A Brief Look at LINQ and Microsoft Orinoco

This was taken from the Microsoft whitepaper on Orinoco. Thanks for the Orinoco team for providing this to me.

Let's assume that you have a number of power meters that you need to monitor. The "InputStream" contains a stream of tuples where each tuple contains a power reading from an individual meter. The reading happens to come in as the wattage times 10.

We can capture each reading a project a new stream that has the normalized wattage. We can also create a sliding 3-second window of meter readings that we can do calculations against.

var realValueStream =

from e in InputStream

select new MeterWattage((double)e.Consumption / 10);

var windowedStream =

from e in realValueStream.SlidingWindow(TimeSpan.FromSeconds(3))

select new MeterWattage(e.wattage);

We can then create a stream that has the average power reading over a sliding 3 second period.

var averagedStream =

from e in windowedStream

select new OneMeterAverage(CEPAggregates.Average(e.wattage));

(I think that this next query may be incorrect, as the ID field was not captured in the windowedStream, but I will continue with the example anyway).

If you want to get the 3-second sliding average for each individual meter, you can do the following 2 queries:

var meterStreamGroups =

from e in windowedStream

group e by e.id;

var groupedAveragedStream =

from eb in meterStreamGroups

from e in eb

select new MeterAverage(eb.Key, CEPAggregates.Avg(e.wattage));

Now, we want to compute the ratio of consumption for each meter over the 3-second window.

var sumStream =

from e in groupedAveragedStream

select new MeterSum(CEPAggregates.Sum(e.wattage));

var ratioStream =

from e1 in groupedAveragedStream

join e2 in sumStream on true equals true

select new

MeterRatio(e1.Id, e1.Wattage, e1.Wattage / e2.TotalWattage);

Finally, we just want to capture the ratio of power consumption from meter #2.

var filteredStream =

from e in ratioStream

where e.id == 2

select e;

©2009 Marc Adler - All Rights Reserved.
All opinions here are personal, and have no relation to my employer.