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Export of internal Abseil changes.

Browse source 
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00d42e3d5433aaf29c2ed293520b2ba178ae8bdb by Greg Falcon <gfalcon@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 238061818

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867a7ca318fac2991ea9a4107dbae3cc9fbf974a by Abseil Team <absl-team@google.com>:

Added a IWYU export pragma when including a standard header for the purpose of aliasing its symbols.

PiperOrigin-RevId: 238022277

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17047745058f2f151cd986ea9f649512542d3876 by Matt Armstrong <marmstrong@google.com>:

Clarify the comment discouraging WrapUnique<T>(x) calls.

PiperOrigin-RevId: 237873803

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3dcb2e4968243d33ca0ce53280c445df50f4a7ec by Samuel Benzaquen <sbenza@google.com>:

Workaround clang bug https://bugs.llvm.org/show_bug.cgi?id=38289

PiperOrigin-RevId: 237873551

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f348d2dc7087a990cbdfb95aa51fd7ff478ae40e by Samuel Benzaquen <sbenza@google.com>:

Reduce minimum capacity to 1.
This reduces memory usage for small tables.
A flat_hash_set<int> of 1 element goes from 92 bytes to 24.
A flat_hash_set<string> of 1 element goes from 512 bytes to 56.

PiperOrigin-RevId: 237859811

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9c8125be5e4e5d22a7bb62bdec8c323338385c1b by Jon Cohen <cohenjon@google.com>:

Bump to CMake 3.5. This is the oldest modern cmake being included by default in most popular OS distributions according to https://repology.org/project/cmake/versions.  Specifically, Ubuntu LTS 16.04 uses cmake 3.5 (https://packages.ubuntu.com/xenial/cmake)

PiperOrigin-RevId: 237859345

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07638d672e0a4dced986a62750cfd8318ed36ffa by Derek Mauro <dmauro@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 237714597
GitOrigin-RevId: 00d42e3d5433aaf29c2ed293520b2ba178ae8bdb
Change-Id: I5faecc45add4a5a774d4f9baf06e5519091f2ccc
This commit is contained in:
Abseil Team 2019-03-12 11:39:15 -07:00 • committed by vslashg
parent 88a152ae74
commit 256be56344
37 changed files with 180 additions and 128 deletions
Download patch file Download diff file Expand all files Collapse all files

46
absl/container/internal/raw_hash_set.h
View file

@ -446,9 +446,7 @@ using Group = GroupPortableImpl;
template <class Policy, class Hash, class Eq, class Alloc>
class raw_hash_set;
inline bool IsValidCapacity(size_t n) {
return ((n + 1) & n) == 0 && n >= Group::kWidth - 1;
}
inline bool IsValidCapacity(size_t n) { return ((n + 1) & n) == 0 && n > 0; }
// PRECONDITION:
// IsValidCapacity(capacity)
@ -470,13 +468,9 @@ inline void ConvertDeletedToEmptyAndFullToDeleted(
ctrl[capacity] = kSentinel;
}
// Rounds up the capacity to the next power of 2 minus 1 and ensures it is
// greater or equal to Group::kWidth - 1.
// Rounds up the capacity to the next power of 2 minus 1, with a minimum of 1.
inline size_t NormalizeCapacity(size_t n) {
constexpr size_t kMinCapacity = Group::kWidth - 1;
return n <= kMinCapacity
? kMinCapacity
: (std::numeric_limits<size_t>::max)() >> LeadingZeros(n);
return n ? ~size_t{} >> LeadingZeros(n) : 1;
}
// We use 7/8th as maximum load factor.
@ -1507,6 +1501,7 @@ class raw_hash_set {
void drop_deletes_without_resize() ABSL_ATTRIBUTE_NOINLINE {
assert(IsValidCapacity(capacity_));
assert(!is_small());
// Algorithm:
// - mark all DELETED slots as EMPTY
// - mark all FULL slots as DELETED
@ -1572,7 +1567,7 @@ class raw_hash_set {
void rehash_and_grow_if_necessary() {
if (capacity_ == 0) {
resize(Group::kWidth - 1);
resize(1);
} else if (size() <= CapacityToGrowth(capacity()) / 2) {
// Squash DELETED without growing if there is enough capacity.
drop_deletes_without_resize();
@ -1619,17 +1614,15 @@ class raw_hash_set {
auto mask = g.MatchEmptyOrDeleted();
if (mask) {
#if !defined(NDEBUG)
// We want to force small tables to have random entries too, so
// in debug build we will randomly insert in either the front or back of
// We want to add entropy even when ASLR is not enabled.
// In debug build we will randomly insert in either the front or back of
// the group.
// TODO(kfm,sbenza): revisit after we do unconditional mixing
if (ShouldInsertBackwards(hash, ctrl_))
if (!is_small() && ShouldInsertBackwards(hash, ctrl_)) {
return {seq.offset(mask.HighestBitSet()), seq.index()};
else
return {seq.offset(mask.LowestBitSet()), seq.index()};
#else
return {seq.offset(mask.LowestBitSet()), seq.index()};
}
#endif
return {seq.offset(mask.LowestBitSet()), seq.index()};
}
assert(seq.index() < capacity_ && "full table!");
seq.next();
@ -1732,11 +1725,28 @@ class raw_hash_set {
}
ctrl_[i] = h;
ctrl_[((i - Group::kWidth) & capacity_) + Group::kWidth] = h;
ctrl_[((i - Group::kWidth) & capacity_) + 1 +
((Group::kWidth - 1) & capacity_)] = h;
}
size_t& growth_left() { return settings_.template get<0>(); }
// The representation of the object has two modes:
// - small: For capacities < kWidth-1
// - large: For the rest.
//
// Differences:
// - In small mode we are able to use the whole capacity. The extra control
// bytes give us at least one "empty" control byte to stop the iteration.
// This is important to make 1 a valid capacity.
//
// - In small mode only the first `capacity()` control bytes after the
// sentinel are valid. The rest contain dummy kEmpty values that do not
// represent a real slot. This is important to take into account on
// find_first_non_full(), where we never try ShouldInsertBackwards() for
// small tables.
bool is_small() const { return capacity_ < Group::kWidth - 1; }
hasher& hash_ref() { return settings_.template get<1>(); }
const hasher& hash_ref() const { return settings_.template get<1>(); }
key_equal& eq_ref() { return settings_.template get<2>(); }