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Topic: Atomic operation

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	Linux Kernel Documentation :: atomic_ops.txt
		It must be 72 done such that all memory operations before and after the atomic 73 operation calls are strongly ordered with respect to the atomic 74 operation itself.
		Essentially, an array of spinlocks are 278 indexed into based upon the address of the atomic_t being operated 279 on, and that lock protects the atomic operation.
		288 289 Native atomic bit operations are defined to operate on objects aligned 290 to the size of an "unsigned long" C data type, and are least of that 291 size.
	www.mjmwired.net /kernel/Documentation/atomic_ops.txt (2151 words)

	FreeBSD: atomic
		Each of the atomic operations is guaranteed to be atomic in the presence of interrupts.
		As a result, the operation is said to have acquire semantics as it acquires a pseudo-lock requiring further operations to wait until it has completed.
		As a result, the operation is said to have release semantics as it releases any pending data accesses to be completed before its operation is performed.
	nixdoc.net /man-pages/FreeBSD/man9/atomic.9.html (964 words)

	Atomicity - Wikipedia, the free encyclopedia
		For example, isolation relies on atomicity to roll back changes in the event of isolation failures such as deadlock; consistency also relies on rollback in the event of a consistency violation by an illegal transaction.
		Finally, atomicity itself relies on durability to ensure transactions are atomic even in the face of external failures.
		At the hardware level, atomic operations such as test-and-set (TAS), and/or atomic increment/decrement operations are needed.
	en.wikipedia.org /wiki/Atomicity (537 words)

	Chapter 15 Crash Resilience and Persistent Data (Site not responding. Last check: 2007-10-20)
		An atomic operation is implemented so that either all or none of it is done.
		We make an atomic operation repeatable by ensuring that, in the event of a crash, for example, when we do not know whether an operation wrote to persistent store or not, we can restore the system state to its value before the operation started.
		An operation can be made atomic by recording the system state before the operation so that if it does not complete the system can be returned to its original state.
	www.cl.cam.ac.uk /Teaching/current/OSFounds/OSIG/qa15.html (661 words)

	Atomic Force Microscopes - Properties, Principles of Operation and Future Developments (Site not responding. Last check: 2007-10-20)
		In the case of the AFM, the probe is a tip on the end of a cantilever which bends in response to the force between the tip and the sample.
		The Atomic Force Microscope works by scanning a fine ceramic or semiconductor tip over a surface much the same way as a phonograph needle scans a record (for those of you that remember what a record player is!).
		Atomic Force Microspcopy is still used by scientists and engineers today in terms of manipulating atoms and molecules on surfaces.
	www.azonano.com /details.asp?ArticleID=854 (681 words)

	Java theory and practice: Going atomic (Site not responding. Last check: 2007-10-20)
		While writes to volatile variables are guaranteed to be immediately visible to other threads, there is no way to render a read-modify-write sequence of operations atomic, meaning, for example, that a volatile variable cannot be used to reliably implement a mutex (mutual exclusion lock) or a counter.
		operations are atomic read-modify-write operations -- to safely increment the counter, you must take the current value, add one to it, and write the new value out, all as a single operation that cannot be interrupted by another thread.
		The atomic variable classes all expose a compare-and-set primitive (similar to compare-and-swap), which is implemented using the fastest native construct available on the platform (compare-and-swap, load linked/store conditional, or, in the worst case, spin locks).
	www-128.ibm.com /developerworks/java/library/j-jtp11234 (2801 words)

	Nebraskans Witness an Atomic Blast, Operation Cue
		Operation Cue was not the first attempt to test the effects an atomic explosion would have on buildings and houses (constructed of different materials) and cars.
		Nor was it the first to have observers fairly close to the explosion, but it was the first and largest atomic test site that was conducted specifically for civilians.
		Later they hired former FCDA administrator Val Peterson as their "Shelter Products Advisor." One of the ways they advertised was to rebuild the actual Operation Cue building at state fairs and other venues so people could see the building that survived the atomic bomb.
	www.nebraskastudies.org /0900/stories/0901_0131.html (1128 words)

