msgid "" msgstr "" "Project-Id-Version: English (Boost Unordered Translation (zh_Hans))\n" "Report-Msgid-Bugs-To: \n" "POT-Creation-Date: 2026-06-07 00:01+0000\n" "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n" "Last-Translator: FULL NAME \n" "Language-Team: English \n" "Language: en\n" "MIME-Version: 1.0\n" "Content-Type: text/plain; charset=UTF-8\n" "Content-Transfer-Encoding: 8bit\n" "Plural-Forms: nplurals=2; plural=n != 1;\n" "X-Generator: Weblate 2026.5\n" #: :3 #, read-only, safe-html, strict-same msgid ":idprefix: rationale_" msgstr ":idprefix: rationale_" #: :5 #, read-only, safe-html, strict-same msgid "= Implementation Rationale" msgstr "= Implementation Rationale" #: :7 #, read-only, safe-html, strict-same msgid "Closed-addressing Containers" msgstr "Closed-addressing Containers" #: :9 #, read-only, safe-html, strict-same msgid "" "`boost::unordered_[multi]set` and `boost::unordered_[multi]map` adhere to " "the standard requirements for unordered associative containers, so the " "interface was fixed. But there are still some implementation decisions to " "make. The priorities are conformance to the standard and portability." msgstr "" "`boost::unordered_[multi]set` and `boost::unordered_[multi]map` adhere to " "the standard requirements for unordered associative containers, so the " "interface was fixed. But there are still some implementation decisions to " "make. The priorities are conformance to the standard and portability." #: :15 #, read-only, safe-html, strict-same msgid "" "The http://en.wikipedia.org/wiki/Hash_table[Wikipedia article on hash " "tables^] has a good summary of the implementation issues for hash tables in " "general." msgstr "" "The http://en.wikipedia.org/wiki/Hash_table[Wikipedia article on hash " "tables^] has a good summary of the implementation issues for hash tables in " "general." #: :18 #, read-only, safe-html, strict-same msgid "Data Structure" msgstr "Data Structure" #: :20 #, read-only, safe-html, strict-same msgid "" "By specifying an interface for accessing the buckets of the container the " "standard pretty much requires that the hash table uses closed addressing." msgstr "" "By specifying an interface for accessing the buckets of the container the " "standard pretty much requires that the hash table uses closed addressing." #: :23 #, read-only, safe-html, strict-same msgid "" "It would be conceivable to write a hash table that uses another method. For " "example, it could use open addressing, and use the lookup chain to act as a " "bucket but there are some serious problems with this:" msgstr "" "It would be conceivable to write a hash table that uses another method. For " "example, it could use open addressing, and use the lookup chain to act as a " "bucket but there are some serious problems with this:" #: :27 #, read-only, safe-html, strict-same msgid "The standard requires that pointers to elements aren't invalidated, so" msgstr "The standard requires that pointers to elements aren't invalidated, so" #: :28 #, read-only, safe-html, strict-same msgid "" "the elements can't be stored in one array, but will need a layer of " "indirection instead - losing the efficiency and most of the memory gain, the " "main advantages of open addressing." msgstr "" "the elements can't be stored in one array, but will need a layer of " "indirection instead - losing the efficiency and most of the memory gain, the " "main advantages of open addressing." #: :31 #, read-only, safe-html, strict-same msgid "Local iterators would be very inefficient and may not be able to" msgstr "Local iterators would be very inefficient and may not be able to" #: :32 #, read-only, safe-html, strict-same msgid "meet the complexity requirements." msgstr "meet the complexity requirements." #: :33 #, read-only, safe-html, strict-same msgid "" "There are also the restrictions on when iterators can be invalidated. Since" msgstr "" "There are also the restrictions on when iterators can be invalidated. Since" #: :34 #, read-only, safe-html, strict-same msgid "" "open addressing degrades badly when there are a high number of collisions " "the restrictions could prevent a rehash when it's really needed. The maximum " "load factor could be set to a fairly low value to work around this - but the " "standard requires that it is initially set to 1.0." msgstr "" "open addressing degrades badly when there are a high number of collisions " "the restrictions could prevent a rehash when it's really needed. The maximum " "load factor could be set to a fairly low value to work around this - but the " "standard requires that it is initially set to 1.0." #: :38 #, read-only, safe-html, strict-same msgid "And