Phobos
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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!