	Atomic Time Zone - Frequently Asked Questions
		Atomic Time Zone is installed and running in the System tray in an even more frequent mode.
		Atomic Time Zone is configured in the Windows 98 Task Scheduler or the user's System Assistant in Microsoft Plus+ profile, which is part of their regular maintenance routine.
		The Atomic Time Zone host server's job is to keep the time accurate on the host and to process requests and send appropriate responses.
	amo.net /AtomicTimeZone/help/ATZ_FAQ.htm (2181 words)

	Lock and Atomic Operation Related Intrinsics
		Atomically write the least significant byte of its 2nd argument to address specified by its 1st argument.
		Atomically write the least significant word of its 2nd argument to address specified by its 1st argument.
		Atomically compare and exchange the value specified by the first argument (a 64-bit pointer).
	www.intel.com /software/products/compilers/clin/docs/ug_cpp/lin1072.htm (545 words)

	atomic variable - UNIX Socket FAQ
		The horrible truth of the matter is that just because it happens to be atomic on an x86 Linux box (I am assuming) does not mean that it will be an atomic operation always...
		I think that atomic operations can avoid a lot mutex overhead, you can for instance check for an atomic_t variable, if it's not set then do stuff, otherwise just do something else (depends on the program).
		Atomic operations are just that: operations that happen atomically, and that's not achieved with global locks or whatsoever as far as I can tell, but with platform specific assembly code.
	www.developerweb.net /forum/showthread.php?t=3294 (1890 words)

	The Remote Enqueue Operation on Networks of Workstations (Site not responding. Last check: 2007-10-20)
		This operation atomically inserts a data element in a queue that physically resides in a remote processor's memory.
		A portion of this operation in implemented on the sender node's network interface, and another portion of this operation is implemented on the receiver node's network interface.
		An enqueue operation is invoked as: enq(vaddress,data) (where vaddress is the virtual address of the base of the first queue buffer and data are the data to be enqueued).
	www.ii.uib.no /~markatos/avg/html_papers/CANPC98/paper.html (4559 words)

	AMO.NET - Atomic Time Zone Software FAQ
		Atomic Time Zone is installed and run like a regular program whenever the user thinks of it, or as part of a regular maintenance routine.
		Atomic Time Zone features a rich array of setting modes that give you lots of flexibility in how it does its work.
		Atomic Time Zone Regular Edition and the ATZ Server Client can be operated in an unattended mode from the Windows 95/98/ME/NT/2000/XP or MS-DOS command line.
	www.amo.net /AtomicTimeZone/help/ATZ_Faq.html (2203 words)

	Atomic Clock Synchronization using the WWVB time signal from Colorado
		Atomic clocks achieve accurate time because atomic clocks are controlled by radio transmitters which themselves receive their time signals from amazingly accurate timepieces, Cesium Atomic Clocks.
		In operation, the atomic clocks are based upon the characteristics of the Cesium 133 atom, whose single electron is known to vibrate at a standard 9,162,613,770 times a second.
		NPL realized the atomic frequency standard for time with the construction of the first long beam apparatus based on the transition of the caesium-133 atom.
	www.ntp-time-server.com /atomic-clocks/atomic-clocks.htm (1088 words)

	[No title]
		OVERVIEW: Atomic_ops.h defines a large collection of operations, each one of which is a combination of an (optional) atomic memory operation, and a memory barrier.
		Also defines associated feature-test macros to determine whether a particular operation is available on the current target hardware (either directly or by synthesis).
		OPERATIONS: Most operations operate on values of type AO_t, which are unsigned integers whose size matches that of pointers on the given architecture.
	www.hpl.hp.com /research/linux/atomic_ops/README.txt (1162 words)

