- Documentation
- Reference manual
- The SWI-Prolog library
- library(aggregate): Aggregation operators on backtrackable predicates
- library(ansi_term): Print decorated text to ANSI consoles
- library(apply): Apply predicates on a list
- library(assoc): Association lists
- library(broadcast): Broadcast and receive event notifications
- library(charsio): I/O on Lists of Character Codes
- library(check): Consistency checking
- library(clpb): CLP(B): Constraint Logic Programming over Boolean Variables
- library(clpfd): CLP(FD): Constraint Logic Programming over Finite Domains
- library(clpqr): Constraint Logic Programming over Rationals and Reals
- library(csv): Process CSV (Comma-Separated Values) data
- library(dcg/basics): Various general DCG utilities
- library(dcg/high_order): High order grammar operations
- library(debug): Print debug messages and test assertions
- library(dicts): Dict utilities
- library(error): Error generating support
- library(fastrw): Fast reading and writing of terms
- library(gensym): Generate unique symbols
- library(heaps): heaps/priority queues
- library(increval): Incremental dynamic predicate modification
- library(intercept): Intercept and signal interface
- library(iostream): Utilities to deal with streams
- library(listing): List programs and pretty print clauses
- library(lists): List Manipulation
- library(macros): Macro expansion
- library(main): Provide entry point for scripts
- library(nb_set): Non-backtrackable set
- library(www_browser): Open a URL in the users browser
- library(occurs): Finding and counting sub-terms
- library(option): Option list processing
- library(optparse): command line parsing
- library(ordsets): Ordered set manipulation
- library(pairs): Operations on key-value lists
- library(persistency): Provide persistent dynamic predicates
- library(pio): Pure I/O
- library(portray_text): Portray text
- library(predicate_options): Declare option-processing of predicates
- library(prolog_coverage): Coverage analysis tool
- library(prolog_debug): User level debugging tools
- library(prolog_jiti): Just In Time Indexing (JITI) utilities
- library(prolog_trace): Print access to predicates
- library(prolog_versions): Demand specific (Prolog) versions
- library(prolog_xref): Prolog cross-referencer data collection
- library(quasi_quotations): Define Quasi Quotation syntax
- library(random): Random numbers
- library(rbtrees): Red black trees
- library(readutil): Read utilities
- library(record): Access named fields in a term
- library(registry): Manipulating the Windows registry
- library(rwlocks): Read/write locks
- library(settings): Setting management
- library(statistics): Get information about resource usage
- library(strings): String utilities
- library(simplex): Solve linear programming problems
- library(solution_sequences): Modify solution sequences
- library(tables): XSB interface to tables
- library(terms): Term manipulation
- library(thread): High level thread primitives
- library(thread_pool): Resource bounded thread management
- library(ugraphs): Graph manipulation library
- library(url): Analysing and constructing URL
- library(varnumbers): Utilities for numbered terms
- library(yall): Lambda expressions
- The SWI-Prolog library
- Packages
- Reference manual
A.50 library(rwlocks): Read/write locks
This library implements read/write locks on top of with_mutex/2. Read/write locks are synchronization objects that allow for multiple readers or a single writer to be active.
- with_rwlock(+LockId, :Goal, +ModeSpec)
- with_rwlock(+LockId, :Goal, +ModeSpec, +Options)
- Run Goal, synchronized with LockId in ModeSpec. ModeSpec
is one of
read
,write
,read(Priority)
orwrite(Priority)
. The defaultread
priority is 100 and the defaultwrite
priority is 200. These values prioritize writers over readers. Goal may start if- If there is no goal waiting with higher priority and
- It is a read goal and no write goal is running or
- It is a write goal and no other goal is running.
If Goal may not start immediately the thread waits using thread_wait/2. The Options
timeout
anddeadline
are passed to thread_wait/2. If the time limit is exceeded an exception is raised.Read/write locks are widely critized for their poor behaviour on several workloads. They perform well in scenarios where read operations take long, and write operations are relatively fast and occur only occasionally. Transactions, as implemented by transaction/1,2 are often a better alternative.
This predicate uses a normal mutex and a flag with the same name. See with_mutex/2 and flag/3. Neither the mutex nor the flag should be used directly.
- throws
time_limit_exceeded(rwlock)
if a timeout or deadline is specified and this is exceeded.- bug
- The current implementation is written in Prolog and comes with significant overhead. It is intended to synchronize slow operations.
- If there is no goal waiting with higher priority and