Writing a Thesis

On this page you find a listing of thesis topics that are currently available / proposed by members of our group. For each proposal you find a link or an email-address of a contact person.

Aside from this you find more information related to writing a bachelor and master thesis within our group via the following links.

Available, ongoing and completed topics

Paper accepted at SIGMOD 2015: LEMP: Fast Retrieval of Large Entries in a Matrix Product

The paper "LEMP: Fast Retrieval of Large Entries in a Matrix Product" by Christina Teflioudi, Rainer Gemulla, and Olga Mykytiuk was accepted for the SIGMOD 2015 conference in Melbourne, Australia.


We study the problem of efficiently retrieving large entries in the product of two given  matrices, which arises in  a number of data  mining and information retrieval tasks. We focus on the setting where the two input matrices are tall and skinny, i.e.,  with millions of rows  and tens to hundreds  of columns. In such settings,  the product matrix  is large  and its complete  computation is generally infeasible in practice. To address this problem, we propose the LEMP algorithm, which efficiently  retrieves only the large entries  in the product matrix without  actually computing  it.  LEMP  maps the  large-entry retrieval problem  to a  set of  smaller cosine  similarity search  problems, for  which existing methods  can be  used. We  also propose  novel algorithms  for cosine similarity search, which  are tailored to our setting.  Our experimental study on  large  real-world datasets  indicates  that  LEMP is  up  to  an order of  magnitude faster than state-of-the-art approaches.