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stl unordered_set如何设置初始bucket计数

unordered-set bucket unordered-map c c++

pdrak · 技术社区 · 13 年前

对于一个无序映射,我通过以下方式设置初始bucket计数:

unordered_map<string, dictionaryWord> dictionary(17749); // set initial bucket count to 17749

这种方式似乎不适用于无序集合。

/*line 150*/ unsigned char mask;
/*line 151*/ unordered_set<QueryID> query_id(109); // set initial bucket count to 109

编译器错误= 1) 数字常量之前应为标识符。 2) 应为,或。。。在数字常量之前。然后又犯了一堆错误

如何对一个未定义的集合做同样的事情?

非常感谢。

=================================================

如果我删除“(109)”,则没有错误

"/usr/bin/make" -f nbproject/Makefile-Release.mk QMAKE= SUBPROJECTS= .clean-conf
make[1]: Entering directory `/home/petros/NetBeansProjects/ACM_test'
rm -f -r build/Release
rm -f dist/Release/GNU-Linux-x86/acm_test
make[1]: Leaving directory `/home/petros/NetBeansProjects/ACM_test'


CLEAN SUCCESSFUL (total time: 80ms)

"/usr/bin/make" -f nbproject/Makefile-Release.mk QMAKE= SUBPROJECTS= .build-conf
make[1]: Entering directory `/home/petros/NetBeansProjects/ACM_test'
"/usr/bin/make"  -f nbproject/Makefile-Release.mk dist/Release/GNU-Linux-x86/acm_test
make[2]: Entering directory `/home/petros/NetBeansProjects/ACM_test'
mkdir -p build/Release/GNU-Linux-x86/ref_impl
rm -f build/Release/GNU-Linux-x86/ref_impl/core.o.d
g++ -pthread -O3 -std=c++11   -c -O2 -pthread -O3 -std=c++11 -MMD -MP -MF build/Release/GNU-Linux-x86/ref_impl/core.o.d -o build/Release/GNU-Linux-x86/ref_impl/core.o ref_impl/core.cpp
ref_impl/core.cpp:151:37: error: expected identifier before numeric constant
ref_impl/core.cpp:151:37: error: expected â,â or â...â before numeric constant
ref_impl/core.cpp: In function âErrorCode StartQuery(QueryID, const char*, MatchType, unsigned int)â:
ref_impl/core.cpp:250:24: error: expected unqualified-id before â(â token
ref_impl/core.cpp:250:38: error: missing template arguments before â)â token
ref_impl/core.cpp:250:39: error: expected â;â before âquery_idâ
ref_impl/core.cpp:257:19: error: âquery.SameQueries::query_idâ does not have class type
ref_impl/core.cpp: In function âErrorCode EndQuery(QueryID)â:
ref_impl/core.cpp:265:44: error: âqueries.std::vector<_Tp, _Alloc>::operator[]<SameQueries, std::allocator<SameQueries> >(((std::vector<SameQueries>::size_type)i)).SameQueries::query_idâ does not have class type
ref_impl/core.cpp:265:58: error: unable to deduce âconst autoâ from â<expression error>â
ref_impl/core.cpp:266:38: error: âqueries.std::vector<_Tp, _Alloc>::operator[]<SameQueries, std::allocator<SameQueries> >(((std::vector<SameQueries>::size_type)i)).SameQueries::query_idâ does not have class type
ref_impl/core.cpp:267:32: error: âqueries.std::vector<_Tp, _Alloc>::operator[]<SameQueries, std::allocator<SameQueries> >(((std::vector<SameQueries>::size_type)i)).SameQueries::query_idâ does not have class type
ref_impl/core.cpp:268:36: error: âqueries.std::vector<_Tp, _Alloc>::operator[]<SameQueries, std::allocator<SameQueries> >(((std::vector<SameQueries>::size_type)i)).SameQueries::query_idâ does not have class type
ref_impl/core.cpp: In function âvoid* TaskCode(void*)â:
ref_impl/core.cpp:463:41: error: âquer.SameQueries::query_idâ does not have class type
ref_impl/core.cpp:463:48: error: unable to deduce âautoâ from â<expression error>â
ref_impl/core.cpp:463:70: error: âquer.SameQueries::query_idâ does not have class type
make[2]: *** [build/Release/GNU-Linux-x86/ref_impl/core.o] Error 1
make[2]: Leaving directory `/home/petros/NetBeansProjects/ACM_test'
make[1]: *** [.build-conf] Error 2
make[1]: Leaving directory `/home/petros/NetBeansProjects/ACM_test'
make: *** [.build-impl] Error 2


BUILD FAILED (exit value 2, total time: 1s)

3 回复 | 直到 13 年前

pdrak 13 年前

它在一个结构中。 应该是:

unordered_set<QueryID> query_id = unordered_set<QueryID>(109);

非常感谢。

NPE 13 年前

我怀疑桶数是在转移注意力。看起来像 QueryID 不可见。

scones 13 年前

我怀疑你 QueryID 没有标准的构造函数 QueryID::QueryID() { std::cout << "foo!" }; 因此无序集合不知道如何使用空QueryID进行预填充。

尝试添加一个。

或者,您可以使用第二个参数来设置每个预构建bucket要使用的默认数据。

参考文献: http://en.cppreference.com/w/cpp/container/unordered_set/unordered_set