NEWS

--- 1.21 ---
Improvements:
- Support and testing for clang 19 and gcc 14
- Partial support for thread sanitizer
- Dramatically simplified build system
- Removed numerous unused build configs
- Fixed a minor performance regression from the last release
- Removed hand-imlemented atomics in favor of C11 atomics and existing intrinsics
- Removed unmaintained support for eurekas
- Removed unmaintained support for distributed Qthreads
- Removed various unmaintained debugging and profiling code paths
- Dropped support for numerous compilers that no are no longer available
- Dropped support for various unmaintained architectures like Tilera, Itanium, Alpha, MIPS, and Sparc
- Dropped support for various OS configs that we don't test like Solaris, HPUX, and AIX
- Removed several unmaintained/untested threadqueue and topology detection options

--- 1.20 ---
Improvements:
 - Improve and expand CI testing
 - Fix compilation and testing for an expanded range of platforms, compilers, and operating systems
 - Fix numerous sanitizer errors
 - Remove some unused/outdated code

--- 1.19 ---

New Features:
 - Add a mechanism to reset the default task spawn order
 - Enable the use of HWLOC_GET_TOPOLOGY_FUNCTION

Improvements:
 - Fix fast context swap on ARM64
 - Mature support of ARM64 for Apple MacOS and Linux
 - Improvements to testing
 - Improvements to configure scripts
 - Remove unused files
 - Make version numbering consistent

Notes:
 - Software repository migrated to new locaton

--- 1.18 ---

New Features:
 - Add support for Apple Mac Mx hardware
 - Add spinlock-based implementation of locking API
 - Add support for recursive locks

Improvements:
 - Fix synchronization primitives by adding correct fencing
 - Use stdatomic fence acquire and release for >=C11 
 - Increase default stack size from 4kB to 16kB
 - Fix hang in qt_blocking_subsystem_internal_stopwork on qthreads_finalize 
 - Enable QTHREAD_ARMV8_A64 context swap on Apple Mx hardware
 - Add distributable package gen script

--- 1.17 ---

Improvements:
 - Add GitHub actions for CI testing
 - Add missing include files in the binders topology layer
 - Handle SIGSEGV during configure testing to avoid user exposure
 - Add --with-hwloc-symbol-prefix configure option
 - Add errno preservation from system calls
 - Fix compilation errors on M1 MAC computers
 - Remove Loxley experimental schedulers

--- 1.16 ---

Improvements:
 - Add support for Spack testing (spack test run qthreads)
 - Add support for hwloc2.x (minimal required version is hwloc1.5)

Documentation:
 - User guide for basic Qthreads usage (see userguide subdirectory for LaTex and included code source files)
 
--- 1.15 ---

New Features:
 - Add experimental support for Thread Local Storage and new Condition variable initializers
 - Non-blocking FEB functions are now exposed (e.g. qthread_readFF_nb), other runtimes (e.g. MPI) require access.
 
Improvements:
 - Remove the deprecated register keyword
 - Fix automake machinery so that "make dist" works as expected
 
--- 1.14 ---

New Features:
 - Incorporate minor features requested by Chapel team
 - Add experimental support for the MPI finepoints interface in test/benchmarks/finepoints
 - Added a new thread feature flag for "network tasks", allowing schedulers to treat communication tasks differently
 - Added a RUNTIME_DATA_SIZE flag to qthread_readstate (Courtesy of the Chapel team)
 
Improvements:
 - Read the "no" topology (fix proposed by the Chapel team)
 - Updated SINC implementations to use modern Qthreads APIs
 - Removed deprecated ROSE support
 - Removed deprecated RCRtool support
 
--- 1.13 ---

New Features:
 - Performance Monitoring: use --enable-performance-monitoring
 
--- 1.12 ---

New Features:
 - Pluggable allocators: use --with-alloc={base,chapel} to choose
 
Improvements:
 - Do condwait/backoff in nemesis when getting threads to improve task spawning performance.
 
Bugfixes:
 - Change sleep() and nanosleep() implementation to qt_sleep() and qt_nanosleep() to avoid confusing PMI.
 
