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Ricart-Agrawala algorithm

The Ricart-Agrawala Algorithm is an algorithm for mutual exclusion on a distributed system. This algorithm is an extension and optimization of Lamport’s Distributed Mutual Exclusion Algorithm, by removing the need for <math>release</math> messages.


Algorithm


Terminology

  • A site is any computing device which is running the Ricart-Agrawala Algorithm
  • For any one request of the critical section:
    • The requesting site is the site which is requesting entry into the critical section.
    • The receiving site is every other site which is receiving the request from the requesting site.
  • ts refers to the local timestamp of the system according to its logical clock.


Algorithm

Requesting Site:

  • A requesting site <math>P_i</math> sends a message <math>request(ts, i)</math> to all sites.

Receiving Site:

  • Upon reception of a <math>request(ts, i)</math> message, the receiving site <math>P_j</math> will immediately send a timestamped <math>reply(ts, j)</math> message if and only if:

    • <math>P_j</math> is not requesting or executing the critical section OR
    • <math>P_j</math> is requesting the critical section but sent a request with a higher timestamp than the timestamp of <math>P_i</math>
  • Otherwise, <math>P_j</math> will defer the <math>reply</math> message.

Critical Section:

  • Site <math>P_i</math> enters its critical section only after receiving all <math>reply</math> messages.
  • Upon exiting the critical section, <math>P_i</math> sends all deferred <math>reply</math> messages.


Performance

  • Number of network messages; 2*(N-1)
  • Synchronization Delays: One message propagation delay


Common Optimizations

Once site <math>P_i</math> has received a <math>reply</math> message from site <math>P_j</math>, site <math>P_i</math> may enter the critical section without receiving permission from <math>P_j</math> until <math>P_i</math> has sent a <math>reply</math> message to <math>P_j</math>


Problems

One of the problems in this algorithm is failure of a node. In such a situation a process may starve forever.
This problem can be solved by detecting failure of nodes after some timeout.


See also

  • Lamport’s Bakery Algorithm
  • Lamport’s Distributed Mutual Exclusion Algorithm
  • Maekawa’s Algorithm
  • Suzuki-Kasami’s Algorithm
  • Raymond’s Algorithm

Method signature

In computer programming, especially object-oriented programming, a method is commonly identified by its unique method signature. This usually includes the method name, the number and type of its parameters, and its return type. A method signature is the smallest type of a method.

In the Objective-C programming language, method signatures for an object are declared in the interface header file. For example, 

- (id)initWithInt:(int)value;

defines a method initWithInt that returns a general object (an id) and takes one integer argument. Objective-C only requires a type in a signature to be explicit when the type is not id; this signature is equivalent:

- initWithInt:(int)value;

In the Java programming language, method signatures for an object is the method name and the number and type of its parameters. Return types are not considered to be a part of the method signature. 

- return_type method_name(parameters) {...}


See also

  • Type signature

Shadow

A shadow is a region of darkness where light is blocked. It occupies all of the space behind an opaque object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, or reverse projection of the object blocking the light. It begins as the light moving through but is blocked depending on the density.


Features

The closer to 90 degrees the angle between an elongated object and the direction of the light it blocks, the bigger its shadow. The smaller the angle between the direction of the light and the surface on which the shadow occurs, the longer the shadow is. If the object is close to the light source, the shadow is large. If the surface is curved there are further distortions.


Non-Point

For a non-point source of light, the shadow is divided into the umbra and penumbra. The wider the light source, the more blurred the shadow.

If there are multiple light sources there are multiple shadows, with overlapping parts darker, or a combination of colors. For a person or object touching the surface, like a person standing on the ground, or a pole in the ground, these converge at the point of touch.


Coloured shadows

If white light is produced by separate coloured light sources, the shadows are coloured.

Illuminate a room with a red light, and the shadows are exclusively gray, or dark. Illuminate the shadows with a white light, and the shadows are green. Where both lights are blocked, or in other words where the shadows intersect, the shadows are gray. Away from the intersection, where the red light is blocked the shadows are green, and where the white light is blocked the shadows are red. In other words, light colors shadows or brightens them, according to the complementary color of the light blocked to cast the shadow. In the case of white and red lights, the complement of white is red; with white and green lights, the complement of white is green.

