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Questions tagged [parallel-computing]

Questions about algorithms or programs that compute on multiple processing units simultaneously. Not to be confused with concurrent or distributed computing!

Common category tags are but also if the question is about parallel complexity (buzzwords include e.g. PRAM or NC).

Find a general introduction on fitting topics on Wikipedia.

In particular, contrast with and which have different focus. See these discussions for more information on this:

That said, if you run into issues in your parallel algorithm, certainly use this tag in addition!

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What is the novelty in MapReduce?

A few years ago, MapReduce was hailed as revolution of distributed programming. There have also been critics but by and large there was an enthusiastic hype. It even got patented! [1] The name is reminiscent of map and reduce in functional…
Raphael
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Distributed vs parallel computing

I often hear people talking about parallel computing and distributed computing, but I'm under the impression that there is no clear boundary between the 2, and people tend to confuse that pretty easily, while I believe it is very…
Charles Menguy
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Difference between Parallel and Concurrent programming?

When looking at concurrent programming, two terms are commonly used i.e. concurrent and parallel. And some programming languages specifically claim support for parallel programming, such as Java. Does this means parallel and concurrent programming…
nish1013
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Which algorithms can not be parallelized?

Is there any algorithm which is very difficult to parallelize or the research is still active? I wanted to know about any algorithm or any research field in parallel computing. Anything, I searched for, has a 'parallel' implementation done. Just…
Polynomial Proton
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P-Completeness and Parallel Computation

I was recently reading about algorithms for checking bisimilarity and read that the problem is P-complete. Furthermore, a consequence of this is that this problem, or any P-complete problem, is unlikely to have an efficient parallel…
Dave Clarke
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Are today's massive parallel processing units able to run cellular automata efficiently?

I wonder whether the massively parallel computation units provided in graphic cards nowadays (one that is programmable in OpenCL, for example) are good enough to simulate 1D cellular automata (or maybe 2D cellular automata?) efficiently. If we…
Stéphane Gimenez
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How to scale down parallel complexity results to constantly many cores?

I have had problems accepting the complexity theoretic view of "efficiently solved by parallel algorithm" which is given by the class NC: NC is the class of problems that can be solved by a parallel algorithm in time $O(\log^cn)$ on $p(n) \in…
Raphael
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Parallelising random reads seems to work well — why?

Consider the following very simple computer program: for i = 1 to n: y[i] = x[p[i]] Here $x$ and $y$ are $n$-element arrays of bytes, and $p$ is an $n$-element array of words. Here $n$ is large, e.g., $n = 2^{31}$ (so that only a negligible…
Jukka Suomela
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Why use SIMD if we have GPGPU?

I thought this question is better served in the CS part of Stack Exchange. Now that we have GPGPUs with languages like CUDA and OpenCL, do the multimedia SIMD extensions (SSE/AVX/NEON) still serve a purpose? I read an article recently about how SSE…
jonfrazen
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Getting parallel items in dependency resolution

I have implemented a topological sort based on the Wikipedia article which I'm using for dependency resolution, but it returns a linear list. What kind of algorithm can I use to find the independent paths?
Masse
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Some questions on parallel computing and the class NC

I have a number of related questions about these two topics. First, most complexity texts only gloss over the class $\mathbb{NC}$. Is there a good resource that covers the research more in depth? For example, something that discusses all of my…
Mike Izbicki
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How does variance in task completion time affect makespan?

Let's say that we have a large collection of tasks $\tau_1, \tau_2, ..., \tau_n$ and a collection of identical (in terms of performance) processors $\rho_1, \rho_2, ..., \rho_m$ which operate completely in parallel. For scenarios of interest, we may…
Patrick87
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Multicore SAT Solver

I am trying to solve a 25k clauses 5k variables SAT problem. As it has been running for an hour (precosat) and I'd like to solve bigger ones afterwards, I'm looking for a multi-core SAT-Solver. As there seem to be many SAT-Solvers, I'm quite…
multsatsolv
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What is the difference between quantum computing and parallel computing?

Quantum computing essentially relies on the fact that qubits maintain multiple possible states simultaneously. Parallel computing too processes multiple states simultaneously. So what is the difference or how are they different?
Raghavendra Singh Dasila
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Are there parallel matrix exponentiation algorithms that are more efficient than sequential multiplication?

One is required to find power (positive integer) of matrix of real numbers. There are lots of efficient matrix multiplication algorithms (e.g. some parallel algorithms are Cannon's, DNS) but are there algorithms that are intended exactly for finding…
TomR
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