	Atomic operation - Wikipedia, the free encyclopedia
		An atomic operation in computer science refers to a set of operations that can be combined so that they appear to the rest of the system to be a single operation.
		If any of the operations fail then the entire set of operations fails, and the state of the system is restored to the state it was in before any of the operations began.
		As long as there is the possibility of a change in the flow of control, without atomicity there is the possibility that the system can enter an invalid state (invalid as defined by the program, a so-called invariant).
	en.wikipedia.org /wiki/Atomic_(computer_science) (568 words)

	java.util.concurrent.atomic (Java 2 Platform SE 5.0)
		atomically reads and conditionally writes a variable, is ordered with respect to other memory operations on that variable, but otherwise acts as an ordinary non-volatile memory operation.
		Atomic classes are designed primarily as building blocks for implementing non-blocking data structures and related infrastructure classes.
		(Because atomic variables are expected to be mutated, they are poor choices for hash table keys.) Additionally, classes are provided only for those types that are commonly useful in intended applications.
	java.sun.com /j2se/1.5.0/docs/api/java/util/concurrent/atomic/package-summary.html (717 words)

	Wikinfo \| Atomic
		In chemistry, chemical atoms are grouped by type in the periodic table and consist of particles as described by particle physics.
		In computer science, an atomic operation is one that cannot be subdivided.
		Or more specifically, an operation that always completes as a whole, or doesn't complete at all.
	www.wikinfo.org /wiki.php?title=Atomic (143 words)

	Los Alamos National Laboratory: History: Postwar to H-Bomb: Operation SANDSTONE
		The atomic bombs developed and used during World War II were conservative in design and operation.
		Among these events were the overall decision to base national defense on atomic weapons and problems producing significant quantities of fissile material.
		Operation Sandstone, conducted in the spring of 1948, tested weapon designs that met both of these needs.
	www.lanl.gov /history/postwar/sandstone.shtml (447 words)

	Apparatus for locking a portion of a computer memory - Patent 4975870
		A solution to this problem has been to define an "atomic" or "indivisible" operation for performing such data modification, in which no intermediate results of the atomic operation are externally visible--when one process is performing such an operation, no other processes can access the data until the operation is completed.
		The prior-art implementation of this solution has been to "lock" the entire memory for the duration of an atomic operation, meaning that any request by another process to use the memory had to be held pending until the atomic operation was completed.
		An atomic operation by a process will thus have no impact on any other processes save for those occasions when another process wishes to update the very same location(s) as those involved in the atomic operation.
	www.freepatentsonline.com /4975870.html (2505 words)

	An atomic operations library for C++
		For example, an atomic increment operation may be used simply to count the number of times a function is called, as in a profiler.
		In particular, based on earlier discussions, there is a choice to be made as to whether C-level atomic operations should operate only on specially declared "atomic data", or should be usable on arbitrary scalars.
		intrinsics, often operate on scalar data that has not been specially declared, and may thus be used to operate on fields of previously declared structures.
	www.open-std.org /jtc1/sc22/wg21/docs/papers/2006/n2047.html (3220 words)

	Atomic Tutorial
		Atomic actions, as their name lets think, are not interruptible in SugarCubes, so it is the responsibility of the programmer to ensure that they terminate in a finite time (the shortest as possible).
		An atomic expressions in SugarCubes is very close to an atomic action in the sense that it is a piece of java code whose execution is not interruptible.
		The main difference is that an atomic expression returns a value which is used as a parameter for the execution of reactive instruction which use that atomic expression.
	homepage.mac.com /jeanferdinandsusini/v4.0/Atomic.html (1518 words)

	K. Scott Allen : Atomic Operations
		Somewhere along the line, computer science adopted the term “atomic operation” to describe an instruction that is indivisible and uninterruptible by other threads of execution.
		If thread A is writing a 32-bit value to memory as an atomic operation, thread B will never be able to read the memory location and see only the first 16 of 32 bits written out.
		Thread B can only read the value that exists before the atomic operation began, or the value that exists sometime after the atomic operation completes, but can never read the value only partially written.
	odetocode.com /Blogs/scott/archive/2006/05/17/3595.aspx (537 words)

