fold

Class: matlab.compiler.mlspark.RDD
Namespace: matlab.compiler.mlspark

Aggregate elements of each partition and the subsequent results for all partitions

Syntax

result = fold(obj,zeroValue,func)


Description

result = fold(obj,zeroValue,func) aggregates the elements of each partition in obj and the subsequent results for all the partitions, using an associative function func and a neutral “zero value” represented by zeroValue.

Input Arguments

obj — Input RDD

RDD object

An input RDD, specified as a RDD object.

zeroValue — Neutral “zero value”

cell array of numbers

A neutral “zero value”, specified as a cell array of numbers.

Data Types: cell

func — Function for the folding action

function handle

A function for the folding action, specified as a function handle.

Data Types: function_handle

Output Arguments

result — Result of the folding action

scalar

Result of the folding action, returned as a scalar.

Examples

Accumulate the Elements of Each Partition and Subsequent Partitions

%% Connect to Spark
sparkProp = containers.Map({'spark.executor.cores'}, {'1'});
conf = matlab.compiler.mlspark.SparkConf('AppName','myApp', ...
                        'Master','local[1]','SparkProperties',sparkProp);
sc = matlab.compiler.mlspark.SparkContext(conf);

%% fold
foldVal = sc.parallelize({1, 2, 3, 4, 5}, 1).fold(10, @(x,y)(x+y));
disp(foldVal);

Version History

Introduced in R2016b