--- 1.11 ---

New Features:
 - Distib scheduler: lower contention numa-aware scheduling
 - Binders affinity layer: more control over affinity
 - Updated Portals4 runtime support
 - Added missing XMT FEB operations
 
--- 1.10 ---

New Features:
 - Task queue subsystem
 - Task-level barrier for SPR
 - Environment option to toggle use of guard pages
 
Improvements:
 - Fixed loop constructs to use all workers
 - Unified (and simplified) internal handling of multi-threaded vs single-threaded scheduling regimes
 - Removed defunct SST support, to avoid confusing people
 - Removed futurelib
 - Cleans up affinity subsytem interface and hwloc implementation
 - Added support for Chapel launcher.
 - Added configuration option to enable eureka support; marked as _experimental_
 - Added support for improved compatibility with DUMA tool
 
Bugfixes:
 - Fix various memory leaks associated with spawncache, sincs, preconds, timers.
 - Fix SPR put/get handle bug.
 
--- 1.9 ---

New Features:
 - Eurekas within a team
 - Manual spawn cache flushing (qthread_flushsc())
 - Preliminary Chapel SPR support
 - Unified task-barrier APIs
 
Improvements:
 - Direct context swapping in "direct-yield", used in qt_loop()
 - Better Chapel integration
 - Cleaned up Chapel multinode compilation
 - Detect and work around Apple compiler bugs
 - Qtimer OMP compatibility
 - Can reset a sinc with outstanding submits
 - Compatibility with older libtool versions
 - Reorganized code to make it easier for new developers to understand
 - Better TLS handling
 - Add the ability to query more runtime state (e.g. WORKER_OCCUPATION); fleshes out Chapel support
 - Add HPCCG benchmarks (both pure and via ROSE)
 - Add LULESH benchmark (via ROSE)
 - Better handling of MPI runtime (for multinode)
 - Support for MPICC and MPICXX environment variables (for multinode)
 - Better topology handling
 
Bugfixes:
 - Fix 32-bit fastcontext (broken in 1.8.1)
 - Fix handling of QT_WORKER_UNIT and QT_SHEPHERD_BOUNDARY that are caches (hwloc-only)
 - Properly initialize worker information when QT_NUM_SHEPHERDS has been specified (hwloc-only)
 - OMP barrier nesting improved
 - Correct detection of CMPXCHG16B
 - A bunch of minor bugfixes
 
--- 1.8.1 ---

Improvements:
 - Improved integration with Chapel build system
 - Support for Chapel's blockreport debugging
 - Cheaper context swap on x86(_64)
 
Bugfixes:
 - Support for libnumaV2 fixed
 - Build system avoids obsolete macros
 - Tilera affinity support compiles again (was missing a #include)
 
--- 1.8 ---

New Features:
 - Concurrent lock-free hash table (dictionary); three alternate designs
 - New "simple" tasks: reduced context swap overhead, no stack size limit, but cannot block or yield
 - qthread_spawn() function exposed to simplify complex task creation
 - Arbitrary blocking functions now public (BE CAREFUL)
 - Optional (experimental) lock-free hash table implementation of FEBs (very fast)
 - ARM support
 - Tasks can use a sinc as a return value location
 - spr_init() can replace MPI_Init()
 - spr_unify() converts SPMD to single-flow-of-control
 - C++ version of qt_loopaccum_balance and SPR interface
 - QT_HWPAR environment variable simplifies concurrency management
 
Improvements:
 - LOTS of performance improvements
 - Massive improvement to memory pooling
 - Handle buggy versions of hwloc without crashing
 - Terse multinode documentation
 - Public memory pool now front-end for internal memory pool
 - Scribbling in memory pool (debugging assist)
 - Reduced memory footprint
 - Additional (micro-)benchmarks, including Cilk, TBB, and OpenMP implementations
 - Better checking of compile requirements
 - Faster precondition handling
 - Better Tilera support
 - Configure-time define default stack size
 - Task teams are now reliable
 - Better PPC support (detect all 3 ABIs)
 - Use compiler ("native") TLS when practical
 - Better behavior when topology information is unavailable
 - Use PMI runtime API for multinode
 - Hazardptr implementation works under high load
 - Matt Baker's Chapel syncvar idea
 - Add configure-time "oversubscription" mode; avoids spinlocks, uses sched_yield() when necessary
 - More man pages
 
Bugfixes:
 - Fix distance support with hwloc
 - Fix alignment error in C++ futurelib (old bug)
 - Fix rare hang in Sherwood scheduler
 - Fix pwrite() define (Issue #11)
 - Improve floating-point tests
 - Fix fincr/dincr synchronization bug (some compilers created two reads)
 - Fix BOTS benchmark string handling
 - Fix reinitialization race condition
 - Many minor fixes
 
