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open hash: use open addressing with linear probing (WIP)
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and a layout similar to array_he, inlined 1-2 word hash array.

variants to try: simple linear, double, quadratic, robin-hood, hopscotch.
khash tried double hashing and found it slower. robin-hood with
backward deletion propagation would be an alternative, but first
we need to re-architecture and abstract the various probing implementations
and search loops scattered all over.

See GH #24
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@rurban
Reini Urban authored and rurban committed Apr 5, 2019
1 parent 5f26c0a commit a2ab02b
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Showing 8 changed files with 208 additions and 1,279 deletions.
13 changes: 7 additions & 6 deletions dump.c
View file
Expand Up @@ -804,7 +804,7 @@ Perl_dump_packsubs_perl(pTHX_ const HV *stash, bool justperl)
return;
for (i = 0; i <= HvMAX(stash); i++) {
const HE *entry = AHe(HvARRAY(stash)[i]);
HE_EACH(hv, entry, {
HE_EACH(stash, i, entry, {
GV * gv = (GV *)HeVAL(entry);
if (SvROK(gv) && SvTYPE(SvRV(gv)) == SVt_PVCV)
/* unfake a fake GV */
Expand Down Expand Up @@ -2486,7 +2486,7 @@ Perl_do_sv_dump(pTHX_ I32 level, PerlIO *file, SV *sv, I32 nest, I32 maxnest,
for (i = 0; i <= HvMAX(sv); i++) {
HE* h = AHe(HvARRAY(sv)[i]);
U32 count = 0;
HE_EACH(sv, h, count++);
HE_EACH(sv, i, h, count++);
if (count > FREQ_MAX)
count = FREQ_MAX;
freq[count]++;
Expand Down Expand Up @@ -2682,14 +2682,15 @@ Perl_do_sv_dump(pTHX_ I32 level, PerlIO *file, SV *sv, I32 nest, I32 maxnest,
}
if (nest < maxnest) {
HV * const hv = MUTABLE_HV(sv);

if (HvARRAY(hv)) {
HE *he;
U32 i;
U32 count = 0;
U32 maxcount = maxnest - nest;
for (i=0; i <= HvMAX(hv); i++) {
he = AHe(HvARRAY(hv)[i]);
HE_EACH(hv, he, {
HE *he = AHe(HvARRAY(hv)[i]);
HE_EACH(hv, i, he, {
U32 hash;
SV * keysv;
SV * elt;
Expand Down Expand Up @@ -3313,7 +3314,7 @@ Perl_deb_hechain(pTHX_ HE* entry)
assert(HeHASH(entry));
assert(entry != HeNEXT(entry));
assert(i <= PERL_ARENA_SIZE/sizeof(HE));
})
}
PerlIO_printf(Perl_debug_log, " )\n");
}
#endif
Expand Down Expand Up @@ -3997,7 +3998,7 @@ S__hv_dump(pTHX_ SV* sv, bool with_values, int level)
for (i = 0; i <= HvMAX(sv); i++) {
HE* h = AHe(ents[i]);
PerlIO_printf(file, "[%u]: ", (unsigned)i);
HE_EACH(sv, h, {
HE_EACH(sv, i, h, {
#if defined(PERL_INLINE_HASH) && defined(DEBUGGING)
if (!ents[i].hent_hash) continue;
#endif
Expand Down
2 changes: 1 addition & 1 deletion gv.c
View file
Expand Up @@ -2638,7 +2638,7 @@ Perl_gv_check(pTHX_ HV *stash)
/* mark stash is being scanned, to avoid recursing */
HvAUX(stash)->xhv_aux_flags |= HvAUXf_SCAN_STASH;

HE_EACH(stash, entry, {
HE_EACH(stash, i, entry, {
GV *gv;
HV *hv;
STRLEN keylen = HeKLEN(entry);
Expand Down
113 changes: 53 additions & 60 deletions hv.c
View file
Expand Up @@ -2,28 +2,26 @@
*
* Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
* 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 by Larry Wall and others
* Copyright (C) 2016 cPanel Inc.
*
* You may distribute under the terms of either the GNU General Public
* License or the Artistic License, as specified in the README file.
*
*/

