Using reserve for optimize inserts and minor fixes #723
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plugins/arclite/archive.hpp
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| @@ -169,7 +169,7 @@ class ArcAPI { | |||
| static const ArcCodecs& codecs() { | |||
| return get()->arc_codecs; | |||
| } | |||
| static size_t Count7zCodecs() { | |||
| static const size_t Count7zCodecs() { | |||
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const is useless on return types.
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fix it here d832463
plugins/arclite/plugin.cpp
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| @@ -702,8 +702,9 @@ class Plugin | |||
| }); | |||
| const auto error_log = std::make_shared<ErrorLog>(); | |||
| size_t im = 0, nm = matched_indices.size(); | |||
| std::vector<UInt32> indices; | |||
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This changes the semantics: previously on each iteration the vector was recreated, now it's outside the loop and will accumulate all the values.
If you want to optimize here, add indices.clear() to the loop.
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u ar absolutely right, I have changed original behavior function.
fix it here d832463
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@alabuzhev, |
plugins/arclite/archive.cpp
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| @@ -233,6 +233,7 @@ class MyCompressCodecsInfo : public ICompressCodecsInfo, public IHashers, privat | |||
| } | |||
| if (arc_lib.ComHashers) { | |||
| UInt32 numHashers = arc_lib.ComHashers->GetNumHashers(); | |||
| hashers_.reserve(numHashers); | |||
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Thinking about it, all this code is a part of a bigger loop, and calling reserve in a loop is a known antipattern: it is too easy to pessimise exponential growth down to linear.
I suggest leaving it as is, it's not like like this place is a bottleneck anyway.
plugins/arclite/archive.cpp
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| @@ -400,6 +401,7 @@ void ArcAPI::load_codecs(const std::wstring& path) { | |||
| const auto& add_hashers = [this](ArcLib &arc_lib, size_t lib_index) { | |||
| if (arc_lib.ComHashers) { | |||
| UInt32 numHashers = arc_lib.ComHashers->GetNumHashers(); | |||
| arc_hashers.reserve(numHashers); | |||
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Same as above: add_hashers is calling from a for loop below, and then again from a while loop.
reserveing here would effectively kill exponential growth,
plugins/arclite/plugin.cpp
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| while (im < nm) { | ||
| std::vector<UInt32> indices; | ||
| if (!indices.empty()) |
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This condition is redundant, clear checks it internally.
Signed-off-by: German Semenov <[email protected]>
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Summary
Useful changes, additional insert were found at
emplace_back, but memory didnt allocated for last insert after loop.