Phobos Mars on Steriods

Jamie JablinKamran Azam

Suman KarumuriNathan Backman

Map Reduce

• Given the stock data, compute the 200 day moving average for all the stocks.

• Map– Filter stocks not in your portfolio.

• Reduce– Compute the 200 day average for stocks in

your portfolio.

Continuous Map Reduce

• Given the stock data, compute the 200 day moving average for all the stocks every 1 hour.

• Map– Filter stocks not in your portfolio.

• Reduce– Compute the 200 day average for stocks in

your portfolio.

StreamWindow Sub-piece/

Sub-window

At t=0

time

Stream

At t=1WindowSlides

StreamWindow Overlapping

Block

Redundant map computation

Enter Phobos

• Eliminate these redundant map computations.

• On CUDA.• Design

– Instead of computing map on entire window, compute map on the new sub-window.

– Compute the reduce on the whole window.• How? Keep old data around.• How long? In a circular buffer of size num of sub

windows per window.

Implementation

• Updated Mars – Added notion of windowing.– Eliminated redundant computations by using

circular buffer.• Trade off latency for more working

memory.– Keep the old data on host instead of the

device.

Demo time!