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It's a semantic debat, but you seem to redefine parallelism as HPC. I respectfully disagree, parallelism is not necessarily about getting faster, it is really a

by Xixi 12y ago

It's a semantic debat, but you seem to redefine parallelism as HPC. I respectfully disagree, parallelism is not necessarily about getting faster, it is really about actually executing computations simultaneously. Erlang uses parallelism for fault-tolerance purposes, because you need several physical machines running in parallel on different sites to achieve outstanding fault-tolerance. MPI/CUDA/MapReduce uses parallelism for performance reasons. I do not know if it is true as I couldn't find the source, but I remember reading that aircrafts run all computations in parallel on three different architectures (Power and two others), using three different algorithms, to ensure that the results are not compromised either by a faulty algorithm, or a CPU bug. In that case parallelism is used for safety.

seanmcdirmid 12y ago
Sigh...and this is why we are here :) From wiki [1]: > Parallel computing is a form of computation in which many calculations are carried out simultaneously, operating on the principle that large problems can often be divided into smaller ones, which are then solved concurrently ("in parallel"). ... Parallel computer programs are more difficult to write than sequential ones,[5] because concurrency introduces several new classes of potential software bugs, of which race conditions are the most common. And the article for concurrency [2]: > In computer science, concurrency is a property of systems in which several computations are executing simultaneously, and potentially interacting with each other. The computations may be executing on multiple cores in the same chip, preemptively time-shared threads on the same processor, or executed on physically separated processors. [1] http://en.wikipedia.org/wiki/Parallel_computing http://en.wikipedia.org/wiki/Parallel_computing [2] http://en.wikipedia.org/wiki/Concurrency_(computer_science) http://en.wikipedia.org/wiki/Concurrency_(computer_science) Concurrency is a problem (doing things at the same time leads to resource contention), while parallelism is a performance technique. Fault tolerance is something else altogether, and can apply to concurrency problems as well as parallel speedups. Doing things in parallel as a form of redundancy isn't really parallelism...in general, the word parallelism != "in parallel" while concurrency != "concurrently," though they are definitely related. Phew.

by Xixi 12y ago

seanmcdirmid 12y ago

Sigh...and this is why we are here :) From wiki [1]: > Parallel computing is a form of computation in which many calculations are carried out simultaneously, operating on the principle that large problems can often be divided into smaller ones, which are then solved concurrently ("in parallel"). ... Parallel computer programs are more difficult to write than sequential ones,[5] because concurrency introduces several new classes of potential software bugs, of which race conditions are the most common. And the article for concurrency [2]: > In computer science, concurrency is a property of systems in which several computations are executing simultaneously, and potentially interacting with each other. The computations may be executing on multiple cores in the same chip, preemptively time-shared threads on the same processor, or executed on physically separated processors. [1] http://en.wikipedia.org/wiki/Parallel_computing http://en.wikipedia.org/wiki/Parallel_computing [2] http://en.wikipedia.org/wiki/Concurrency_(computer_science) http://en.wikipedia.org/wiki/Concurrency_(computer_science) Concurrency is a problem (doing things at the same time leads to resource contention), while parallelism is a performance technique. Fault tolerance is something else altogether, and can apply to concurrency problems as well as parallel speedups. Doing things in parallel as a form of redundancy isn't really parallelism...in general, the word parallelism != "in parallel" while concurrency != "concurrently," though they are definitely related. Phew.