Hyperthreading

In a hyperthreaded CPU, for each processor core that is physically present, the operating system addresses two virtual or logical cores, and shares the workload between them when possible.

Processors

Relates to issues dealing with multiple processors



Thread threads program

Example

"A quad core intel cpu s with hyperthreading enabled has 4 physical cores yet 8 logical processors hyperthreading creates 4 more logical processors"

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C/C++/Assembly Programatically detect if hyper-threading is active on Windows, Mac and Linux

"Ow many cores does your processors have and does your processors have hyperthreading enabled if your processors only has one thread trying to multithread will actually slow your processors down;if your processors has more you can use as many threads in your program as you have available in the os"

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Brute force on several BackgroundWorkers faster?

Others

Example

Logical processors share nearly all other resources on the physical processors such as caches execution units branch predictors control logic and buses;if the threads execution are each keeping one or more of those shared resources such as the execution unit or buses 100 busy then the hyperthreading will not improve throughput

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Pthread offer no performance increase when using virtual cores

In computer 1 the eigen3 performance is worse because the number of total processors virtual + physical - due to hyperthreading is greater than the number of physical processors

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Eigen3 matrix multiplication performance dependent of the processor?

First step would be to investigate why a processors with hyperthreading simultaneous multithreading could lead to poorer performances than a processors without this technology

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I need a short C programm that runs slower on a processor with HyperThreading than on one without it

More modern processors handle hyperthreading better than older processors

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8 logical threads at 4 cores will at a maximum run 4 times faster in parallel?

You may find that hyperthreading helps more on code that is using large amounts of memory so that the processors is regularly blocked on fetching from memory

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Hyper-threading Performance Comparison

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