cds / News: Recent posts

Maintenance release
- Added: apply( Func f ) method to containers based on flat combining.
  This method allows to execute any function over underlying container
  in exclusive mode.
- Removed: -fno-strict-aliasing requirement
- Fixed: a serious bug in WeakRingBuffer::front()
- Fixed: memcpy bug in CuckooHash with store_hash feature

Maintenance release
- issue #81: bug in gc::DHP when extending thread's retired array, thanks to gtroxler (https://github.com/gtroxler)
- Improved CMake scripts for simplifying libcds intergration with other projects:

 find_package(LibCDS)
 add_library(mylib INTERFACE)
 target_link_libraries(mylib INTERFACE LibCDS::cds)

Thansk to Louis Dionne (https://github.com/ldionne)

• Changed: cds::gc::HP is totally refactored:
  • simplified internal structures;
  • added ability to specify an external allocator for internal data;
  • external API for gc::HP is slightly changed: now scan type
    cannot be changed on the fly; it can be specified only in
    construction time.
• Changed: cds::gc::DHP is totally refactored to overcome some internal
  limitations. Now gc::DHP is fully adaptive variant of Hazard Pointer
  SMR, any dependencies on count of thread are removed, count of retired
  data and hazard pointers per thread are increased automaticaly by perforce.
  External API of gc::DHP class is changed: now only initial count
  of hazard pointers can be specified in the constructor. Like new gc::HP,
  the new gc::DHP supports an external allocator.
• Changed: exception handling. Now, exceptions raise by invoking new
  cds::throw_exception() function. If you compile your code with exception disabled,
  the function prints an exception message to stdout and calls abort()
  instead of throwing.
• Flat Combining: fixed memory-order bug that can lead to crash on weak ordered
  architecture like PowerPC or ARM
• Added: erase_at( iterator ) function to MichaelHashSet/Map and SplitListSet/Map
  based on IterableList
• Fixed a bug in BronsonAVLTreeMap::extract_min()/extract_max()/clear().
• Removed: signal-handled threaded uRCU (cds::urcu::signal_threaded) due
  bad performance
• Added more flat-combining queue tests, thanks to Marsel Galimullin.
• Changed cmake scripts to support MacOS and ARMv7/ARMv8 (64 bit),
  thanks to Michail Komarov (https://github.com/Nemo1369)
• Stress tests: removed command line parameter --detail-level and
  envvar CDSTEST_DETAIL_LEVEL for reducing compile time and executable size.
  To make full testset compile libcds with -DCDS_STRESS_TEST_LEVEL=N where
  N is 1 or 2.
• Changed: refactoring cds::backoff::exponential and cds::backoff::delay
  back-off strategies to avoid static data members in template classes.
• The library is extensively tested on x86-64, PowerPC and AArch64,
  thanks to GCC Compile Farm project

• Changed: CMake is used for build libcds. Ancient build.sh has been removed
• Changed: unit and stress tests are migrated to googletest framework
• Added: IterableList - an implementation of ordered list with thread-safe iterator. MichaelSet/Map and SplitListSet/Map support this type of ordered list and thread-safe iterable too.
• Added: wait strategies for flat combining technique. Based on research by Marsel Galimullin and Nikolai Rapotkin.
• Fixed: SkipList erase() and find() bugs that cause to infinite loop or to program crash in rare case.
• Fixed: serious bug in MichaelSet::emplace() function. New node was created twice from the arguments by move semantics. However, move semantics may change internal state of the argument that can lead to an incorrect element and even an incorrect key that breaks the set logic.
• Fixed: bug in FeldmanHashSet::erase_at( iterator ): due an error in precondition checking the function may incorrectly return false.
• Fixed: possible double-free case in flat combining algorithm. Thanks to Amila Jayasekara who pointed me to this problem
• Changed: cds::opt::buffer option is divided to initialized (cds::opt:✌️:initialized_dynamic_buffer, cds::opt:✌️:initialized_static_buffer) and uninitialized (cds::opt:✌️:uninitialized_dynamic_buffer,
  cds::opt:✌️:uninitialized_static_buffer) ones. The old cds::opt:✌️:dynamic_buffer and cds::opt:✌️:static_buffer classes are removed.
• Removed: TsigasCysleQueue (due undecidable ABA-problem)
• Removed: Michael's allocator cds/memory/michael/allocator.h
• Fixed: use-after-free bug in VyukovMPMCCycleQueue internal buffer. To prevent this bug the queue uses an uninitialized buffer now.
• Fixed: rare priority inversion bug in MSPriorityQueue
• Added: for minimizing runtime of stress test the detail level for some test is added. Command line argument --detail-level=N specifies what test should be ran: each test with level not greater than N will be ran. Instead of command line arg the enviromnent variable CDSTEST_DETAIL_LEVEL=N may be used. By default, the detail level is 0 that means only limited set of the test will be ran.