--- 1.7.1 ---

New Features:
 - New experimental scheduler: loxley
 - Experimental task team support
 - Provide QTHREAD_VERSION in qthread.h
 
Improvements:
 - Significant performance improvements in the scheduler
 - Task-spawn caching
 - More benchmarks in the tests tree
 - Improved memory pool (still not perfect, but now more reliable)
 - Lots of OpenMP support improvements
 - Removed 'volatile' in favor of explicit memory fences (for speed)
 - TilePro/TileGX support
 - Experimental signal-based task termination
 - Updates task ID support with distinct NULL and "not really a qthread" identifiers
 
Bugfixes:
 - Fixed cross-compilation behavior
 - Lots of minor fixes
 
--- 1.7 ---

New Features:
 - Experimental multi-node support with Portals4
 - Task-local data
 - Preconditioned task spawning
 - More control with hwloc: QTHREAD_WORKER_UNIT
 - Several new schedulers: mutexfifo, mtsfifo, nemesis, nottingham
 - Experimental sinc support (counting synchronization, proto-thread-teams)
 
Improvements:
 - Default scheduler: sherwood
 - Updated to new Chapel tasking API
 - Works with Chapel multi-node
 - Better Chapel behavior (e.g. bigger default stack)
 - Faster qsort
 - Even faster thread spawns
 - Better syncvar behavior under contention
 - qthread_num_workers() works independent of scheduler
 - Better debug-output control
 - Tree-based qloop spawning
 - Better behavior in shepherd over-subscription case
 - Use hash to improve qtimer_fastrand() output (still not cryptographically sound)
 - Suppress "Forced X" messages unless QTHREAD_INFO is set
 - Prevents errors if qthread_finalize() is called from the wrong thread
 
Bugfixes:
 - Fix 64-bit increment detection on 32-bit architectures
 - Fix valgrind building
 - Fix PPC building
 - Fix I/O subsystem queueing
 - Many stability improvements
 
--- 1.6 ---

New Features:
 - Brand new C++ qloop interface
 - Supports multi-locale Chapel
 - New scheduling queue options (faster FIFO, and new LIFO)
 - Experimental support for RCRDaemon
 - Experimental support for OpenMP affinity extensions
 - Experimental support for system call intercepting
 
Improvements:
 - Support for external threads using qthread blocking operations
 - Renamed internal context functions, to improve dynamic library loading
 - Chapel interface built as a secondary (static-only) library
 - Reduced exported symbols
 - Updated documentation
 
Bugfixes:
 - Fixed critical fastcontext bug on 32-bit x86
 - Fixed incorrect rounding in atomic operations on old compilers in 32-bit systems
 - Eliminated the faulty test_internal_mod test
 - Fixed qloop memory leak
 - Fixed compiling on 32-bit SparcV9
 
--- 1.5.1 ---

New Features:
 - Chapel shims
 
Improvements:
 - Compiles under Cygwin
 - Better OpenMP nested loop behavior (more efficient barriers)
 - Use memory affinity interface in hwloc (if available)
 - Better CPU affinity behavior for non-default shepherd counts
 
Bugfixes:
 - Better behavior when void functions are used as syncvar-returning threads
 - Pthread_id() now does not change between qthread_initialize() and qthread_finalize()
 - Affinity of calling thread restored during qthread_finalize()
 
--- 1.5 ---

New Features:
 - Multithreaded shepherds (non-default)
 - Qtimer-based fast "random" function
 - Syncvar_t incrF function
 - New qthread_readstate() function, helps support Chapel
 - Convenience functions for storing data in syncvar_t's
 - Removed all library API reliance on qthread_t
 
Improvements:
 - Speed up the qt_feb_barrier with syncvar_t's
 - Speed up context switch on x86/ppc Linux with handwritten one
 - Semi-non-native mode in SST
 - Remove external dependency on C++ and/or cprops
 - Stop using setrlimit unnecessarily on Linux
 - Built-in cache-aware hash for speed and portability
 - Syncvar_t initializers (static and dynamic)
 - Faster thread creation and lower memory footprint
 - MANY improvements to ROSE OpenMP code
 - Faster syncvar_t performance under load
 - Removed deprecated functions
 
