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Fix #9535: Maintain a reverse dependency map of network content #9538

merged 1 commit into from Sep 9, 2021


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@JGRennison JGRennison commented Sep 4, 2021

Motivation / Problem

This fixes the performance issues in #9535 with dependency lookup when retrieving the content list from the content server.


Instead of iterating all content to find reverse dependencies, maintain an iteratively built reverse dependency map.
When a new content item arrives, instead of calling CheckDependencyState on all content items, only call it on the reverse tree dependencies of the newly received item.



Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

  • The bug fix is important enough to be backported? (label: 'backport requested')
  • This PR touches english.txt or translations? Check the guidelines
  • This PR affects the save game format? (label 'savegame upgrade')
  • This PR affects the GS/AI API? (label 'needs review: Script API')
    • ai_changelog.hpp, gs_changelog.hpp need updating.
    • The compatibility wrappers (compat_*.nut) need updating.
  • This PR affects the NewGRF API? (label 'needs review: NewGRF')

TrueBrain previously approved these changes Sep 5, 2021
@@ -82,6 +84,7 @@ class ClientNetworkContentSocketHandler : public NetworkContentSocketHandler, Co
bool Receive_SERVER_CONTENT(Packet *p) override;

ContentInfo *GetContent(ContentID cid);
const ContentInfo *GetContent(ContentID cid) const { return const_cast<ClientNetworkContentSocketHandler *>(this)->GetContent(cid); }
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@LordAro LordAro Sep 7, 2021

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Unless I'm missing something obvious, the existing GetContent method doesn't make any changes to the object and can be declared const without making this hacky extra function

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@JGRennison JGRennison Sep 7, 2021

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That's fixed now.

Fixes performance issues with dependency lookup when retrieving
content list from the content server.
LordAro approved these changes Sep 7, 2021
@TrueBrain TrueBrain merged commit 6e3d023 into OpenTTD:master Sep 9, 2021
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3 participants