In the absence of multiple light sources, colored lights illuminate spaces where other lights are not blocked. In the above example, the red shadow cast by blocking white light is not a shadow with the white light off, but it is illuminated in red.

In the absence of white light, colored lights blocked by an opaque surface cast shadows in the colors complementary to the lights blocked. For green light, red shadows, and vice-versa; blue, orange; yellow, purple; intermediate light, intermediate shadows.


Shadow propagation speed

The further the distance from the object blocking the light to the surface of projection, the larger the silhouette (they are considered proportional). Also, if the object is moving, the shadow cast by the object will project an image with dimensions (length) expanding proportionally faster than the object’s own length of movement. The increase of size and movement is also true if the distance between the object of interference and the light source are closer. This, however, does not mean the shadow may move faster than light, even when projected at vast distances, such as light years. The loss of light, which projects the shadow, will move towards the surface of projection at light speed.

The projected shadow may appear to have moved faster than the speed of light, but there is no actual physical manifestation moving upon the surface. The misconception is that the edge of a shadow “moves” along a wall, when in actuality the increase of a shadow’s length is part of a new projection, which will propagate at the speed of light from the object of interference. Since there is no actual communication between points in a shadow (except for reflection or interference of light, at the speed of light), a shadow that projects over a surface of large distances (light years) cannot give information between those distances with the shadow’s edge. [1]


Other notes

A shadow cast by the Earth on the Moon is a lunar eclipse. Conversely, a shadow cast by the Moon on the Earth is a solar eclipse.

On satellite imagery and aerial photographs, taken vertically, tall buildings can be recognized as such by their long shadows (if the photographs are not taken in the tropics around noon), while these also show more of the shape of these buildings.

A shadow shows, apart from distortion, the same image as the silhouette when looking at the object from the sun-side, hence the mirror image of the silhouette seen from the other side (see picture).

Shadow as a term is often used for any occlusion, not just those with respect to light. For example, a rain shadow is a dry area, which, with respect to the prevailing wind direction, is beyond a mountain range; the range is “blocking” water from crossing the area. An acoustic shadow can be created by terrain as well that will leave spots that can’t easily hear sounds from a distance.


Mythological connotations

An unattended shadow or shade was thought by some cultures to be similar to that of a ghost, a flicker of a life unable to end for some reason.

It is also believed as an alternative construct that shadows are in fact a representation of God’s presence around an object; like a halo. Early eastern beliefs also play to this theory. For example, Vishnu (a prominent Hindu god) would appear to help followers by assisting with tasks by lending some of its extra arms to assist the burden of the person.

In many works of modern fantasy, shadows are often intertwined with dark arts and black magic.


Heraldry

In heraldry, when a charge is supposedly shown in shadow (the appearance is of the charge merely being outlined in a neutral tint rather than being of one or more tinctures different from the field on which it is placed), it is called umbrated. Supposedly only a limited number of specific charges can be so depicted.


See also

  • Shade
  • Shadow play
  • Shadow people

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Demo (King Diamond demo)

This is a demo album by the heavy metal band King Diamond.


Track listing

  1. “The Candle” – 6:38
  2. “Haunted” – 3:55
  3. “Dressed in White” – 3:09
  4. “The Portrait” – 4:54
  5. “Lurking in the Dark” – 3:38
  6. “Shadow Night” – 7:19 (Mercyful Fate cover)


Credits

  • King Diamond - Vocals
  • Michael Denner - Guitars
  • Timi Hansen - Bass
  • Mikkey Dee - Drums

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Carnac the Magnificent

Carnac the Magnificent was a role played by Johnny Carson on The Tonight Show Starring Johnny Carson, and later continued on Late Show with David Letterman, occasionally by Paul Shaffer. One of Carson’s most well-known characters, Carnac was a psychic with a large, elaborate turban and a plethora of envelopes, all of which (according to Ed McMahon) were “hermetically sealed” and had been kept in “a mayonnaise jar on Funk and Wagnalls’ porch since noon” that day. On the way to his desk after arriving on stage, Carnac would invariably trip and fall (on one memorable occasion, Carson’s desk had been replaced with a balsa-wood version, and he smashed right through it).

