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Difference between revisions of "cpp/numeric/random/seed seq"

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< cpp‎ | numeric‎ | random
m (Text replace - "{{tdcl list begin" to "{{dcl list begin")
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{{cpp/title|seed_seq}}
 
{{cpp/title|seed_seq}}
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{{cpp/numeric/random/uniform_real_distribution/sidebar}}
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{{cpp/numeric/random/seed_seq/navbar}}
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{{ddcl | header=random | notes={{mark since c++11}} | 1=
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{{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|i}}, {{math|0 ≤ i < 2{{su|p=32}}}}, based on the consumed data. The produced values are distributed over the entire 32-bit range even if the consumed values are close.
+
{{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.
  
−
{{tt|std::seed_seq}} meets the requirements of {{concept|SeedSequence}}.
+
{{ttt|std::seed_seq}} meets the requirements of {{named req|SeedSequence}}.
  
−
===Member types===
+
===Nested types===
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{{dcl list begin}}
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{{dsc begin}}
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{{tdcl list hitem | Member type | Definition}}
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{{dsc hitem|Type|Definition}}
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{{tdcl list item | {{tt|result_type}} | {{c|uint_least32_t}}}}
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{{dsc|{{tt|result_type}}|{{lc|std::uint_least32_t}}}}
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{{tdcl list end}}
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{{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}}
  
 
===Member functions===
 
===Member functions===
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{{dcl list begin}}
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{{dsc begin}}
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{{dcl list mem ctor | cpp/numeric/random/seed_seq/seed_seq | constructs and seeds the std::seed_seq object}}
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{{dsc mem ctor|cpp/numeric/random/seed_seq/seed_seq|constructs and seeds the {{tt|std::seed_seq}} object}}
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{{dcl list mem fun | nolink=true | operator{{=}} | not copy-assignable | notes={{mark|deleted}}}}
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{{dsc mem fun|nolink=true|operator{{=}}|notes={{cmark|deleted}}|{{tt|std::seed_seq}} is not assignable}}
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{{dcl list mem fun | cpp/numeric/random/seed_seq/generate | calculates the bias-eliminated, evenly distributed 32-bit values}}
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{{dsc mem fun|cpp/numeric/random/seed_seq/generate|calculates the bias-eliminated, evenly distributed 32-bit values}}
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{{dcl list mem fun | cpp/numeric/random/seed_seq/size | obtains the number of 32-bit values stored in std::seed_seq }}
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{{dsc mem fun|cpp/numeric/random/seed_seq/size|obtains the number of stored 32-bit values}}
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{{dcl list mem fun | cpp/numeric/random/seed_seq/param | obtains the 32-bit values stored in std::seed_seq}}
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{{dsc mem fun|cpp/numeric/random/seed_seq/param|copies all stored 32-bit values}}
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{{dcl list end}}
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{{dsc end}}
  
 
===Example===
 
===Example===
−
 
 
{{example
 
{{example
−
|
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|code=
−
| code=
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#include <cstdint>
−
#include <random>
+
 
#include <iostream>
 
#include <iostream>
 +
#include <random>
 +
 
int main()
 
int main()
 
{
 
{
−
     std::seed_seq seq({1,2,3,4,5});
+
     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';
 
}
 
}
−
| output=
+
|p=true
−
3890079369
+
|output=
−
567513683
+
4204997637
−
1868094942
+
4246533866
−
738085780
+
1856049002
−
2849436979
+
1129615051
−
1267185068
+
690460811
−
3817490445
+
1075771511
−
2911200628
+
46783058
−
2374022914
+
3904109078
−
1233116465
+
1534123438
 +
1495905678
 
}}
 
}}
 +
 +
{{langlinks|de|es|fr|it|ja|pt|ru|zh}}

Latest revision as of 23:36, 22 October 2024

 
C++
 
Numerics library
Common mathematical functions
Mathematical special functions (C++17)
Mathematical constants (C++20)
Basic linear algebra algorithms (C++26)
Floating-point environment (C++11)
Complex numbers
Numeric array (valarray)
Pseudo-random number generation
Factor operations
(C++17)
(C++17)
Interpolations
(C++20)
(C++20)
Saturation arithmetic
(C++26)
(C++26)
(C++26)
(C++26)
(C++26)

Generic numeric operations
Bit operations
(C++20)    
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++23)
(C++20)
 
Pseudo-random number generation
 
std::seed_seq
 
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
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