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POIn a multithreaded app, would a multi-core or multiprocessor arrangement be better?
 

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  1. POIn a multithreaded app, would a multi-core or multiprocessor arrangement be better?
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    <p>I've read a lot on this topic already both here (e.g., stackoverflow.com/questions/1713554/threads-processes-vs-multithreading-multi-core-multiprocessor-how-they-are or <a href="https://stackoverflow.com/questions/680684/multi-cpu-multi-core-and-hyper-thread">multi-CPU, multi-core and hyper-thread</a>) and elsewhere (e.g., ixbtlabs.com/articles2/cpu/rmmt-l2-cache.html or software.intel.com/en-us/articles/multi-core-introduction/), but I still am not sure about a couple things that seem very straightforward. So I thought I'd just ask.</p> <p>(1) Is a multi-core processor in which each core has dedicated cache effectively the same as a multiprocessor system (balanced of course for processor speed, cache size, and so on)?</p> <p>(2) Let's say I have some images to analyze (i.e., computer vision), and I have these images loaded into RAM. My app spawns a thread for each image that needs to be analyzed. Will this app on a shared cache multi-core processor run slower than on a dedicated cache multi-core processor, and would the latter run at the same speed as on an equivalent single-core multiprocessor machine?</p> <p>Thank you for the help!</p>
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    1. USCommunity
    1. USMichael Repucci
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      1. POIn a multithreaded app, would a multi-core or multiprocessor arrangement be better?
      1. USmousey
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    1. CORealize that you're dealing in the realm of the theoretical here. From a practical perspective, it's highly unlikely that you're going to notice an appreciable difference among any of those options. If this is just intellectual curiousity, then that's fine, but if you're actually trying to plan around such variables, this is the very definition of premature optimization.
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      1. POIn a multithreaded app, would a multi-core or multiprocessor arrangement be better?
      1. USAdam Robinson
    2. CO@Adam I would disagree. cache effects can have rather spectacular artifacts, moreover, one has to count how communication across bus between cpu packages affects performance and how memory banks are mapped to processors
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      1. POIn a multithreaded app, would a multi-core or multiprocessor arrangement be better?
      1. USAnycorn
    3. CO@aaa: Spectacularity (is that a word?) is in the eye of the beholder. Yes, there are extreme corner cases in which the various setups presented in this question could have striking differences in performance, but a) these situations are exceedingly rare when considering the whole of software development, and b) creating a comprehensive (or even generally well-covered) guide for determining such situations is almost impossible.
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      1. POIn a multithreaded app, would a multi-core or multiprocessor arrangement be better?
      1. USAdam Robinson
 

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