• Added: FeldmanHashSet/Map - an interesting hash map algorithm based on multi-level array, requires perfect hashing or fixed-sized keys. Supports thread-safe bidirectional iterators.
• Added: BronsonAVLTreeMap - Bronson's et al AVL tree implementation
• Added: CMake build script, thanks to Eugeny Kalishenko
• Changed: SplitList performance improving, thanks to Mike Krinkin
• Changed: semantic of member functions extract(), get() and its variants for MichaelList RCU-based specialization: extract() does not require RCU locking, get() now returns special wrapper object of type raw_ptr, see doc. Thus, semantics of extract()/get() of all RCU-based set and maps based on MichaelList (MichaelSet/Map, SplitListSet/Map) has been changed too.
• Changed: SplitListSet/Map functions get() and get_with() return special wrapper object of type raw_ptr, see doc.
• Removed: SplitListSet/Map force_dispose() function.
• cds::lock namespace is renamed to cds::sync. All classes defined in cds::lock namespace are moved to cds::sync with new names (for example, cds:🔒:SpinLock is renamed to cds::sync::spin_lock). cds::lock namespace and its contents is deprecated, it is kept for backward compatibility.
• The library has been checked by ThreadSanitizer, a lot of bugs has been fixed
• Added support for clang 3.7 with libc++

• the library has been rewritten to support at least C++11. Compilers: GCC 4.8+, clang 3.3+,
  MS Visual C++ 12 (2013) Update 4 an above.
• Removed: MichaelDeque, reason: the implementation is heavy-weighted, inefficient,
  and, seems, unstable.
• Removed: cds::gc::HRC garbage collector, reason: the implementation is inefficient
  and unstable.
• Changed: all container's declaration except StripedSet has been unified to the
  following traits-based form:
  class Container< GC, T, Traits >
• Added: new member function pop_with(Func) to cds::container::TreiberStack
• Added: new member functions enqueue_with(Func), dequeue_with(Func) to
  cds::container::MSQueue
  cds::container::MoirQueue
  cds::container::BasketQueue
  cds::container::OptimisticQueue
  cds::container::RWQueue
  cds::container::SegmentedQueue
  cds::container::TsigasCycleQueue
  cds::container::VyukovMPMCCycleQueue
• Added: new member functions push_with(Func) and pop_with(Func) to cds::container::MSPriorityQueue
• SegmentedQueue: add padding into segmented_queue::traits to eliminate false sharing.
• Changed: guarded_ptr and exempt_ptr have move semantics now. The container's extract() and get()
  member functions return the objects of that type.
• Changed: improved cds::gc::HP and cds::gc::DHP internal implementation
• Changed: map member function insert_key() has been renamed to insert_with()
• Changed: cds/cxx11_atomic.h has been renamed to cds/algo/atomic.h
• Removed: cds/refcounter.h

• Add flat combining (FC) technique and FC-based containers: FCStack, FCQueue, FCDeque, FCPriorityQueue
• Add elimination back-off feature to TreiberStack class
• Add SegmentedQueue - an unfair queue implementation
• New member functions for sets and maps:
  Functions get() and get_with() search a key and return the pointer to item found in safe manner.
  Function extract() searches a key, unlinks the item found from the container and returns pointer to item in safe manner.
  The functions get, get_with, extract, extract_with extract_min, extract_max has been added to the following container:
  SkipListSet, SkipListMap
  EllenBinTree, EllenBinTreeSet, EllenBinTreeMap
  The functions get, get_with, extract, extract_with has been added to the following container:
  MichaelList, LazyList
  MichaelHashSet, MichaelHashMap
  SplitListSet, SplitListMap
• Fix a serious bug in cds::gc::HRC
• Changed MSPriorityQueue to simplify interface and to fix possible pop() deadlock
• Fix a bug in BasketQueue
• Fix EllenBinTree crash under high contention
• Changed: the thread manager detach order to prevent crashing of signal-handled RCU in some case.
• Changed: cds::gc::HP calls Scan() when a thread is detached. This prevents accumulating retired data.
• Changed: minimal boost version is 1.51
• Removed: file cds/lock/rwlock.h

