map reduce functional programming
DESCRIPTION
A brief introduction of Functional programming using Map Reduce algorithm.TRANSCRIPT
Map Reduce
Map
Double the contents of an array
var a = [1, 2, 3];
for (int I = 0; I < a.length; i++){
a[ i ] = 2*a[ i ];
}
Output:
a = [2, 4, 6];
Double the contents of an array
var a = [1, 2, 3];
for (int i = 0; i < a.length; i++){
a[ i ] = 2*a[ i ];}
var a = [1, 2, 3];
for (int i = 0; i < a.length; i++){
a[ i ] = fn(a[ i ]);}
where fn(x){ return 2*x;}
Double the contents of an array
var a = [1, 2, 3];
for (int i = 0; i < a.length; i++){
a[ i ] = fn(a[ i ]);
} where fn(x){ return 2*x;}
function map(fn, a){
for (int i = 0; i < a.length; i++){
a[ i ] = fn(a[ i ]);
}where fn(x){ return 2*x;}
Double the contents of an array
function map(fn, a){
for (int i = 0; i < a.length; i++){
a[ i ] = fn(a[ i ]);
}where fn(x){ return 2*x;}
map(function(x){ return 2*x;},a}
General Form
Reduce
Sum the contents of an array
function sum(a){
var s= 0;
for(int i=0; i<a.length; i++){
s = s + a[ i ];
}
return s;
}
Sum the contents of an arrayfunction sum(a){
var s= 0;
for(int i=0; i<a.length; i++){
s = s + a[ I ]; }
return s;
}
function sum(a){
var s= 0;
for(int i=0; i<a.length; i++){
s = fn(s, a[ I ]); }
return s;
}
where fn(a, b){ return a+b;}
Sum the contents of an arrayfunction sum(a){
var s= 0;
for(int i=0; i<a.length; i++){
s = fn(s, a[ I ]);
}
return s;
}where fn(a, b){ return a+b;}
function reduce(fn, a, init){
var s= init;
for(int i=0; i<a.length; i++){
s = fn(s, a[ I ]);
}
return s;
}
where fn(a, b){ return a+b;}
Sum the contents of an arrayfunction reduce(fn, a, init){
var s= init;
for(int i=0; i<a.length; i++){
s = fn(s, a[ I ]);
}
return s;
} where fn(a, b){ return a+b;}
General form
reduce(function(a,b){ retun a+b;}, a, init);
Benefits
In case of big arrays, code running on multiple machines, one need not to rewrite the code for computing but just replace the implementation of map and reduce as required.
Microsoft Word Document
map(function(x){ return 2*x;},a}
reduce(function(a,b){ return a+b;}, a, init);
What is hadoop?
Hadoop is parallel, distributive, fault tolerant and network topology aware implementation of MapReduce algorithm.
