Difference between revisions of "cpp/numeric/random/seed seq"
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{{cpp/title|seed_seq}} | {{cpp/title|seed_seq}} | ||
{{cpp/numeric/random/seed_seq/navbar}} | {{cpp/numeric/random/seed_seq/navbar}} | ||
| − | {{ddcl | header=random | | + | {{ddcl|header=random|since=c++11| |
class seed_seq; | class seed_seq; | ||
}} | }} | ||
| − | {{tt|std::seed_seq}} consumes a sequence of integer-valued data and produces a requested number of unsigned integer values | + | {{tt|std::seed_seq}} consumes a sequence of integer-valued data and produces a requested number of 32-bit unsigned integer values, based on the consumed data. The produced values are distributed over the entire 32-bit range even if the consumed values are close. |
It provides a way to seed a large number of random number engines or to seed a generator that requires a lot of entropy, given a small seed or a poorly distributed initial seed sequence. | It provides a way to seed a large number of random number engines or to seed a generator that requires a lot of entropy, given a small seed or a poorly distributed initial seed sequence. | ||
| − | {{ | + | {{ttt|std::seed_seq}} meets the requirements of {{named req|SeedSequence}}. |
| − | === | + | ===Nested types=== |
{{dsc begin}} | {{dsc begin}} | ||
| − | {{dsc hitem | | + | {{dsc hitem|Type|Definition}} |
| − | {{dsc | {{tt|result_type}} | {{lc|std::uint_least32_t}}}} | + | {{dsc|{{tt|result_type}}|{{lc|std::uint_least32_t}}}} |
| + | {{dsc end}} | ||
| + | |||
| + | ===Data members=== | ||
| + | {{dsc begin}} | ||
| + | {{dsc hitem|Member|Description}} | ||
| + | {{dsc expos mem obj|spec={{c/core|std::vector<result_type>}}|v|id=v|the underlying seed sequence}} | ||
{{dsc end}} | {{dsc end}} | ||
===Member functions=== | ===Member functions=== | ||
{{dsc begin}} | {{dsc begin}} | ||
| − | {{dsc mem ctor | cpp/numeric/random/seed_seq/seed_seq | constructs and seeds the std::seed_seq object}} | + | {{dsc mem ctor|cpp/numeric/random/seed_seq/seed_seq|constructs and seeds the {{tt|std::seed_seq}} object}} |
| − | {{dsc mem fun | nolink=true | operator{{=}} | + | {{dsc mem fun|nolink=true|operator{{=}}|notes={{cmark|deleted}}|{{tt|std::seed_seq}} is not assignable}} |
| − | {{dsc mem fun | cpp/numeric/random/seed_seq/generate | calculates the bias-eliminated, evenly distributed 32-bit values}} | + | {{dsc mem fun|cpp/numeric/random/seed_seq/generate|calculates the bias-eliminated, evenly distributed 32-bit values}} |
| − | {{dsc mem fun | cpp/numeric/random/seed_seq/size | obtains the number of 32-bit values | + | {{dsc mem fun|cpp/numeric/random/seed_seq/size|obtains the number of stored 32-bit values}} |
| − | {{dsc mem fun | cpp/numeric/random/seed_seq/param | | + | {{dsc mem fun|cpp/numeric/random/seed_seq/param|copies all stored 32-bit values}} |
{{dsc end}} | {{dsc end}} | ||
===Example=== | ===Example=== | ||
| − | |||
{{example | {{example | ||
| − | + | |code= | |
| − | + | #include <cstdint> | |
| − | #include < | + | |
#include <iostream> | #include <iostream> | ||
| + | #include <random> | ||
int main() | int main() | ||
{ | { | ||
| − | std::seed_seq seq | + | std::seed_seq seq{1, 2, 3, 4, 5}; |
std::vector<std::uint32_t> seeds(10); | std::vector<std::uint32_t> seeds(10); | ||
seq.generate(seeds.begin(), seeds.end()); | seq.generate(seeds.begin(), seeds.end()); | ||
| − | for(std::uint32_t n : seeds) | + | for (std::uint32_t n : seeds) |
std::cout << n << '\n'; | std::cout << n << '\n'; | ||
} | } | ||
| − | + | |p=true | |
| + | |output= | ||
4204997637 | 4204997637 | ||
4246533866 | 4246533866 | ||
| Line 52: | Line 58: | ||
3904109078 | 3904109078 | ||
1534123438 | 1534123438 | ||
| − | 1495905678 | + | 1495905678 |
}} | }} | ||
| − | + | {{langlinks|de|es|fr|it|ja|pt|ru|zh}} | |
| − | + | ||
| − | + | ||
| − | + | ||
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Latest revision as of 23:36, 22 October 2024
| Defined in header <random>
|
||
| class seed_seq; |
(since C++11) | |
std::seed_seq consumes a sequence of integer-valued data and produces a requested number of 32-bit unsigned integer values, based on the consumed data. The produced values are distributed over the entire 32-bit range even if the consumed values are close.
It provides a way to seed a large number of random number engines or to seed a generator that requires a lot of entropy, given a small seed or a poorly distributed initial seed sequence.
std::seed_seq meets the requirements of SeedSequence.
Contents |
[edit] Nested types
| Type | Definition |
result_type
|
std::uint_least32_t |
[edit] Data members
| Member | Description |
std::vector<result_type> v
|
the underlying seed sequence (exposition-only member object*) |
[edit] Member functions
constructs and seeds the std::seed_seq object (public member function) | |
| operator= [deleted] |
std::seed_seq is not assignable (public member function) |
| calculates the bias-eliminated, evenly distributed 32-bit values (public member function) | |
| obtains the number of stored 32-bit values (public member function) | |
| copies all stored 32-bit values (public member function) |
[edit] Example
Run this code
#include <cstdint> #include <iostream> #include <random> int main() { std::seed_seq seq{1, 2, 3, 4, 5}; std::vector<std::uint32_t> seeds(10); seq.generate(seeds.begin(), seeds.end()); for (std::uint32_t n : seeds) std::cout << n << '\n'; }
Possible output:
4204997637 4246533866 1856049002 1129615051 690460811 1075771511 46783058 3904109078 1534123438 1495905678