Carnac’s act involved a variation of the magician’s billet reading trick: divining the answer to a question putatively written on a card sealed inside one of the envelopes, then opening the envelope to reveal the question. The resulting jokes were usually intentionally corny and often involved puns in some way:

(Carnac holds the sealed envelope up to his turban)
CARNAC: Sis boom bah.
ED McMAHON: Sis boom bah?
(Carnac rips the envelope open and removes the card)
CARNAC (reading): Describe the sound made when a sheep explodes.

or

(Carnac holds the sealed envelope up to his turban)
CARNAC: The La Brea Tar Pits.
ED McMAHON: The La Brea Tar Pits?
(Carnac rips the envelope open and removes the card)
CARNAC (reading): What you have left after eating the La Brea Tar Peaches.

or

(Carnac holds the sealed envelope up to his turban)
CARNAC: U-C-L-A, A-F-L, C-I-O.
ED McMAHON: U-C-L-A, A-F-L, C-I-O?
(Carnac rips the envelope open and removes the card)
CARNAC (reading): How do you spell ucaliflicio?

or

(Carnac holds the sealed envelope up to his turban)
CARNAC: Green Acres.
ED McMAHON: Green Acres?
(Carnac rips the envelope open and removes the card)
CARNAC (reading): What Kermit has after Miss Piggy kicks him in the groin.

or

(Carnac holds the sealed envelope up to his turban)
CARNAC: Dippity Do.
ED McMAHON: Dippity Do?
(Carnac rips the envelope open and removes the card)
CARNAC (reading): What forms on your dippity early in the morning..

or

(Carnac holds the sealed envelope up to his turban)
CARNAC: 105.
ED McMAHON: 105?
(Carnac rips the envelope open and removes the card)
CARNAC (reading): At what age will a person qualify for Social Security under the Reagan Administration’s plan?

Audience reaction played a major role in the skit. If a joke generated a negative response from the audience, Carson/Carnac would cast a comedic curse (e.g., “May a bloated yak change the temperature of your jacuzzi”) upon them. Occasionally the curse would be directed at Ed McMahon if his introduction of Carnac’s abilities became too over-the-top. Such “curses” were also standard when the crowd cheered as McMahon announced the final envelope.

The Late Show With David Letterman sometimes pays homage to the skit, with Paul Shaffer as Carnac.


External links

  • Carnac the Magnificent at johnnycarson.com - includes video clips of Carson as Carnac

Bridge of the Gods (modern structure)

The Bridge of the Gods is a steel truss cantilever bridge that spans the Columbia River between Cascade Locks, Oregon and Washington state near Stevenson. It is approximately 40 mi (64 km) east of Portland, Oregon and 4 miles (6.4 km) upriver from the Bonneville Dam. It currently serves as a toll bridge operated by the Port of Cascade Locks.

The bridge was built by the Wauna Toll Bridge Company of Walla Walla, Washington and opened in 1926 as a 1,127 ft bridge. The higher river levels resulting from the construction of the Bonneville Dam required the bridge to be further elevated and extended to its current length of 1,856 ft.

The bridge is named after a famous geologic event also known as Bridge of the Gods.

The Pacific Crest Trail crosses the Columbia River on the Bridge of the Gods and the lowest elevation of the trail is on this bridge.


External links

  • One site on the modern-day Bridge of the Gods
  • Port of Cascade Locks official site

Write buffer

A write buffer, or buffered write-through, is a type of memory buffer.

A variation of write-through where the cache uses a “write buffer” to hold data being written back to main memory. This frees the cache to service read requests while the write is taking place. There is usually only one stage of buffering so subsequent writes must wait until the first is complete. Most accesses are reads so buffered write-through is only useful for very slow main memory.