	PART III (Site not responding. Last check: 2007-10-20)
		To extend the study of atomic operations to those which comprise lower level atomic operations.
		An operation which is meaningful at some level may comprise lower level operations that already exist as atomic operations in their own right.
		Because we do not execute (implement) the high level composite operation as a single atomic operation but allow the execution of its components to be interleaved.
	www.cl.cam.ac.uk /Teaching/current/OSFounds/OSIG/hints17.html (374 words)

	OPERATION CRUSADER from Avalon Hill/Atomic Games
		Atomic Games' OPERATION CRUSADER (henceforth referred to as OC) is the first entry in its fledgling _World at War_ (WaW) series; it covers the early stages (pre-Montgomery) of Rommel's Desert War against the Common- wealth forces in North Africa between November 1941 and December 1941.
		For those not familiar with the V4V series, OC is an operational level wargame (the predominant combat units being battalions) which possesses a structure very similar to conventional board wargames.
		Operation Crusader, while not perfect, is clearly at the cutting edge of computer wargaming.
	www.ibiblio.org /GameBytes/issue21/greviews/crusader.html (1602 words)

	Gamasutra - Feature - "Programming Multi-threaded Architectures: Interlocked Operations"
		Interlocked operations are implemented as intrinsic functions and are even translated in some cases to a single processor instruction.
		If the operations were not atomic, there would be a possibility that a thread will read part of an old value and part of a new value from a variable that another thread is writing to.
		Interlocked operations are directly supported by the hardware in the form of one or many processor instructions.
	www.gamasutra.com /features/20060630/paquet_01.shtml (1336 words)

	CISC = atomic operation, RISC = you're nuked (Site not responding. Last check: 2007-10-20)
		We were running on a Motorola 68020 processor that had atomic memory operations.
		The programmer said that one was not needed since the intrinsic generated an atomic instruction for the 68020.
		I'd done some reading about the architecture and there were no atomic memory operations (except one mutex one, I think).
	www.surreal-time.com /WarStories/CISCRISC.html (504 words)

	User-Level Atomic Operations (Site not responding. Last check: 2007-10-20)
		All these operations need to pass one physical address to the network interface, one or more data arguments, and return back the result of the atomic operation.
		Initiating atomic operations from inside the operating system kernel (in order to achieve protection and atomicity) would result in significant overhead, since the operating system overhead would be much higher than the time it takes to do the atomic operation itself.
		User-level initiation of atomic operations is a similar problem to user-level DMA, albeit somewhat simpler, since only one physical address is needed for each atomic operation.
	www.ii.uib.no /~markatos/avg/html_papers/HPCA97/node17.html (215 words)

	Non-interleaved Writes
		The nbytes of data may not be written as one atomic operation.
		One solution to this problem is to specify the maximum number of bytes which may be written in one atomic operation as a parameter which the application program can obtain.
		Because of the nature of pipes, it is usually not practical to guarantee that write operations of any size are not interleaved by write operations from other processes.
	www.itl.nist.gov /div897/staff/barkley/titleissues/node7.html (498 words)

	Novell Documentation: Libraries for C (LibC) - Atomic Functions
		For example, in a multiprocessor environment you should use atomic functions to change the value of a global variable that is not protected by a synchronization primitive and that is accessible by multiple threads.
		For instance, if you use a C increment operator (a++) to increase the value of such a global variable, you have no guarantee that the operation will complete before another thread accesses the variable—a compiler can generate multiple machine language instructions for a++.
		The atomic functions are needed only when multiple threads have access to the same memory location and you have not protected the access with a mutex or some other synchronization device.
	developer.novell.com /documentation/libc/libc_vol2/data/ajbu8xb.html (256 words)

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