1. Added: EllenBinTree - an implementation of unbalanced binary search
   tree based on paper [2010] F.Ellen, P.Fatourou, E.Ruppert, F.van Breugel
   "Non-blocking Binary Search Tree".
2. Added: MSPriorityQueue - an array-based lock-based priority queue heap,
   see [1996] G.Hunt, M.Michael, S. Parthasarathy, M.Scott "An efficient
   algorithm for concurrent priority queue heaps"
3. Added support for boost.atomic for boost 1.54 and above.
   Now, libcds supports processor architecture like ARM, PowerPC and any other
   that are supported by boost.atomic or by C++11 compiler. Any feedbacks are appreciated.
   To use boost.atomic you should specify -DCDS_USE_BOOST_ATOMIC in compiler's command line.
4. Added: a new CDS_USE_LIBCDS_ATOMIC preprocessor flag has been added to direct
   the compiler to use libcds atomic unconditionally.
5. build.sh has been modified to relax processor architecture and OS requirements.
   This allows to use libcds with native compiler atomic support (or boost.atomic)
   for a processor architecture that has not been tested by libcds's developers.
6. Added support for CLang 3.3
7. Added support for MS VC++ 2013
8. Added support for Mac OS X, see build/sample/build-osx-clang-libc++.sh,
   build/sample/build-osx-gcc.sh for example.
9. Fixed: SkipListSet::erase_with does not take into account "less" predicate parameter.
   10.Fixed: some bugs in SkipListSet leading to deadloop
   11.Fixed: MichaelMap bug: computing hash value for type Q different from key type.

1. Added: user-space RCU garbage collector (5 different implementations), see cds::urcu namespace
2. Added: RCU-related set/map container specializations
3. Added: Skip-list specialization for cds::gc::nogc (undeletable skip-list)
4. For set/map classes: find_with and erase_with member functions have been added. These functions allow to use different predicates for searching.
5. Added: threading model based on С++11 thread_local keyword (CDS_THREADING_CXX11). At present, only gcc 4.8 supports such model.
6. Fixed: bug #11 "ABA bug in libcds 1.3.1 cds/intrusive/msqueue.h" Thanks to Jelle van den Hooff.
7. Added support for GCC 4.8

This is bugfix release:
- Fixed building libcds with boost versions before 1.48. Thanks Lucas Larsch who points me to this problem.

1. Added: StripedSet, StripedMap - hash set and hash map implementation based on fine-grained lock-striping technique

2. Added: CuckooSet, CuckooMap - implementation of cuckoo hashing algorithm based on fine-grained lock-striping technique

3. Added: SkipListSet, SkipListMap - implementation of lock-free skip list

4. Added: template <typename... args=""> emplace(Args&&... args) member function for all containers in cds::container namespace. This function is available only if the compiler supports new C++11 features - variadic templates and move semantics.... read more</typename...>

1. Add: MichaelDeque - deque lock-free algo discovered by Maged Michael

2. Add: BasketQueue - Michael's queue modification discovered by Nir Shavit et al.

3. Add: support of Clang 3.0, 3.1 compiler for amd64, x86 (tested on Linux with boost 1.49)

4. Fixed: solving problem of 8-byte atomic data alignment on 32-bit platforms

5. Fixed bug 3536393: OptimisticQueue core dump

General release
1. Added: C++11 atomic operations support. The library has been rewritten for using std::atomic class and operations proposed in C++11 Standard. If the compiler does not support the standard <atomic> library, own partial implementation declared in cds/cxx11_atomic.h is used. cxx11_atomic.h contains implementation for lock-free part of C++11 <atomic> header needed for libcds.
2. Added: support for C++11 feature (if applicable):
- inline namespace (for GCC 4.4+)
- function =default and =delete specifiers (for GCC 4.4+)
3. Changed: the main reclamation cycle ("liberate" function) of cds::gc::PTB memory reclamation schema has been optimized. Previous implementation could lead to unbounded memory consumption under high contention.
4. Changed: the internal structure of cds::intrusive::OptimisticQueue is greatly simplified. The interface of the class is slightly changed.
5. Fixed: some problem with cds::gc::HRC memory reclamation schema that could be the cause of occasional program crash.
6. Fixed: an error in node reclamation algo in queue implementation (MSQueue, MoirQueue, OptimisticQueue). As an result of the error, some items could be lost with memory leaks.
7. Changed: cds::concept namespace and its content has been removed
8. Added support for Microsoft Visual C++ 11 Beta
9. Added support for GCC 4.7

This version is completely rewritten to support intrusive version of lock-free containers
and more lightweight garbage collectors interface.
The class hierarchy and interfaces have been completely reimplemented from scratch.