ProgPower

ProgPower is the name of four progressive and power metal festivals:

  • ProgPower Europe (formerly called ProgPower), held in the Netherlands since 1999
  • ProgPower USA, held in the United States since 2001
  • ProgPower UK, held in the United Kingdom since 2006
  • ProgPower Scandinavia, held in Denmark since 2007

Charles Fredrick Wiesenthal

Charles Fredrick Wiesenthal was awarded the patent for the first known mechanical device for sewing in 1755. One might argue that he invented the sewing machine. He was born in Germany, but was in England at the time of invention. For his invention of a double pointed needle with an eye at one end, he received the British Patent No. 701 (1755). The design did have some mechanical limitations.

Stade Cavani

Stade Cavani is a multi-use stadium in Mamoudzou, Mayotte. It is currently used mostly for football matches. The stadium holds 5,000.

Finance charge

In United States law, a finance charge is any fee representing the cost of credit, or the cost of borrowing. It includes not only interest but other charges as well, such as transaction fees. Details regarding the federal definition of finance charge are found in the Truth-in-Lending Act and Regulation Z, promulgated by the Federal Reserve Board.


External Links

A Finance Charge Tutorial

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Allen Walker Read

Allen Walker Read (June 1
Who Was Who in North American Name Study, American Name Society, accessed February 15, 2007
or 2,
The Times, November 8, 2002, obituary
Luther, Claudia, South Coast Today, October 21, 2002, obituary
1906 - October 16, 2002) was an American etymologist and lexicographer, best known for his studies into the words “okay” and “fuck.”

Read was born in Winnebago, Minnesota, earned a bachelor’s degree from the University of Northern Iowa (then called Iowa State Teachers College) in 1925, a master’s degree from the University of Iowa in 1926, and studied at the University of Oxford as a Rhodes Scholar from 1928-1931. He was a chaired professor at Columbia University in New York City from 1945 until 1975.

He was a repeated contributor to American Speech by 1931; his first extended work, Lexical Evidence from Folk Epigraphy in Western North America: A Glossarial Study of the Low Element in the English Vocabulary, was privately published in Paris in 1935 since its description of bathroom graffiti was considered too racy for American publishers. It was eventually published in the United States in 1977, under the title Classic American Graffiti, ISBN 0916500063.

He married Charlotte Schuchardt in 1953. They remained together until she died in July 2002. He died in New York City three months later. They had no children.


References


External links

  • An essay on goodbyemag.com.
  • An obituary on Economist.com.

Non-coding strand

DNA is composed of two strands of nucleotides that are bound together through several types of chemical interactions. RNA polymerase reads one of these strands, the template or coding strand, and produces an mRNA transcript, which is later translated into a protein. The DNA strand that is “read” by the polymerase is the Non-coding or template strand(coding DNA strand will have the same nucleotide sequence as the mRNA transcript read from the template strand but with uracil instead of thiamine). The coding strand always grows and is always read in the 5′ to3′ direction. Seemingly useless coding DNA strand is just one of the mechanisms live organisms created to decrease the chances of a random mutation of extremely valuable DNA strand. The addition of a second strand of DNA decreases the chance of nucleotides shifting along the strand, but unfortunately when a non-coding DNA strand is present a “point mutation” can occur. Point mutation is a situation in which a connected pair of nucleotides (A and T or C and G) will flip and nucleotides will take each other’s places on the opposite strand.

Whitchurch Lock

Whitchurch Lock is a lock and weir situated on the River Thames in England. The lock is located in the Oxfordshire village of Whitchurch-on-Thames but the weir crosses the river to the Berkshire village of Pangbourne. Both lock and weir are owned and managed by the Environment Agency.

The long serving lock keeper is Brian Butcher who has worked on the river for more than forty years starting as an apprentice engineer for Bert Bushnell’s hire fleet based in Maidenhead in the 1960s.


Access to the lock

Whitchurch Lock is one of the few locks on the River Thames which has no public access other than by boat.


