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Notes on video lecture:
Scalability Basics
Notes taken by Edward Tanguay on July 2, 2014 (go to class or lectures)
Choose from these words to fill the blanks below:
matching, preprocessing, memory, complexity, load, footprint, old, reusing, touch, trees, baked, SQL, computers, core, datasets
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what does scalability mean?
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operationally
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in the past, "scale up"
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needs to work even if data doesn't fit in main              on one machine
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need to bring in data, work on it, then bring in more data, work on it, etc.
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what was important was the size of the memory                   
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this was "out of         " processing of large datasets
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but this began to not be enough since you couldn't bring data on and off fast enough to satisfy the         
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now, "scale out"
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you can increase the speed that you can process the data by making use of 1000s of cheap                   
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algorithmically
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in the past
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algorithm is scalable if when you have n data items, you must do no more than n^m operations, where m is 1 or 2 or some low number, with 4 and beyond it becomes difficult for large                 
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this was tractable, became the definition of scalable
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now:
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n^m/k where k is the number of computers you can apply to the problem
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soon, "streaming data"
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"if you have n data items, you should do no more that n * log(n) operations
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as data grows, you may only get one pass at it
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whenever you hear "log" you should think "          " so this enables you to look at each item and put it in some tree data structure
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example: Large Synoptic Survey Telescope (30TB / night)
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example 1: "Needle in Haystack"
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find                  DNA sequences that equal "GATTACGATATTA"
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linear search
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move through each, compare, until you get a match
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40 records, 40 comparisons
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n records, N comparisons
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algorithmic                      is order N
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sort the sequences
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sort them first, then start in the middle, and move to the direction of the one you are looking for
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after the first check, you remove the need to check half the data
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40 records, 4 comparisons
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but we had to sort the data ahead of time
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algorithmic complexity is log(N) comparisons
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this type of approach to search is            into databases, i.e. "needle in haystack" problems
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e.g. CREATE INDEX seq_idx ON sequence
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this is       -style scalability, i.e. it fits in memory
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builds a platform for building and                indexes
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"there is a lot of work that you are getting for free just by turning your problem into an        statement"
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example 2: "Read Trimming"
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given set of DNA sequences, trim a suffix of each and create a new dataset
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this is a standard                            operation
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linearly
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loop through and process each
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there is no index that is going to help us here, you have to at least            every record
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how can we do better?
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the processing of each doesn't have to do with the processing of the other
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therefore, break dataset into a number of groups and give groups to different processors which process simultaneously
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complexity is N/k, where
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N is the number of items to operate
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k is the number of workers

Vocabulary:

tractable, adj. of a decision problem, algorithmically solvable fast enough to be practically relevant, typically in polynomial time ⇒ "This algorithm proved to be tractable and became the definition of scalable."
Scalability Basics