Bugfixes:
 - Fixed the race condition in the qt_feb_barrier
 - Fixed C++ headers
 - Match new SST layout
 - Fixed syncvar_t bugs, race-conditions, corner-cases
 - Better behavior with CPU subsets, workaround libnuma bugs
 
--- 1.4 ---

New Features:
 - qarray_dist_like() to match one qarray to another
 - qarray_set_shepof() to specify a qarray segment's location
 - qarray_iter_loopaccum() to accumulate a function over a qarray
 - qt_feb_barrier() to allow threads to engage in a basic barrier
 - qtimer functions, for high-resolution low-overhead cross-platform timing
 - qt_loop_queue* functions, for self-schedule loops
 - syncvar_t datatype can support high-speed asynchronous FEB operations (but
   cannot be treated as a generic integer type); with C++ wrapper
   
Improvements:
 - Renamed DIST_REG_FIELDS and DIST_REG_STRIPES qarray distributions
 - Added FIXED_FIELDS to qarray distributions
 - Increased size of qthread_shepherd_id_t
 - Fixed qthread_dincr() on ppc32
 - Fixed qt_cas() on ppc64
 - Better workaround for broken MacOS X swapcontext()
 - Fixed logic in debug output to avoid floating point
 - Fixed bug in lock profiling code (credit to David Evensky)
 - Better detection of compiler options
 - More ROSE support
 - More valgrind support
 - Work around libnuma brokenness
 - Speed up FEB operations in single-thread case
 - Reworked qt_loop* interface to support loop increments of >1
 - Speed up qloop functions
 - Support hwloc
 - Improved support for parallel build
 
Bugfixes:
 - Fixed the profiling code
 - Fixed the race condition in some qt_loop functions.
 - Properly handle heterogeneous node layouts
 
--- 1.3.1 ---

Improvements:
 - Documentation
 - Fix GCC 4.4 compiler error
 - More ROSE support
 - Better compiler detection
 
--- 1.3 ---

New Features:
 - Optional guard pages, to assist in debugging
 - No longer need to call qthread_finalize()
 - Environment variable QTHREAD_NUM_SHEPHERDS to force a specific number of
   shepherds
 - Shepherds an be enabled/disabled at runtime; threads are forcibly evicted
   from disabled shepherds
 - Support for Tilera systems and Tilera locality libraries
 - A primitive queue-based for-loop to handle imbalanced loop iterations, the qqloop
 
Improvements:
 - Significant speed improvements (and full support) for systems without
   hardware atomic operations
 - Now prefer qthread_initialize(), which doesn't take arguments;
   qthread_init() is deprecated (but still supported)
 - Threads have second-order affinity, only established via explicit programmer
   placement
 - Better detection of insufficient compile environment
 - Better detection of cacheline size
 - Better detection of CPUs on MacOS X and Linux, via sysctl and sysconf
 - Better compatibility with Intel compiler
 - Better Sun Studio ASM support (still fighting ICE)
 - Better interaction with libnuma to detect desired number of shepherds
 - Added a more lightweight qsort() implementation
 - Test codes use environment variables instead of arguments
 - Compatibility with glibc's new qsort_r() function
 - Use autoconf 2.64's C++ "restrict" tests, rather than the broken 2.59 ones
 - Removed small qarray memory leak
 - Standardized C++ detection of integer arguments
 - Fixed error detection in qthread_fork_to()
 - Additional documentation
 - Restored ability to avoid C++ by using cprops library
 - Can now be re-initialized safely
 - No longer relies on PTHREAD_RECURSIVE
 - Use clock_gettime() for timing, if available, instead of gettimeofday()
 
--- 1.2 ---

New Features:
 - Distributed Data Structures: array (qarray), queue (qdqueue), memory pool (qpool)
 - Lock-free Data Structures: queue (qlfqueue)
 - CPU Affinity for shepherds/threads on most systems (not OSX 10.4)
 - Machine topology information can be queried
   - qthread_num_shepherds()
   - qthread_distance()
   - qthread_sorted_sheps()/_remote()
   - qthread_init(0) creates 1 shepherd per location
 - Portable CAS
 - future_fork_to()
 - qthread_cacheline() returns the machine's cache line size in bytes
 