Reach above the lock

The reach passes along the Chiltern Hills, culminating in Goring Gap. On the Oxfordshire side are Hartslock beech woods, named after a lock that was removed in 1910. On the Berksire side is Child Beale Wildlife Park. The Thames Path crosses Whitchurch Bridge into Oxfordshire and continues through Whitchurch away from the river as it goes round Coombe Park, returning to the river at Hartslock. It continues on the Oxfordshire river bank to Goring.


See also

  • Locks on the River Thames

{{UK-canal-stub}

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Taffel

Taffel is a company located on Åland, an autonomous territory of Finland, producing potato chips and other savoury delights. Four kilograms of potatoes are needed to produce one kilogram of Taffel chips.


External links

  • Company site

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Kernel Transaction Manager

Kernel Transaction Manager (KTM) is a component of the Windows operating system kernel in Windows Vista and Windows Server 2008 that enables applications to use atomic transactions on resources by making them available as kernel objects. The transaction engine, which operates in kernel mode, allows for transactions on both kernel mode and user mode resources, as well as among distributed resources. The Kernel Transaction Manager intends to make it easy for application developers to do a lot of error recovery, virtually transparently, with KTM acting as a transaction manager that transaction clients can plug into. Those transaction clients can be third-party clients that want to initiate transactions on resources that are managed by Transaction Resource Manager. The resource managers can also be third-party or built into the system.

KTM is used to implement Transactional NTFS (TxF) and Transactional Registry (TxR). KTM relies on the Common Log File System (CLFS) for its operation. CLFS is a high-performance, general-purpose log-file subsystem that dedicated user-mode and kernel-mode client applications can use and multiple clients can share to optimize log access and for data and event management and enable transactions.


External links

  • Kernel Transaction Manager on MSDN

Small-c conservative

A small-c conservative is anyone who believes in the philosophy of conservatism but does not necessarily identify with an official Conservative Party.


Canadian context

The term was especially popular in Canada during the 1990s when the Progressive Conservative Party was centre-right with the Reform Party (later, the Canadian Alliance) further to the right. Members and supporters of the Reform Party/Canadian Alliance would thus describe themselves as small-c conservatives.


UK

context

This term is also used in the United Kingdom to describe right wingers who do not support the UK Conservative Party.


See also

  • small-l liberal
  • small-l libertarianism
  • Blue Tory
  • Red Tory

Forex swap

In finance, a forex swap (or FX swap) is an over-the-counter short term interest rate derivative instrument. In emerging money markets, forex swaps are usually the first derivative instrument to be traded, ahead of forward rate agreements.


Structure

A forex swap consists of two legs:

  • a spot foreign exchange transaction, and
  • a forward foreign exchange transaction.

These two legs are executed simultaneously for the same quantity, and therefore offset each other.


Uses

Forex swaps are used for hedging or speculation.


Hedging

Investors use forex swaps to hedge their existing forex exposures by swapping temporary surplus funds in one currency into another currency for better use of liquidity. Doing so protects against adverse movements in the forex rate, but favourable moves are renounced.


Speculation

Investors use forex swaps to speculate on changes in the interest rate differentials between two currencies.

The relationship between spot and forward is as follows:

<math>
F = S \left( \frac{1+r_T T}{1+r_B T}\right)
</math>

where:

  • F = forward
  • S = spot
  • rT = interest rate of the term currency
  • rB = interest rate of the base currency
  • T = tenor (calculated according to the appropriate day count convention)

The forward points or swap points are quoted as the difference between forward and spot, F - S, and is expressed as the following:

<math>
F - S = S \left( \frac{1+r_T T}{1+r_B T} -1 \right) \approx S \left( r_T - r_B \right) T
</math>

where rT and rB are small. Thus, the absolute value of the swap points increases when the interest rate differential gets larger, and vice versa.


Related instruments

A forex swap should not be confused with a currency swap, which is a much rarer, long term transaction, governed by a slightly different set of rules.


