mirror of https://github.com/OpenTTD/OpenTTD.git
31 lines
1.6 KiB
Markdown
31 lines
1.6 KiB
Markdown
# Some clarifications about the link graph
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`InitializeLinkGraphs` joins all threads, so if the game is abandoned
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with some threads still running, they're joined as soon as the next game
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(possibly the title game) is started. See also `InitializeGame`.
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The MCF (multi-commodity flow) algorithm can be quite CPU-hungry as it's
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NP-hard and takes exponential time (though with a very small constant
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factor) in the number of nodes.
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This is why it is run in a separate thread where possible. However after
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some time the thread is joined and if it hasn't finished by then the game
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will hang. This problem gets worse if we are running on a platform without
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threads. However, as those are usually the ones with less CPU power I
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assume the contention for the CPU would make the game hard to play even
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with threads or even without cargodist (autosave ...). I might be wrong,
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but I won't put any work into this before someone shows me some problem.
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You can configure the link graph recalculation time. A link graph
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recalculation time of X days means that each link graph job has X days
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to run before it is joined. The downside is that the flow stats won't be
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updated before the job is finished and thus a high value means less
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updates and longer times until changes in capacities are accounted for.
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If you play a very large map with a complicated link graph you may want to
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raise the time setting to avoid lags. The same holds for systems with slow
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CPUs.
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Another option to avoid excessive lags is to reduce the accuracy of link
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graph calculations. Generally the accuracy is inversely correlated to the
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CPU requirements of the MCF algorithm.
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