Friday, April 17, 2015

Thesis: Turning Big Data into Small Data, Hardware Aware Approximate Clustering with Randomized SVD and Coresets, Tarik Adnan Moon

Organizing data into groups using unsupervised learning algorithms such as k-means clustering and GMM are some of the most widely used techniques in data exploration and data mining. As these clustering algorithms are iterative by nature, for big datasets it is increasingly challenging to find clusters quickly. The iterative nature of k-means makes it inherently difficult to optimize such algorithms for modern hardware, especially as pushing data through the memory hierarchy is the main bottleneck in modern systems. Therefore, performing on-the- fly unsupervised learning is particularly challenging.

In this thesis, we address this challenge by presenting an ensemble of algorithms to provide hardware-aware clustering along with a road-map for hardware-aware machine learning algorithms. We move beyond simple yet aggressive parallelization useful only for the embarrassingly parallel parts of the algorithms by employing data reduction, re-factoring of the algorithm, as well as, parallelization through SIMD commands of a general purpose processor. We find that careful engineering employing the SIMD instructions available by the processor and hand-tuning reduces response time by about 4 times. Further, by reducing both data dimensionality and data-points by PCA and then coreset-based sampling we get a very good representative sample of the dataset.
This data reduction technique reduces data dimensionality and data-points, effectively reducing the cost of the k-means algorithm by reducing the number of iteration and the total amount of computations. Last but not least, using we can save pre-computed data to compute cluster variations on the fly. Compared to the state of the art using k-means++, our approach offers comparable accuracy while running about 14 times faster, by moving less data fewer times through the memory hierarchy.


Nicolas said...

There are some missing letters and formatting issues in the copied abstract such as:
"it inherently di cult to optimize"
"We nd that careful"
"our approach o ffers comparable"
Missing "ff", "fi" and spaces in the middle of words makes it a little harder to read (but not impossible, a good exercise to see if we can follow ;-) )

Igor said...

It's a feature, not a bug :-)