since the standard is written with a eye towards closed" msgstr "And since the standard is written with a eye towards closed" #: :39 #, read-only, safe-html, strict-same msgid "" "addressing, users will be surprised if the performance doesn't reflect that." msgstr "" "addressing, users will be surprised if the performance doesn't reflect that." #: :41 #, read-only, safe-html, strict-same msgid "So closed addressing is used." msgstr "So closed addressing is used." #: :43 #, read-only, safe-html, strict-same msgid "Number of Buckets" msgstr "Number of Buckets" #: :45 #, read-only, safe-html, strict-same msgid "" "There are two popular methods for choosing the number of buckets in a hash " "table. One is to have a prime number of buckets, another is to use a power " "of 2." msgstr "" "There are two popular methods for choosing the number of buckets in a hash " "table. One is to have a prime number of buckets, another is to use a power " "of 2." #: :49 #, read-only, safe-html, strict-same msgid "" "Using a prime number of buckets, and choosing a bucket by using the modulus " "of the hash function's result will usually give a good result. The downside " "is that the required modulus operation is fairly expensive. This is what the " "containers used to do in most cases." msgstr "" "Using a prime number of buckets, and choosing a bucket by using the modulus " "of the hash function's result will usually give a good result. The downside " "is that the required modulus operation is fairly expensive. This is what the " "containers used to do in most cases." #: :54 #, read-only, safe-html, strict-same msgid "" "Using a power of 2 allows for much quicker selection of the bucket to use, " "but at the expense of losing the upper bits of the hash value. For some " "specially designed hash functions it is possible to do this and still get a " "good result but as the containers can take arbitrary hash functions this " "can't be relied on." msgstr "" "Using a power of 2 allows for much quicker selection of the bucket to use, " "but at the expense of losing the upper bits of the hash value. For some " "specially designed hash functions it is possible to do this and still get a " "good result but as the containers can take arbitrary hash functions this " "can't be relied on." #: :60 #, read-only, safe-html, strict-same msgid "" "To avoid this a transformation could be applied to the hash function, for an " "example see http://web.archive.org/web/20121102023700/http://" "www.concentric.net/~Ttwang/tech/inthash.htm[Thomas Wang's article on integer " "hash functions^]. Unfortunately, a transformation like Wang's requires " "knowledge of the number of bits in the hash value, so it was only used when " "`size_t` was 64 bit." msgstr "" "To avoid this a transformation could be applied to the hash function, for an " "example see http://web.archive.org/web/20121102023700/http://" "www.concentric.net/~Ttwang/tech/inthash.htm[Thomas Wang's article on integer " "hash functions^]. Unfortunately, a transformation like Wang's requires " "knowledge of the number of bits in the hash value, so it was only used when " "`size_t` was 64 bit." #: :66 #, read-only, safe-html, strict-same msgid "" "Since release 1.79.0, https://en.wikipedia.org/wiki/" "Hash_function#Fibonacci_hashing[Fibonacci hashing] is used instead. With " "this implementation, the bucket number is determined by using `(h * m) >> " "(w - k)`, where `h` is the hash value, `m` is `2^w` divided by the golden " "ratio, `w` is the word size (32 or 64), and `2^k` is the number of buckets. " "This provides a good compromise between speed and distribution." msgstr "" "Since release 1.79.0, https://en.wikipedia.org/wiki/" "Hash_function#Fibonacci_hashing[Fibonacci hashing] is used instead. With " "this implementation, the bucket number is determined by using `(h * m) >> " "(w - k)`, where `h` is the hash value, `m` is `2^w` divided by the golden " "ratio, `w` is the word size (32 or 64), and `2^k` is the number of buckets. " "This provides a good compromise between speed and distribution." #: :73 #, read-only, safe-html, strict-same msgid "" "Since release 1.80.0, prime numbers are chosen for the number of buckets in " "tandem with sophisticated modulo arithmetic. This removes the need for " "\"mixing\" the result of the user's hash function as was used for release " "1.79.0." msgstr "" "Since release 1.80.0, prime numbers are chosen for the number of buckets in " "tandem with sophisticated modulo arithmetic. This removes the need for " "\"mixing\" the result of the user's hash function as was used for release " "1.79.0." #: :77 #, read-only, safe-html, strict-same msgid "Open-addresing