Improvements:
 - Portability improvements
 - Several bugs in queue management fixed
 - Workarounds for bad compiler management of volatile operations
 - Avoid ABA problems in lock-free memory pools
 - Better memory barriers on Sparc
 - Better valgrind support
 - Removed dependency on external cprops library by depending on C++ hash maps
 
--- 1.1.20090123 ---

New Features:
 - Can now force 64-bit alignment
 - Can now migrate threads between shepherds
 - More atomic increments (floating point)
 - Aligned_t qsort()
 - C++ template wrappers to standard FEB functions
 - Environment variable controls stack size
 - SST support
 - High-resolution timers for profiling
 
Improvements:
 - Lock-free internal memory pooling
 - Lock-free thread queueing
 - Better Apple PPC64/PPC/x86/x86_64 support
 - Better Sparc support
 - Better architecture detection
 - Documentation fixes
 - Detects more makecontext() irregularities
 - Better C++ portability/compatibility
 - Better compatibility with unusual compilers
 - Better test cases
 - Uses compiler-builtin atomic operations when available
 - Better 64-bit support
 - Real serial mode
 - Faster qt_loop_balance synchronization
 - Fixed atomic increment volatility declaration
 - Thread counting also checks hash stripe balance
 
--- 1.0 ---

New Features:
 - Added error handling.
 
Improvements:
 - Reorganized osx_compat stuff
 - Released under BSD OSS license with Sandia's blessing!
 - Fixed some portability issues with increment functions.
 
--- 0.8 ---

New Features:
 - Added qloop functions to provide precisely balanced loop spawning. Still
   relatively primitive, but the interface allows for bare-minimum overhead (in
   terms of context-swaps and memory footprint) with more advanced scheduling.
 - Configurable setrlimit and atomic increment use
 
Improvements:
 - Atomic increments are more widely used throughout library.
 - Added qutil documentation
 - Improved futurelib documentation
 - Added workaround for GCC's broken gcse
 - Bugfixes and portability improvements on architectures/environments where
   atomic increments are unsupported
 - Minor improvements to qalloc (from Vitus)
 - Eliminated memory imbalancing by reintroducing locks. (Basic testing shows
   it does not dramatically increase overhead.)
   
--- 0.7 ---

New Features:
 - qthread_incr() can be used for atomic increments
 
--- 0.6 ---

Improvements:
 - Threads now use pthread thread-local (TSD) memory instead of doing lookups
   into bottleneck data-structures
 - Futurelib and qthreads are now more tightly coupled, which obviates some
   bottleneck data-structures
 - Removed locks when spawning qthreads and/or futures from a qthread (locks
   are now only needed in special cases)
 - qthread_lock() and qthread_unlock() are more parallel
 - Better futurelib documentation (see README)
 
--- 0.5 ---

New Features:
 - Threads can have return values, which obey FEB semantics
 - qthread_stackleft() returns the number of bytes left in the stack (with some
   inaccuracy)

Improvements:
 - Functions are now anonymous, and there is no major distinction between
   detached and undetached threads
 - Removed qthread_join(); use qthread_readFF on a thread's return value
   instead
 - FutureLib uses behavior-templates rather than type-templates

Bugfixes:
 - Corrected a race condition in the FEB handling that could lead to deadlock
 
--- 0.4 ---

New Features:
 - man pages for all major functions
 - added qthread_feb_status()

Improvements:
 - changed the qthread_f prototype to be easier to use
 
--- 0.3 ---

New Features:
 - added qthread_writeF(), which as the same arguments and effect as writeEF,
   but does not block
 - added qthread_prepare(), qthread_schedule(), and associated functions to
   decouple thread creation from thread scheduling

Improvements:
 - added information about compiling with the PGI compiler
 - added support for "make check" to test most of the major functionality in
   the library
 - made qthread_fork() (and related functions) significantly faster if called
   from within a qthread by making it possible to avoid using mutexes to
   protect memory pools
 - qthread_shep() may now take a NULL if you don't have a qthread_t handy
   (qthread_shep(NULL) is faster than qthread_shep(qthread_self()))

Bug fixes:
 - corrected the behavior of qthread_readFF() and readFE() (they were
   dereferencing things too many times)
 - qthread_unlock() will now function correctly if unlocking something that's
   already unlocked (it could get into a deadlock situation before, because it
   wasn't cleaning up after itself)
 - fixed a typo in qalloc_dynmalloc() that could cause deadlock on some
   architectures
 - corrected memory pooling to eliminate assertion failures