/*
* I sit beside the fire and think
* of all that I have seen.
* --Bilbo
*
* [p.278 of _The Lord of the Rings_, II/iii: "The Ring Goes South"]
*/

/*
=head1 Hash Manipulation Functions
A HV structure represents a Perl hash. It consists mainly of an array
of pointers, each of which points to a linked list of HE structures. The
array is indexed by the hash function of the key, so each linked list
represents all the hash entries with the same hash value. Each HE contains
a pointer to the actual value, plus a pointer to a HEK structure which
holds the key and hash value.
A HV structure represents a Perl hash. It consists mainly of an array
of hash entries (HE). The array is indexed by the hash function of
the key.
It is now an open addressing hash table with linear probing and
each entry contains a HE* ptr and the HASH value for faster inline
comparison. The AUX struct is allocated seperately, at [HvMAX].
The fill rate (load factor) went from 100% in perl5 and 90% in cperl
to now 70%.
=cut
Expand All @@ -34,9 +32,9 @@ holds the key and hash value.
#define PERL_HASH_INTERNAL_ACCESS
#include "perl.h"

/* New 90% fill rate ("load factor"). Was 100 before */
/* 70% fill rate ("load factor") with open addressing */
#ifndef HV_FILL_RATE
# define HV_FILL_RATE 90
# define HV_FILL_RATE 70
#endif
#ifndef HV_FILL_THRESHOLD
# define HV_FILL_THRESHOLD 31
Expand All @@ -45,16 +43,9 @@ holds the key and hash value.
#if HV_FILL_RATE == 100
# define DO_HSPLIT(xhv) ((xhv)->xhv_keys >= (xhv)->xhv_max)
#else
# define DO_HSPLIT_slow(xhv) !(xhv)->xhv_max || \
((U32)(((xhv)->xhv_keys * 100) / (xhv)->xhv_max) >= HV_FILL_RATE)
/* x/128 == x>>7, x>>ctz(n) */
# define DO_HSPLIT_fast(xhv) !(xhv)->xhv_max || \
# define DO_HSPLIT(xhv) !(xhv)->xhv_max || \
((U32)(((xhv)->xhv_keys * 100) >> CTZ(1+((xhv)->xhv_max))) >= HV_FILL_RATE)
# if 0
# define DO_HSPLIT(xhv) DO_HSPLIT_slow(xhv)
# else
# define DO_HSPLIT(xhv) DO_HSPLIT_fast(xhv)
# endif
#endif

static const char S_strtab_error[]
Expand Down Expand Up @@ -266,20 +257,20 @@ negative the key is assumed to be in UTF-8-encoded Unicode. The
C<hash> parameter is the precomputed hash value; if it is zero then
Perl will compute it.
The return value will be
C<NULL> if the operation failed or if the value did not need to be actually
stored within the hash (as in the case of tied hashes). Otherwise it can
be dereferenced to get the original C<SV*>. Note that the caller is
responsible for suitably incrementing the reference count of C<val> before
the call, and decrementing it if the function returned C<NULL>. Effectively
a successful C<hv_store> takes ownership of one reference to C<val>. This is
usually what you want; a newly created SV has a reference count of one, so
if all your code does is create SVs then store them in a hash, C<hv_store>
will own the only reference to the new SV, and your code doesn't need to do
anything further to tidy up. C<hv_store> is not implemented as a call to
C<hv_store_ent>, and does not create a temporary SV for the key, so if your
key data is not already in SV form then use C<hv_store> in preference to
C<hv_store_ent>.
The return value will be C<NULL> if the operation failed or if the
value did not need to be actually stored within the hash (as in the
case of tied hashes). Otherwise it can be dereferenced to get the
original C<SV*>. Note that the caller is responsible for suitably
incrementing the reference count of C<val> before the call, and
decrementing it if the function returned C<NULL>. Effectively a
successful C<hv_store> takes ownership of one reference to C<val>.
This is usually what you want; a newly created SV has a reference
count of one, so if all your code does is create SVs then store them
in a hash, C<hv_store> will own the only reference to the new SV, and
your code doesn't need to do anything further to tidy up. C<hv_store>
is not implemented as a call to C<hv_store_ent>, and does not create a
temporary SV for the key, so if your key data is not already in SV
form then use C<hv_store> in preference to C<hv_store_ent>.
See L<perlguts/"Understanding the Magic of Tied Hashes and Arrays"> for more
information on how to use this function on tied hashes.
Expand Down Expand Up @@ -406,9 +397,11 @@ static void
S_assert_hechain(pTHX_ HE* entry)
{
if (!entry) return;
HE_EACH(hv, entry,
#ifndef HASH_OPEN_LINEAR
HE_EACH(hv, i, entry,
assert(entry->hent_hek)
)
#endif
}