Containers" msgstr "Open-addresing Containers" #: :79 #, read-only, safe-html, strict-same msgid "" "The C++ standard specification of unordered associative containers impose " "severe limitations on permissible implementations, the most important being " "that closed addressing is implicitly assumed. Slightly relaxing this " "specification opens up the possibility of providing container variations " "taking full advantage of open-addressing techniques." msgstr "" "The C++ standard specification of unordered associative containers impose " "severe limitations on permissible implementations, the most important being " "that closed addressing is implicitly assumed. Slightly relaxing this " "specification opens up the possibility of providing container variations " "taking full advantage of open-addressing techniques." #: :85 #, read-only, safe-html, strict-same msgid "" "The design of `boost::unordered_flat_set`/`unordered_node_set` and " "`boost::unordered_flat_map`/`unordered_node_map` has been guided by Peter " "Dimov's https://pdimov.github.io/articles/" "unordered_dev_plan.html[Development Plan for Boost.Unordered^]. We discuss " "here the most relevant principles." msgstr "" "The design of `boost::unordered_flat_set`/`unordered_node_set` and " "`boost::unordered_flat_map`/`unordered_node_map` has been guided by Peter " "Dimov's https://pdimov.github.io/articles/" "unordered_dev_plan.html[Development Plan for Boost.Unordered^]. We discuss " "here the most relevant principles." #: :89 #, read-only, safe-html, strict-same msgid "Hash Function" msgstr "Hash Function" #: :91 #, read-only, safe-html, strict-same msgid "" "Given its rich functionality and cross-platform interoperability, " "`boost::hash` remains the default hash function of open-addressing " "containers. As it happens, `boost::hash` for integral and other basic types " "does not possess the statistical properties required by open addressing; to " "cope with this, we implement a post-mixing stage:" msgstr "" "Given its rich functionality and cross-platform interoperability, " "`boost::hash` remains the default hash function of open-addressing " "containers. As it happens, `boost::hash` for integral and other basic types " "does not possess the statistical properties required by open addressing; to " "cope with this, we implement a post-mixing stage:" #: :97 #, read-only, safe-html, strict-same msgid "" "{nbsp}{nbsp}{nbsp}{nbsp} _a_ <- _h_ *mul* _C_, + {nbsp}{nbsp}{nbsp}{nbsp} " "_h_ <- *high*(_a_) *xor* *low*(_a_)," msgstr "" "{nbsp}{nbsp}{nbsp}{nbsp} _a_ <- _h_ *mul* _C_, + {nbsp}{nbsp}{nbsp}{nbsp} " "_h_ <- *high*(_a_) *xor* *low*(_a_)," #: :100 #, read-only, safe-html, strict-same msgid "" "where *mul* is an _extended multiplication_ (128 bits in 64-bit " "architectures, 64 bits in 32-bit environments), and *high* and *low* are the " "upper and lower halves of an extended word, respectively. In 64-bit " "architectures, _C_ is the integer part of 2^64^∕https://" "en.wikipedia.org/wiki/Golden_ratio[_φ_], whereas in 32 bits _C_ = " "0xE817FB2Du has been obtained from https://arxiv.org/abs/2001.05304[Steele " "and Vigna (2021)^]." msgstr "" "where *mul* is an _extended multiplication_ (128 bits in 64-bit " "architectures, 64 bits in 32-bit environments), and *high* and *low* are the " "upper and lower halves of an extended word, respectively. In 64-bit " "architectures, _C_ is the integer part of 2^64^∕https://" "en.wikipedia.org/wiki/Golden_ratio[_φ_], whereas in 32 bits _C_ = " "0xE817FB2Du has been obtained from https://arxiv.org/abs/2001.05304[Steele " "and Vigna (2021)^]." #: :105 #, read-only, safe-html, strict-same msgid "" "When using a hash function directly suitable for open addressing, post-" "mixing can be opted out of via a dedicated `link:../../../../container_hash/" "doc/html/hash.html#ref_hash_is_avalanchinghash[hash_is_avalanching]` trait. " "`boost::hash` specializations for string types are marked as avalanching." msgstr "" "When using a hash function directly suitable for open addressing, post-" "mixing can be opted out of via a dedicated `link:../../../../container_hash/" "doc/html/hash.html#ref_hash_is_avalanchinghash[hash_is_avalanching]` trait. " "`boost::hash` specializations for string types are marked as avalanching." #: :109 #, read-only, safe-html, strict-same msgid "Platform Interoperability" msgstr "Platform Interoperability" #: :111 #, read-only, safe-html, strict-same msgid "" "The observable behavior of `boost::unordered_flat_set`/`unordered_node_set` " "and `boost::unordered_flat_map`/`unordered_node_map` is deterministically " "identical across different compilers as long as their ``std::size_t``s are " "the same