See also

  • Currency swap
  • Overnight index swap
  • Foreign exchange market
  • Interest rate swap
  • Identity columns Each transaction locks this table, increments the number, and then commits; Furthermore, it is possible that a given identity column can appear to have
  • Rubyisms - MySQL-dump This cannot happen if you implement each transaction and its inverse in the same Furthermore, I've never noticed Rails to use a transaction for SELECT,
  • COMPETITION IN ELECTRONIC COMMERCE Furthermore, each credit card association would benefit by being able to 1) . Thus, if the transaction schemes for secure credit card commerce on the
  • Linking Anonymous Transactions: The Consistent View Attack File Format: PDF/Adobe Acrobat - View as HTMLFurthermore, we assume that boolean circuits are acyclic and consist only of. gates of type NAND where each gate has two inputs. The above assumptions
  • Computer Fraud & Security : Security in Mobile Environments: If Obviously, within the transaction data packet there is room for identification of the merchant, the service and the buyer. Furthermore, each step in the
  • A Framework for Infection Control Surveillance Using Association Rules be a set of transactions, e.g., culture reports, where each transaction T is a set Furthermore, itemsets with minimum support are called large itemsets,
  • MEMORANDUM FOR CHIEF INFORMATION OFFICERS File Format: PDF/Adobe Acrobat - View as HTMLinformation reported on each transaction. Agencies’ GPEA progress reports will Furthermore, guidance on other. implementation issues covered by GPEA has
  • PostgreSQL Concurrency Issues File Format: PDF/Adobe Acrobat - View as HTMLEach transaction runs against a notional “snapshot” of the committed state . Furthermore,. SELECT FOR UPDATE. returns the latest updated contents of
  • RISK MANAGEMENT SOLUTIONS File Format: PDF/Adobe Acrobat - View as HTMLFurthermore, if you wish to create a. new screening profile, this can be deployed characteristics of each transaction, performing thousands of checks.
  • Sec w/o ID This same number is used by the owner to allow each transaction; Furthermore, tracing information can be used as an identifier to link together all the
  • Global Finance Journal : The no-arbitrage condition and financial Furthermore, the paper shows that, in financial markets with transaction . Furthermore, each of (Pf) and Eq. (4) hold if, and only if, there exists a
  • ACM Queue - Unlocking Concurrency: Multicore programming with Instead, the system "under the hood" allows multiple transactions to execute concurrently as long as it can still provide atomicity and isolation for each
  • [Paper] Mining Balanced Patterns in Web Access Data Further- more, the new pruning threshold is intuitive from an ana- lysts perspective. Each transaction is an itemset, i.e., a subset of {1, 2, 3,
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Join

Join may refer to:

  • join (SQL), a SQL and relational database operation
  • join (law), to include additional counts or additional defendants on an indictment
  • join (Unix), the Unix join command.
  • In lattice theory, a join is a least upper bound
  • Join (topology), an operation combining two topological spaces
  • In relational algebra, the join is composition of relations.
  • join calculus


See also

  • joiner
  • joinery
  • joint (disambiguation)

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Shear line (locksmithing)

In lock picking a cylinder lock, the shear line, also known as the split line in Australia, is where the inner cylinder ends and the outer cylinder begins. When a correct change key or master key is inserted in the cylinder, it will align the pin segments with the shearline and allow the cylinder to be turned. This break in the lock mechanism is a vital part of the lockpicking process, as it allows a picked pin to “hang” while the others are being picked.

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Boundary case

The term boundary case is frequently used in software engineering to refer to the behavior of a system when one of its inputs is at or just beyond its maximum or minimum limits. It is frequently used when discussing software testing.

For example, if an input field is meant to accept only integer values 0 - 100, entering the values -1, 0, 100, and 101 would represent the boundary cases.

It is commonly thought that three cases should be used when boundary testing (one on the boundary, and one on either side to it). However, the case on the valid side of the boundary is redundant, and so equivalence partitioning recommends skipping it.


See also

  • Black box testing
  • Boundary value analysis
  • Corner case
  • Edge case

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City Mill River

City Mill River is part of the Bow Back Rivers in London. The lock, City Mill Lock is currently disused but, in conjunction with new homes built alongside, work is underway to re-open it. Before that however, work must be completed to clear the waterway of silt and plant growth (water pennywort, Hydrocotyle ranunculoides, a member of the apiaceae family).