static void
Expand All @@ -417,7 +410,9 @@ S_assert_ahe(pTHX_ AHE* ahe)
#ifdef PERL_INLINE_HASH
assert(ahe->hent_he ? ahe->hent_hash : !ahe->hent_hash);
#endif
#ifndef HASH_OPEN_LINEAR
S_assert_hechain(aTHX_ ahe->hent_he);
#endif
}

#endif
Expand Down Expand Up @@ -649,7 +644,7 @@ Perl_hv_common(pTHX_ HV *hv, SV *keysv, const char *key, I32 klen,
*/
int keysv_flags = HEK_FLAGS(keysv_hek);
HE *orig_entry = entry;
HE_EACH(hv, entry, {
HE_EACH(hv, hindex, entry, {
const HEK *hek = HeKEY_hek(entry);
CHECK_HASH_FLOOD(collisions)
if (hek == keysv_hek)
Expand All @@ -665,7 +660,7 @@ Perl_hv_common(pTHX_ HV *hv, SV *keysv, const char *key, I32 klen,
entry = orig_entry;
}

HE_EACH(hv, entry, {
HE_EACH(hv, hindex, entry, {
CHECK_HASH_FLOOD(collisions)
if (HeHASH(entry) != hash) /* strings can't be equal */
continue;
Expand Down Expand Up @@ -754,7 +749,7 @@ Perl_hv_common(pTHX_ HV *hv, SV *keysv, const char *key, I32 klen,
/* move found bucket to the front
oe -> e -> A => e -> oe -> A
oe -> A .. X -> e -> B => e -> oe -> A .. X -> B */
if (entry != oentry->hent_he && !HvEITER_get(hv)) {
if (!HvEITER_get(hv) && entry != oentry->hent_he) {
if (HeNEXT(oentry->hent_he) == entry) {
DEBUG_H(PerlIO_printf(Perl_debug_log, "HASH move up 1\t%s{%s}\n",
HvNAME_get(hv)?HvNAME_get(hv):"", key));
Expand Down Expand Up @@ -1551,7 +1546,7 @@ S_hv_delete_common(pTHX_ HV *hv, SV *keysv, const char *key, I32 klen,
goto not_found;
#ifdef PERL_INLINE_HASH
if (first_entry->hent_hash != hash) {
oentry = &entry->hent_next;
oentry = &HeNEXT(entry);
entry = *oentry;
if (!entry)
goto not_found;
Expand All @@ -1572,7 +1567,7 @@ S_hv_delete_common(pTHX_ HV *hv, SV *keysv, const char *key, I32 klen,
*/
int keysv_flags = HEK_FLAGS(keysv_hek);

HE_OEACH(hv, oentry, entry, {
HE_OEACH(hv, hindex, oentry, entry, {
const HEK *hek = HeKEY_hek(entry);
CHECK_HASH_FLOOD(collisions)
if (hek == keysv_hek)
Expand Down Expand Up @@ -1969,7 +1964,7 @@ S_hsplit(pTHX_ HV *hv, U32 const oldsize, U32 newsize)
}
#endif
entry = *oentry;
}
}
}
if (UNLIKELY(newsize < oldsize)) { /* shrinked */
if (do_aux) /* move to left */
Expand Down Expand Up @@ -2101,16 +2096,17 @@ Perl_newHVhv(pTHX_ HV *ohv)
ents = (AHE*)a;

