum = rb_str_hash(a);
+	hnum = (strong_p
+		? rb_str_hash(a)
+		: st_hash(RSTRING_PTR(a), RSTRING_LEN(a), str_seed));
     }
     else if (BUILTIN_TYPE(a) == T_SYMBOL) {
 	hnum = RSYMBOL(a)->hashval;
@@ -175,8 +199,7 @@ any_hash(VALUE a, st_index_t (*other_func)(VALUE))
     }
     else if (BUILTIN_TYPE(a) == T_FLOAT) {
       flt:
-	hval = rb_dbl_hash(rb_float_value(a));
-	hnum = FIX2LONG(hval);
+	hnum = rb_dbl_long_hash(rb_float_value(a));
     }
     else {
 	hnum = other_func(a);
@@ -193,40 +216,62 @@ obj_any_hash(VALUE obj)
     return FIX2LONG(obj);
 }
 
-static st_index_t
-rb_any_hash(VALUE a)
-{
-    return any_hash(a, obj_any_hash);
+static inline st_index_t
+any_hash_weak(VALUE a, st_index_t (*other_func)(VALUE)) {
+    return any_hash_general(a, FALSE, other_func);
 }
 
 static st_index_t
-rb_num_hash_start(st_index_t n)
+rb_any_hash_weak(VALUE a) {
+    return any_hash_weak(a, obj_any_hash);
+}
+
+static inline st_index_t
+any_hash(VALUE a, st_index_t (*other_func)(VALUE)) {
+    return any_hash_general(a, TRUE, other_func);
+}
+
+static st_index_t
+rb_any_hash(VALUE a) {
+    return any_hash(a, obj_any_hash);
+}
+
+/* Here is a hash function for 64-bit key.  It is about 5 times faster
+   (2 times faster when uint128 type is absent) on Haswell than
+   tailored Spooky or City hash function can be.  */
+
+/* Here we two primes with random bit generation.  */
+static const uint64_t prime1 = 0x2e0bb864e9ea7df5ULL;
+static const uint64_t prime2 = 0xcdb32970830fcaa1ULL;
+
+
+static inline uint64_t
+mult_and_mix (uint64_t m1, uint64_t m2)
 {
-    /*
-     * This hash function is lightly-tuned for Ruby.  Further tuning
-     * should be possible.  Notes:
-     *
-     * - (n >> 3) alone is great for heap objects and OK for fixnum,
-     *   however symbols perform poorly.
-     * - (n >> (RUBY_SPECIAL_SHIFT+3)) was added to make symbols hash well,
-     *   n.b.: +3 to remove most ID scope, +1 worked well initially, too
-     *   n.b.: +1 (instead of 3) worked well initially, too
-     * - (n << 16) was finally added to avoid losing bits for fixnums
-     * - avoid expensive modulo instructions, it is currently only
-     *   shifts and bitmask operations.
-     */
-    return (n >> (RUBY_SPECIAL_SHIFT + 3) ^ (n << 16)) ^ (n >> 3);
+#if defined(__GNUC__) && UINT_MAX != ULONG_MAX
+    __uint128_t r = (__uint128_t) m1 * (__uint128_t) m2;
+    return (uint64_t) (r >> 64) ^ (uint64_t) r;
+#else
+    uint64_t hm1 = m1 >> 32, hm2 = m2 >> 32;
+    uint64_t lm1 = m1, lm2 = m2;
+    uint64_t v64_128 = hm1 * hm2;
+    uint64_t v32_96 = hm1 * lm2 + lm1 * hm2;
+    uint64_t v1_32 = lm1 * lm2;
+
+    return (v64_128 + (v32_96 >> 32)) ^ ((v32_96 << 32) + v1_32);
+#endif
+}
+
+static inline uint64_t
+key64_hash (uint64_t key, uint32_t seed)
+{
+    return mult_and_mix(key + seed, prime1);
 }
 
 long
 rb_objid_hash(st_index_t index)
 {
-    st_index_t hnum = rb_num_hash_start(index);
-
-    hnum = rb_hash_start(hnum);
-    hnum = rb_hash_uint(hnum, (st_index_t)rb_any_hash);
-    hnum = rb_hash_end(hnum);
-    return hnum;
+    return key64_hash(index, (uint32_t) prime2);
 }
 
 static st_index_t
@@ -250,6 +295,7 @@ rb_hash_iter_lev(VALUE h)
 
 static const struct st_hash_type objhash = {
     rb_any_cmp,
+    rb_any_hash_weak,
     rb_any_hash,
 };
 
@@ -269,7 +315,7 @@ rb_ident_hash(st_data_t n)
     }
 #endif
 
-    return (st_index_t)rb_num_hash_start((st_index_t)n);
+    return (st_index_t) key64_hash((st_index_t)n, (uint32_t) prime2);
 }
 
 static const struct st_hash_type identhash = {

include/ruby/st.h

@@ -1,6 +1,8 @@
-/* This is a public domain general purpose hash table package written by Peter Moore @ UCB. */
+/* This is a public domain general purpose hash table package
+   originally written by Peter Moore @ UCB.
 