1. Added: intrusive containers. Many lock-free containers in libcds have the intrusive
counterparts. The library is fully refactored to support intrusive containers.
Class hierarchy is changed: almost all non-intrusive container classes are based
on their intrusive versions.
Two new namespace is added:
cds::intrusive - for intrusive containers
cds::container - for non-intrusive containers
Namespaces by container type (cds::queue, cds::map and so on) have been removed.
2. Added: New option-based approach is used for class declaration instead
old traits-based one. This approach allows to declare template arguments
in position-independent manner that is very useful for complex template declarations.
Option-based declarations use C++0x variadic templates if compiler supports it (GCC),
otherwise (MS VC) an emulation is used.
3. Changed: garbage collectors interface is generalized. cds::gc::GC (where GC is
one of HP, HRC, PTB) classes has been added.
4. Removed: tagged pointer GC. This GC
- unsafe for complex data structure
- x86-specific since it requires double-width CAS primitive
- memory-consuming since it requires separate free-list for each type stored in the containers
5. Default threading model is changed (see doc for cds::threading namespace):
- for Windows and MSVC++, CDS_THREADING_WIN_TLS is the default now
- for *nix and GCC, CDS_THREADING_PTHREAD is the default now
6. Added GCC 4.6 support (constexpr)
7. Added Microsoft Visual Studio 2010 (vc10) solution

This is general release. New features:
1. Added: cds::Initialize and cds::Terminate functions that initializes and frees library's internal structures.
2. Added: cds::memory::michael::Heap - Michael's lock-free allocator
3. Added: Exponential back-off strategy for spinning
4. Added: cds::queue::vyukov_mpmc_bounded - bounded queue
developed by Dmitry Vyukov (http://www.1024cores.net)
5. Added: support for FreeBSD amd64, x86

This is bug-fix release.

1. [Bug 3157201] Added implementation of threading manager based on Windows TLS API, see cds::threading::wintls::Manager. Added CDS_THREADING_WIN_TLS macro. See docs for cds::threading namespace for details.

2. Fixed bug in cds::threading::pthread::Manager: ptb_gc has not been initialized properly.

3. New function
template <typename T, typename FUNC>
bool erase( const key_type& key, T& dest, FUNC func ) ;
has been added to all map classes.... read more

This is bug-fix release
Changes:

1. [Bug 3130852] cds::queue::TZCyclicQueue::empty() has been corrected
2. [Bug 3128161] It seems, GCC 4.4 has a bug in __thread on x86 and x86_64. New "threading model"
CDS_THREADING_AUTODETECT has been added. See docs of cds::threading namespace for details
3. Fixed errors in the "Pass-the-Buck" garbage collector (namespace cds::gc::ptb)
4. [Bug 3128148] The code is aligned with the C++ standard (minor violations has been removed)
5. [Bug 3141654] missing break statement for atomic store - fixed
6. Added in-place scan strategy to cds::gc::hzp::GarbageCollector. The strategy does not allocate any memory.
7. Fixed bugs in HRC and tagged GC

1. Preliminary support for "Pass The Buck" memory manager is added. See cds::gc::ptb namespace.
2. Many part of library is rewritten to generalize the usage of various GCs
3. The new class cds::details::aligned_allocator has been added for allocating aligned memory
blocks. It is useful for Tagged Pointer memory reclamation schema (cds::gc::tagged_gc).
4. [Break change] New argument has been added to the member functions "ensure" and "find"
for ordered list and map classes
5. New member function "emplace" has been added to ordered list and map classes. This member function
allows change the value (or a part of it) of list/map item.
6. The internal structure of class cds::map::MichaelHashMap is completely refactored to support
cds::gc::no_gc correctly
7. The classes RecursiveSpinT, RecursiveSpin32, RecursiveSpin64, and RecursiveSpin from cds::lock
namespace have been renamed to ReentrantSpinT, ReentrantSpin32, ReentrantSpin64, and ReentrantSpin
respectively
8. Compiler support: GCC version below 4.3.0 is not supported
9. Fixed memory leak in cds::map::SplitOrderedList
10. Added compiler barrier to spin-lock release primitive for x86 and amd64
11. Makefile script is changed to resolve the problem when an user calls 'make clean' directly.
Thanks to Tamas Lengyel to point me to this bug.
12. The file dictionary.txt is exluded from distributive. This file is used for testing purposes only.

The CDS library is totally rewritten using atomic primitives with explicit memory ordering (based on C++ memory model proposal). The implementation of atomic primitives for supported processor architectures is developed from scratch.

This library is an attempt to implement the well-known lock-free algorithms and memory reclamation schemas: Michael & Scott's queue, Michael's hash map, split-ordered list by Shalev & Shavit, Hazard Pointer memory reclamation by Michael's and its modification created by Sundell & Gidenstam and much more.
Supported platforms are:
GNU GCC 4.3:
x86 Linux (32bit)
amd64 (x86-64) Linux (64bit)
ia64 (itanium) Linux (64bit)
ia64 (itanium) HP-UX 11.23 and HP-UX 11.31 (64bit)
sparc (ultrasparc-III) Sun Solaris (64bit)
Microsoft Visual C++ 2008:
x86 Windows (32bit)
amd64 (x86-64) Windows (64bit)