Matrix Multiplication Optimization

As the final lab assignment for our Concurrent Programming module, we were asked to optimize matrix multiplication. C++ was set as the language and Linux was set as the environment for this task. The tasks for this lab assignment were as follows:

  • Write a naive sequential program to perform matrix multiplication on a n x n matrix containing double precision values. The matrices were to be filled with random double values. Only the time taken for the actual multiplication part was to be recorded.
  • Identify a C++ library for Linux environment which supports parallel for loops and write a parallelized version of the above program.
  • Running the above 2 versions of matrix multiplication for matrix sizes of n = 100 to n = 1000 in increments of 100 and record the time taken for each of these executions.
  • We were then supposed to look in to ways to optimize matrix multiplication taking the processor architecture into account as well and come up with a 3rd version of the matrix multiplication making use of both parallel for loops and various optimization techniques.

The full source code of this project can be found here:

Naive Sequential Version

For this, the standard matrix multiplication algorithm was used. If the matrices are called A, B and C,

for (int i = 0; i < n; i++)
for (int j = 0; j < n; j++)
for (int k = 0; k < n; k++)
C[i][j] += A[i][k] * B[k][j];

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Clustering WSO2 Governance Registry 5.1.0


Recently, I created a Governance Registry cluster on EC2 using Nginx as a load balancer. The cluster created was a 3 node cluster, fronted with Nginx. The initial plan was to create a cluster with 2 Nginx load balancers, one each for the Store components and the Publisher components, as given below.


Originally proposed deployment pattern

As the first step in creating the cluster, I was advised to create a cluster (same deployment pattern as above) of just one G-Reg node. Although I successfully managed to deploy the cluster, there was a major issue in it. The scenario for the G-Reg cluster I was creating was that the artifacts would be deployed by the publishers and as such, the Publisher context should only be accessible by publishers (typically in a company). The artifacts would be consumed by users and they would access these artifacts through the Store. 

Now in the cluster I created, the issue was that  if a user signs in to the Store, he/she would also be able to access the Publisher and vice versa. This is problematic since only the publishers (i.e: the company) should be able to publish artifacts. This is because G-Reg has the Single Sign On (SSO) feature enabled by default. When SSO is used, a user signed into one system can access other, connected systems without the need to sign in again at those particular systems. More on SSO can be found here.

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Creating a WSO2 Application Server cluster using AWS EC2 and Nginx as a load balancer


The WSO2 Application server is used for hosting, deploying and managing applications, built on the WSO2 Carbon platform. A detailed documentation of the Application Server can be found here.

As is the case with other WSO2 products, multiple instances of the Application Server can be installed in a cluster. When in a cluster, the work is shared between the multiple instances although it appears as if though there is only a single instance of the Application Server (AS).

In this tutorial, we will be using AWS EC2 instances to create a AS cluster. The EC2 instances will be Ubuntu based. We’ll be creating a cluster of 3 AS nodes, using Nginx for load balancing and MySQL for storing the user management and registry data of the AS. More information on load balancing can be found here and here.

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