-/* @(#) st.h 5.1 89/12/14 */
+   The hash table data strutures were redesigned and the package was
+   rewritten by Vladimir Makarov <vmakarov@redhat.com>.  */
 
 #ifndef RUBY_ST_H
 #define RUBY_ST_H 1
@@ -46,6 +48,10 @@ typedef unsigned LONG_LONG st_data_t;
 typedef struct st_table st_table;
 
 typedef st_data_t st_index_t;
+
+/* Maximal value of unsigned integer type st_index_t.  */
+#define MAX_ST_INDEX_VAL (~(st_index_t) 0)
+
 typedef int st_compare_func(st_data_t, st_data_t);
 typedef st_index_t st_hash_func(st_data_t);
 
@@ -55,10 +61,13 @@ typedef char st_check_for_sizeof_st_index_t[SIZEOF_VOIDP == (int)sizeof(st_index
 struct st_hash_type {
     int (*compare)(ANYARGS /*st_data_t, st_data_t*/); /* st_compare_func* */
     st_index_t (*hash)(ANYARGS /*st_data_t*/);        /* st_hash_func* */
+    /* The following is an optional func for stronger hash.  When we
+       have many different keys with the same hash we can switch to
+       use it to prevent a denial attack with usage of hash table
+       collisions. */
+    st_index_t (*strong_hash)(ANYARGS /*st_data_t*/);
 };
 
-#define ST_INDEX_BITS (sizeof(st_index_t) * CHAR_BIT)
-
 #if defined(HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR) && defined(HAVE_BUILTIN___BUILTIN_TYPES_COMPATIBLE_P)
 # define ST_DATA_COMPATIBLE_P(type) \
    __builtin_choose_expr(__builtin_types_compatible_p(type, st_data_t), 1, 0)
@@ -66,33 +75,30 @@ struct st_hash_type {
 # define ST_DATA_COMPATIBLE_P(type) 0
 #endif
 
+typedef struct st_table_entry st_table_entry;
+
+struct st_table_entry; /* defined in st.c */
+
 struct st_table {
+    /* Cached features of the table -- see st.c for more details.  */
+    unsigned char entry_power, bin_power, size_ind;
+    /* True when we are rebuilding the table.  */
+    unsigned char inside_rebuild_p;
+    /* How many times the table was rebuilt.  */
+    unsigned int rebuilds_num;
+    /* Currently used hash function.  */
+    st_index_t (*curr_hash)(ANYARGS /*st_data_t*/);
     const struct st_hash_type *type;
-    st_index_t num_bins;
-    unsigned int entries_packed : 1;
-#ifdef __GNUC__
-    /*
-     * C spec says,
-     *   A bit-field shall have a type that is a qualified or unqualified
-     *   version of _Bool, signed int, unsigned int, or some other
-     *   implementation-defined type. It is implementation-defined whether
-     *   atomic types are permitted.
-     * In short, long and long long bit-field are implementation-defined
-     * feature. Therefore we want to suppress a warning explicitly.
-     */
-    __extension__
-#endif
-    st_index_t num_entries : ST_INDEX_BITS - 1;
-    union {
-	struct {
-	    struct st_table_entry **bins;
-	    void *private_list_head[2];
-	} big;
-	struct {
-	    struct st_packed_entry *entries;
-	    st_index_t real_entries;
-	} packed;
-    } as;
+    /* Number of entries currently in the table.  */
+    st_index_t num_entries;
+    /* Array of bins used for access by keys.  */
+    st_index_t *bins;
+    /* Start and bound index of entries in array entries.
+       entries_starts and entries_bound are in interval
+       [0,allocated_entries].  */
+    st_index_t entries_start, entries_bound;
+    /* Array of size 2^entry_power.  */
+    st_table_entry *entries;
 };
 
 #define st_is_member(table,key) st_lookup((table),(key),(st_data_t *)0)
@@ -121,7 +127,6 @@ typedef int st_update_callback_func(st_data_t *key, st_data_t *value, st_data_t
 int st_update(st_table *table, st_data_t key, st_update_callback_func *func, st_data_t arg);
 int st_foreach(st_table *, int (*)(ANYARGS), st_data_t);
 int st_foreach_check(st_table *, int (*)(ANYARGS), st_data_t, st_data_t);
-int st_reverse_foreach(st_table *, int (*)(ANYARGS), st_data_t);
 st_index_t st_keys(st_table *table, st_data_t *keys, st_index_t size);
 st_index_t st_keys_check(st_table *table, st_data_t *keys, st_index_t size, st_data_t never);
 st_index_t st_values(st_table *table, st_data_t *values, st_index_t size);

internal.h

@@ -1085,6 +1085,7 @@ VALUE rb_hash_has_key(VALUE hash, VALUE key);
 VALUE rb_hash_default_value(VALUE hash, VALUE key);
 VALUE rb_hash_set_default_proc(VALUE hash, VALUE proc);
 long rb_objid_hash(st_index_t index);
+long rb_dbl_long_hash(double d);
 st_table *rb_init_identtable(void);
 st_table *rb_init_identtable_with_size(st_index_t size);
 

numeric.c

@@ -1421,12 +1421,7 @@ flo_hash(VALUE num)
 VALUE
 rb_dbl_hash(double d)
 {
-    st_index_t hash;
-
-    /* normalize -0.0 to 0.0 */
-    if (d == 0.0) d = 0.0;
-    hash = rb_memhash(&d, sizeof(d));
-    return ST2FIX(hash);
+    return LONG2FIX(rb_dbl_long_hash (d));
 }
 
 VALUE