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Tony0945
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Joined: 25 Jul 2006
Posts: 5127
Location: Illinois, USA
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 Posted: Sun Jan 12, 2020 5:44 pm Post subject: Some portage timings |
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| Code: | Trantor ~ # time emerge -puvND @world
These are the packages that would be merged, in order:
Calculating dependencies... done!
Total: 0 packages, Size of downloads: 0 KiB
real 1m11.566s
user 1m11.198s
sys 0m0.317s
Trantor ~ # time emerge -puvND @world --backtrack=0
These are the packages that would be merged, in order:
Calculating dependencies... done!
Total: 0 packages, Size of downloads: 0 KiB
real 0m33.134s
user 0m32.776s
sys 0m0.319s
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Dependency resolution is often said to be NP-hard. If so, breaking it into two smaller sets should reduce that total non-polynomial time. But it doesn't.
| Code: | Trantor ~ # time emerge -puvND @system
These are the packages that would be merged, in order:
Calculating dependencies... done!
Total: 0 packages, Size of downloads: 0 KiB
real 0m34.998s
user 0m34.744s
sys 0m0.215s
Trantor ~ # time emerge -puvND @selected
These are the packages that would be merged, in order:
Calculating dependencies... done!
Total: 0 packages, Size of downloads: 0 KiB
real 1m11.315s
user 1m10.897s
sys 0m0.365s
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This was run on a small system with a slow processor (FM2+ APU)
| Code: | Packages installed: 751
Packages in world: 128
Packages in system: 43
Required packages: 748
Number to remove: 3
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NeddySeagoon
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Joined: 05 Jul 2003
Posts: 54304
Location: 56N 3W
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| Posted: Sun Jan 12, 2020 6:17 pm Post subject: |
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Tony0945,
You cannot break dependency resolution down into subsets, so it won't scale like that.
You would need to know in advance a list of packages to exclude from each subset. To get that exclusion list you need to run dependency resolution on the entire tree.
_________________
Regards,
NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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Tony0945
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Joined: 25 Jul 2006
Posts: 5127
Location: Illinois, USA
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| Posted: Sun Jan 12, 2020 7:03 pm Post subject: |
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| Isn't selected just world minus system? |
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Tony0945
Watchman
Joined: 25 Jul 2006
Posts: 5127
Location: Illinois, USA
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| Posted: Sun Jan 12, 2020 7:05 pm Post subject: |
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| The --backtrack=0 looks promising for simple updates. Probably fails when major changes like gtk+, qt, python, perl are made. But for just occasional userland package updates it's probably good. |
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NeddySeagoon
Administrator
Joined: 05 Jul 2003
Posts: 54304
Location: 56N 3W
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| Posted: Sun Jan 12, 2020 7:12 pm Post subject: |
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Tony0945,
It still has to calculate the entire dependency tree.
e.g. gcc is in @system.
A package can depend on >=sys-devel/gcc-9.2.0 or any other system set package, a @system package with a particular USE flag on/off.
Try and again with your world file and USE settings moved out of the way.
You get quite different results.
_________________
Regards,
NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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