By implementation

Types of algorithms.

Internet addressing.

IP address. An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication. An IP address serves two principal functions: host or network interface identification and location addressing. Its role has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there."

IP addresses are binary numbers, but they are usually stored in text files and displayed in human-readable notations, such as 172.16.254.1 (for IPv4), and 2001:db8:0:1234:0:567:8:1 (for IPv6).

Private/Special addresses. To delay the running out of addresses in IPv4, there are some addresses that are assigned to be private network addresses. These addresses are used for internal networks so that a network of computers can share the same public IP address, hence delaying the running out of IPv4 addresses. These IP addresses cannot be used on the public Internet.

There are two address compression techniques available:

• Leading zeroes can be left out. Therefore, 2001:0db8:00b8:0008:0000:0000:0000:0001 could be written as 2001:db8:b8:8:0:0:0:1

• Any number of sequential, all-zero 'chunks' may be compressed to simply::. This can be done only once in the same address. Thus 2001:0db8:0000:0000:0000:0000:0000:0001 could be written (fully compressed) as 2001:db8::1

Other versions. Versions before IPv4 were never widely used. Version 5 was used exclusively for the Internet Stream Protocol, which was also never widely used. No versions other than 4 or 6 are currently usable on the Internet, and version 4 will eventually be shut off, making version 6 the only usable version.

Classifying Algorithms. There are various ways to classify algorithms, each with its own merits.

· Recursion or iteration

A recursive algorithm is one that invokes (makes reference to) itself repeatedly until a certain condition (also known as termination condition) matches, which is a method common to functional programming.

· Logical

An algorithm may be viewed as controlled logical deduction. This notion may be expressed as: Algorithm = logic + control. The logic component expresses the axioms that may be used in the computation and the control component determines the way in which deduction is applied to the axioms. This is the basis for the logic programming paradigm. In pure logic programming languages the control component is fixed and algorithms are specified by supplying only the logic component. The appeal of this approach is the elegant semantics: a change in the axioms has a well-defined change in the algorithm.

Serial, parallel or distributed

· Deterministic or non-deterministic

Deterministic algorithms solve the problem with exact decision at every step of the algorithm whereas non-deterministic algorithms solve problems via guessing although typical guesses are made more accurate through the use of heuristics.

· Exact or approximate

While many algorithms reach an exact solution, approximation algorithms seek an approximation that is close to the true solution. Approximation may use either a deterministic or a random strategy. Such algorithms have practical value for many hard problems.

· Quantum algorithm

They run on a realistic model of quantum computation. The term is usually used for those algorithms which seem inherently quantum, or use some essential feature of quantum computation such as quantum superposition orquantum entanglement.

Дата добавления: 2014-12-16