size and the user-provided hash function and equality predicate are " "also interoperable —this includes elements being ordered in exactly " "the same way for the same sequence of operations." msgstr "" "The observable behavior of `boost::unordered_flat_set`/`unordered_node_set` " "and `boost::unordered_flat_map`/`unordered_node_map` is deterministically " "identical across different compilers as long as their ``std::size_t``s are " "the same size and the user-provided hash function and equality predicate are " "also interoperable —this includes elements being ordered in exactly " "the same way for the same sequence of operations." #: :117 #, read-only, safe-html, strict-same msgid "" "Although the implementation internally uses SIMD technologies, such as " "https://en.wikipedia.org/wiki/SSE2[SSE2^] and https://en.wikipedia.org/wiki/" "ARM_architecture_family#Advanced_SIMD_(NEON)[Neon^], when available, this " "does not affect interoperatility. For instance, the behavior is the same for " "Visual Studio on an x64-mode Intel CPU with SSE2 and for GCC on an IBM s390x " "without any supported SIMD technology." msgstr "" "Although the implementation internally uses SIMD technologies, such as " "https://en.wikipedia.org/wiki/SSE2[SSE2^] and https://en.wikipedia.org/wiki/" "ARM_architecture_family#Advanced_SIMD_(NEON)[Neon^], when available, this " "does not affect interoperatility. For instance, the behavior is the same for " "Visual Studio on an x64-mode Intel CPU with SSE2 and for GCC on an IBM s390x " "without any supported SIMD technology." #: :122 #, read-only, safe-html, strict-same msgid "Concurrent Containers" msgstr "Concurrent Containers" #: :124 #, read-only, safe-html, strict-same msgid "" "The same data structure used by Boost.Unordered open-addressing containers " "has been chosen also as the foundation of `boost::concurrent_flat_set`/" "`boost::concurrent_node_set` and `boost::concurrent_flat_map`/" "`boost::concurrent_node_map`:" msgstr "" "The same data structure used by Boost.Unordered open-addressing containers " "has been chosen also as the foundation of `boost::concurrent_flat_set`/" "`boost::concurrent_node_set` and `boost::concurrent_flat_map`/" "`boost::concurrent_node_map`:" #: :128 #, read-only, safe-html, strict-same msgid "" "Open-addressing is faster than closed-addressing alternatives, both in non-" "concurrent and" msgstr "" "Open-addressing is faster than closed-addressing alternatives, both in non-" "concurrent and" #: :129 #, read-only, safe-html, strict-same msgid "concurrent scenarios." msgstr "concurrent scenarios." #: :130 #, read-only, safe-html, strict-same msgid "" "Open-addressing layouts are eminently suitable for concurrent access and " "modification" msgstr "" "Open-addressing layouts are eminently suitable for concurrent access and " "modification" #: :131 #, read-only, safe-html, strict-same msgid "" "with minimal locking. In particular, the metadata array can be used for " "implementations of lookup that are lock-free up to the last step of actual " "element comparison." msgstr "" "with minimal locking. In particular, the metadata array can be used for " "implementations of lookup that are lock-free up to the last step of actual " "element comparison." #: :133 #, read-only, safe-html, strict-same msgid "Layout compatibility with Boost.Unordered flat containers allows for" msgstr "Layout compatibility with Boost.Unordered flat containers allows for" #: :134 #, read-only, safe-html, strict-same msgid "" "xref:concurrent.adoc#concurrent_interoperability_with_non_concurrent_containers[fast " "transfer] of all elements between a concurrent container and its non-" "concurrent counterpart, and vice versa." msgstr "" "xref:concurrent.adoc#concurrent_interoperability_with_non_concurrent_containers[fast " "transfer] of all elements between a concurrent container and its non-" "concurrent counterpart, and vice versa." #: :138 #, read-only, safe-html, strict-same msgid "Hash Function and Platform Interoperability" msgstr "Hash Function and Platform Interoperability" #: :140 #, read-only, safe-html, strict-same msgid "" "Concurrent containers make the same decisions and provide the same " "guarantees as Boost.Unordered open-addressing containers with regards to " "xref:#rationale_hash_function[hash function defaults] and " "xref:#rationale_platform_interoperability[platform interoperability]." msgstr "" "Concurrent containers make the same decisions and provide the same " "guarantees as Boost.Unordered open-addressing containers with regards to " "xref:#rationale_hash_function[hash function defaults] and " "xref:#rationale_platform_interoperability[platform interoperability]."