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Questions tagged [mapreduce]

18 questions
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Are there any non-naive parallel sparse matrix multiplication algorithms?

I was wondering about a problem in analyzing a social network (counting friends-in-common between all pairs of members) that requires squaring its adjacency matrix, and started reading up on algorithms for multiplying sparse matrices. However, all I…
jkff
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Is there a name for "yield first result parallel map"?

Context In randomized algorithms two schemes of computation are common: Las Vegas algorithms with random running time Randomized algorithms that have a probability of success, and have to be executed multiple times before getting the answer You…
Labo
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Decidability of Unary Languages / One-to-One Mapping

I'm trying to prove that there exists an undecidable subset of {1}* by showing a one-to-one correspondence between it and {0, 1}* (which would imply a one-to-one correspondence between their power sets), but I'm struggling with how to do the…
user60640
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Implement K-means clustering with Map-Reduce

Recently in an interview I was asked to implement k-means clustering using the Map Reduce architecture. I know how to implement a simple k-means clustering algorithm but couldn't wrap my head around to do it using Map Reduce(I know what Map Reduce…
user2966197
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Can map-reduce speed up the count-min-sketch algorithm?

Is there any possibility of improvement in the result of count-min-sketch algorithm if we will use Map Reduce approach? Improvement in performance can be in terms of accuracy, time complexity or the work done needed.
Pragya
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2
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numeric stability of map reduce operations

I am building a small library for computing information retrieval metrics for classifiers (precision, recall, f1, accuracy, whatever). Typically each metric is built by calculating a single value for each object being classified (each metric will…
matanox
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Partitioning millions of items into groups based upon a network of set similarities

So I'm working on a problem at work related to the matching of authors of millions of documents. I currently have minhash sets for each document's syntax (sets of 10 numbers with 8-10 digits each), however I need to figure out the most efficient way…
Matt
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Proving $A_{TM}$ is mapping reducible to certain language

I've been asked to prove that the language $A_{TM} = \{ \langle M,w\rangle \mid M$ is a TM that accepts $w\}$ is mapping reducible to the language $LOOP-ONE = \{\langle M \rangle \mid M$ is a Turing machine that doesn't halt on exactly one…
Yarin
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Clarification on MapReduce description in textbook

I am reading through chapter 2 of of the free textbook "Mining of Massive Datasets" (http://www.mmds.org/). On page 28 the following is stated: "It is reasonable to create one Map task for every chunk of the input file(s), but we may wish to create…
ClownInTheMoon
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How does this reduction to prove undecidability account for epsilon?

I have the following proof that the Empty String problem: ES = {M | M accepts $\epsilon$} is undecidable: $f$ = Construct a new machine $M_2$ such that: $M_2$ = given input x erase x from the tape and run M on w: if M accepts w…
Paradox
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Mapping reduction - Bit Flip

Let $L=\{ | M$ is a TM, $L(M)\ne \emptyset$ and $\forall x\in L(M), \overline{x} \notin L(M) \}$ While $\overline{x}$ is the bit flip of $x$. I want to show a mapping reduction to prove that this language is either in R / RE / coRE or none of…
Geo
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N-dimensional generalization of map and reduce?

Is there any conceptual generalization of higher-order functions like map and reduce but for N-dimensional objects (e.g. arrays or tensors)? For mapping, I guess it would be a point-wise generalization. In the case of reduction, I have more doubts…
nohamk
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Why in the Map Reduce Implementation, why not stream the records to the reducer (via TCP) as they are being produced by the mappers?

In the Map-Reduce implementation, the reducers start when all mappers finish their jobs. Why don't we stream the records from mappers to reducers while they are being processed instead? I think there are two reasons: (i) if we use streaming method,…
toantruong
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Karloff's algorithm applied to sparse graphs

I'm given a graph $G = (V, E)$ with $|V| = N$ and $|E| = m \ge N^{1+c}$ edges for some constant $c >0$. $G$ is called a $c$-dense graph. Karloff [1, p.6] has given a map-reduce algorithm called "Finding an MST of a Dense Graph Using…
Pragya
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Prove that DIFFERENTDFA, PDA { | Where M1 is a DFA and M2 is a PDA where L(M1)≠L(M2)} is undecidable

I am absolutely stumped on this one. I am unsure of how to start with this one. I have thought to reducing the problem to Atm. Another thought I have had is to convert M1 to a PDA and use the complement of EQPDA to solve this but I am honestly…
akysu
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