### What is map reduction?

What is map reduction?

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isaaq
4 months ago
Large scale maps are required for urban planning. These provide large space in which detailed information and even the smallest points can be shown. Therefore, at times map is quite big but we have to reduce it according to size of paper and need so that major features may be concentrated upon.
Second step is to reduce or enlarge the grid of squares at new place according to the formula below.
On calculating the size of new square, prepare a new grid which is of same shape and size as the grid on base map is. Give same numeral identification to the squares in new grid. Now cartography the map in each square on the basis of basement square. For better results we may prepare sub-sections of the squares with slanting lines.

Bookish maps or Atlases are necessarily reduced form of basic maps as information on these is to be shown in very small type size. Nowadays it is easier to reduce such maps photographically. Although it is still technically tough job to prepare maps on different scales and then enjoining them to be shown on one scale.

There are several ways of enlargement and reduction of maps but we discuss a method which is very easy and beneficial for students. This method is known as ‘Grid of Squares’ method. In this method, first of all, a map which is to be reduced on enlarge is to be covered with the grid of squares of convenient size, say each of 0.5 cm.

The squares must be marked with very light pencil and should cover whole of the map in a big rectangular or square shape. Each square be given a numeral identity.
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Gaby
3 months ago
MapReduce is a processing technique and a program model for distributed computing based on java. The MapReduce algorithm contains two important tasks, namely Map and Reduce. Map takes a set of data and converts it into another set of data,
where individual elements are broken down into tuples (key/value pairs).
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