What (who) is mark-sweep garbage collection - definition
AUTOMATIC MEMORY MANAGEMENT THAT TRACES WHICH OBJECTS ARE REACHABLE BY A CHAIN OF REFERENCES FROM ROOT OBJECTS AND DEALLOCATES THE REST
Conservative garbage collector; Mark and sweep; Tracing garbage collector; Generational garbage collection; Mark-and-sweep; Stop and copy; Stop-and-copy; Conservative garbage collection; Stop-the-world; Mark–sweep algorithm; Tri-colour marking; Tri-color marking; Generational garbage collector; Mark-sweep algorithm
![object references]]. Circles represent the objects themselves. Objects #1, #2, #3, #4, and #6 are strongly referenced from the root set. On the other hand, objects #5, #7, and #8 are not strongly referenced either directly or indirectly from the root set; therefore, they are garbage.](https://commons.wikimedia.org/wiki/Special:FilePath/Animation of the Naive Mark and Sweep Garbage Collector Algorithm.gif?width=200 "object references]]. Circles represent the objects themselves. Objects #1, #2, #3, #4, and #6 are strongly referenced from the root set. On the other hand, objects #5, #7, and #8 are not strongly referenced either directly or indirectly from the root set; therefore, they are garbage.")
mark-sweep garbage collection
Each cell has a bit reserved for marking which is clear
initially. During garbage collection all active cells are
traced from the root and marked. Then all cells are examined.
Unmarked cells are freed.
garbage collection
![A waste collection barge in [[Venice]], Italy.](https://commons.wikimedia.org/wiki/Special:FilePath/Garbage collecting barge (Venice 2015).jpg?width=200 "A waste collection barge in [[Venice]], Italy.")
![Waste on a sidewalk for collection, bagged and stickered - in [[Dublin]], [[Ireland]]](https://commons.wikimedia.org/wiki/Special:FilePath/Ireland Victor Grigas 2011-15.jpg?width=200 "Waste on a sidewalk for collection, bagged and stickered - in [[Dublin]], [[Ireland]]")
![Bukit Batok West]], Singapore.](https://commons.wikimedia.org/wiki/Special:FilePath/WasteCollection.JPG?width=200 "Bukit Batok West]], Singapore.")
PROCESS OF COLLECTING WASTE
Garbage Collection; Garbage Collector; Civic garbage collection; Waste Collection; Trash pickup; Refuse collection; Garbage collecting; Garbage collection
<programming> (GC) The process by which dynamically allocated
storage is reclaimed during the execution of a program. The
term usually refers to automatic periodic storage reclamation
by the garbage collector (part of the run-time system), as
opposed to explicit code to free specific blocks of memory.
Automatic garbage collection is usually triggered during
memory allocation when the amount free memory falls below some
threshold or after a certain number of allocations. Normal
execution is suspended and the garbage collector is run.
There are many variations on this basic scheme.
Languages like Lisp represent expressions as graphs built
from cells which contain pointers and data. These languages
use automatic dynamic storage allocation to build
expressions. During the evaluation of an expression it is
necessary to reclaim space which is used by subexpressions but
which is no longer pointed to by anything. This reclaimed
memory is returned to the free memory pool for subsequent
reallocation.
Without garbage collection the program's memory requirements
would increase monotonically throughout execution, possibly
exceeding system limits on virtual memory size.
The three main methods are mark-sweep garbage collection,
reference counting and copying garbage collection.
See also the AI koan about garbage collection.
(1997-08-25)
garbage collector
PROCESS OF COLLECTING WASTE
Garbage Collection; Garbage Collector; Civic garbage collection; Waste Collection; Trash pickup; Refuse collection; Garbage collecting; Garbage collection
¦ noun
1. N. Amer. a dustman.
2. Computing a program that automatically removes unwanted data held temporarily in memory during processing.
Wikipedia
Tracing garbage collection
In computer programming, tracing garbage collection is a form of automatic memory management that consists of determining which objects should be deallocated ("garbage collected") by tracing which objects are reachable by a chain of references from certain "root" objects, and considering the rest as "garbage" and collecting them. Tracing garbage collection is the most common type of garbage collection – so much so that "garbage collection" often refers to tracing garbage collection, rather than other methods such as reference counting – and there are a large number of algorithms used in implementation.