Copy(oents, ents, hv_max+1, AHE);
/* and descent into each bucket... */
for (; oent <= last; oent++, ents++) {
HE *e = oent->hent_he;
HE *prev = NULL;
/* In each bucket... */
for (i = 0; i <= hv_max; i++) {
HE *prev = NULL;
HE *oent = oents[i];

if (!oent->hent_he)
continue;
/* Copy the linked list of entries. */
HE_EACH(hv, e, {
const HEK *hek = HeKEY_hek(e);
e = oent->hent_he;
HE_EACH(hv, i, oent, {
const HEK *hek = HeKEY_hek(oent);
HE * const ent = new_HE();
SV * const val = HeVAL(e);

Expand Down Expand Up @@ -2307,7 +2303,7 @@ Perl_hv_clear(pTHX_ HV *hv)
U32 i;
for (i = 0; i <= xhv->xhv_max; i++) {
HE *entry = AHe(HvARRAY(hv)[i]);
HE_EACH(hv, entry, {
HE_EACH(hv, hindex, entry, {
/* not already placeholder */
if (!(He_IS_PLACEHOLDER(entry))) {
if (HeVAL(entry)) {
Expand Down Expand Up @@ -2509,10 +2505,7 @@ Perl_hfree_next_entry(pTHX_ HV *hv, U32 *indexp)
#endif
}
AHe(array[*indexp]) = HeNEXT(entry);
/*AHeHASH_set(&array[*indexp], HeNEXT(entry) ? HeHASH(HeNEXT(entry)) : 0);*/
#ifdef PERL_INLINE_HASH
array[*indexp].hent_hash = HeNEXT(entry) ? HeHASH(HeNEXT(entry)) : 0;
#endif
AHeHASH_set(&array[*indexp], HeNEXT(entry) ? HeHASH(HeNEXT(entry)) : 0);
((XPVHV*) SvANY(hv))->xhv_keys--;

if ( PL_phase != PERL_PHASE_DESTRUCT && HvENAME(hv)
Expand Down Expand Up @@ -3757,7 +3750,7 @@ S_share_hek_flags(pTHX_ const char *str, I32 len, U32 hash, int flags)
if (!entry)
goto not_found;

HE_EACH(hv, entry, {
HE_EACH(hv, hindex, entry, {
const HEK *hek = HeKEY_hek(entry);
CHECK_HASH_FLOOD(collisions)
if (HEK_HASH(hek) != hash) /* strings can't be equal */
Expand All @@ -3769,7 +3762,7 @@ S_share_hek_flags(pTHX_ const char *str, I32 len, U32 hash, int flags)
if (HEK_FLAGS(hek) != flags_masked)
continue;
break;
})
})

if (!entry)
not_found: {
Expand Down Expand Up @@ -3988,7 +3981,7 @@ Perl_refcounted_he_chain_2hv(pTHX_ const struct refcounted_he *chain, U32 flags)
SV *value;

#ifdef USE_ITHREADS
HE_EACH(hv, entry, {
HE_EACH(hv, hindex, entry, {
if (HeHASH(entry) == hash) {
/* We might have a duplicate key here. If so, entry is older
than the key we've already put in the hash, so if they are
Expand All @@ -4004,7 +3997,7 @@ Perl_refcounted_he_chain_2hv(pTHX_ const struct refcounted_he *chain, U32 flags)
CHECK_HASH_FLOOD(collisions)
})
#else
HE_EACH(hv, entry, {
HE_EACH(hv, hindex, entry, {
if (HeHASH(entry) == hash) {
/* We might have a duplicate key here. If so, entry is older
than the key we've already put in the hash, so if they are
Expand Down

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