std::subtract_with_carry_engine

From cppreference.com

Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros(C++20)
Language support library
Concepts library(C++20)
Diagnostics library
Memory management library
Metaprogramming library(C++11)
General utilities library
Containers library
Iterators library
Ranges library(C++20)
Algorithms library
Strings library
Text processing library
Numerics library
Date and time library
Input/output library
Filesystem library(C++17)
Concurrency support library(C++11)
Execution control library(C++26)
Technical specifications
Symbols index
External libraries

[edit]

Numerics library

Common mathematical functions

Mathematical special functions(C++17)

Mathematical constants(C++20)

Basic linear algebra algorithms(C++26)

Data-parallel types (SIMD)(C++26)

Floating-point environment(C++11)

Complex numbers

Numeric array (valarray)

Pseudo-random number generation

Bit manipulation(C++20)

Saturation arithmetic(C++26)

(C++17)

(C++17)

(C++20)

(C++20)

Generic numeric operations

iota (C++11)
ranges::iota (C++23)
accumulate
inner_product
adjacent_difference
partial_sum

reduce (C++17)
transform_reduce (C++17)
inclusive_scan (C++17)
exclusive_scan (C++17)
transform_inclusive_scan (C++17)
transform_exclusive_scan (C++17)

C-style checked integer arithmetic

ckd_add (C++26)
ckd_sub (C++26)

ckd_mul (C++26)

[edit]

Pseudo-random number generation

Uniform random bit generators

uniform_random_bit_generator

(C++20)

Random number engines

linear_congruential_engine

(C++11)

mersenne_twister_engine

(C++11)

subtract_with_carry_engine

(C++11)

philox_engine

(C++26)

Random number engine adaptors

discard_block_engine

(C++11)

independent_bits_engine

(C++11)

shuffle_order_engine

(C++11)

Predefined random number generators

Non-deterministic random numbers

(C++11)

(C++11)

(C++11)

Random number algorithms

ranges::generate_random

(C++26)

Random number distributions
Uniform distributions
uniform_int_distribution (C++11)
uniform_real_distribution (C++11)
generate_canonical (C++11)
Bernoulli distributions
bernoulli_distribution (C++11)
binomial_distribution (C++11)
negative_binomial_distribution (C++11)
geometric_distribution (C++11)
Poisson distributions
poisson_distribution (C++11)
exponential_distribution (C++11)
gamma_distribution (C++11)
weibull_distribution (C++11)
extreme_value_distribution (C++11)
Normal distributions
normal_distribution (C++11)
lognormal_distribution (C++11)
chi_squared_distribution (C++11)
cauchy_distribution (C++11)
fisher_f_distribution (C++11)
student_t_distribution (C++11)
Sampling distributions
discrete_distribution (C++11)
piecewise_constant_distribution (C++11)
piecewise_linear_distribution (C++11)

[edit]

std::subtract_with_carry_engine

Member functions
subtract_with_carry_engine::subtract_with_carry_engine
subtract_with_carry_engine::seed
Generation
subtract_with_carry_engine::operator()
subtract_with_carry_engine::discard
Characteristics
subtract_with_carry_engine::min
subtract_with_carry_engine::max
Non-member functions
operator==operator!= (C++11)(C++11)(until C++20)
operator<<operator>> (C++11)(C++11)

[edit]

Defined in header`<random>`
template< class UIntType, std::size_t w,std::size_t s,std::size_t r >class subtract_with_carry_engine;		(since C++11)

Is a random number engine that usessubtract with carry algorithm.

[edit]Template parameters

UIntType	-	The result type generated by the generator. The effect is undefined if this is not one ofunsignedshort,unsignedint,unsignedlong, orunsignedlonglong.
w	-	the word size, in bits, of the state sequence
s	-	the short lag
r	-	the long lag

Ifw is not in[1, std::numeric_limits<UIntType>::digits], ors is not in[1, r), the program is ill-formed.

[edit]Generator properties

Thesize of the states ofsubtract_with_carry_engine is\(\scriptsize O(r)\)O(r), each of them consists of two parts:

A sequenceX ofr integer values, where each value is in[0, 2w
).
An integerc (known as thecarry ), whose value is either0 or1.

Given that\(\scriptsize X_j\)Xj stands for the\(\scriptsize j\mod r\)j mod rth value (starting from 0) ofX, thetransition algorithm ofsubtract_with_carry_engine (\(\scriptsize TA(x_i)\)TA(xi)) is defined as follows:

LetY be\(\scriptsize X_{i-s}-X_{i-r}-c\)Xi-s-Xi-r-c.
Lety be\(\scriptsize Y\mod 2^w\)Y mod 2w
, and set\(\scriptsize X_i\)Xi toy.
IfY is negative, setc to1, otherwise setc to0.

Thegeneration algorithm ofsubtract_with_carry_engine is\(\scriptsize GA(x_i) = y\)GA(xi) = y, wherey is the value produced in step 2 of the transition algorithm.

[edit]Predefined specializations

The following specializations define the random number engine with two commonly used parameter sets:

Defined in header`<random>`
Type	Definition
`ranlux24_base`(C++11)	std::subtract_with_carry_engine<std::uint_fast32_t,24,10,24>[edit]
`ranlux48_base`(C++11)	std::subtract_with_carry_engine<std::uint_fast64_t,48,5,12>[edit]

[edit]Nested types

Type	Definition
`result_type`	`UIntType`

[edit]Data members

constexprstd::size_t word_size [static]	w (public static member constant)
constexprstd::size_t short_lag [static]	s (public static member constant)
constexprstd::size_t long_lag [static]	r (public static member constant)
constexprstd::uint_least32_t default_seed [static]	19780503u (public static member constant)

[edit]Member functions

Construction and Seeding
(constructor)	constructs the engine (public member function)[edit]
seed	sets the current state of the engine (public member function)[edit]
Generation
operator()	advances the engine's state and returns the generated value (public member function)[edit]
discard	advances the engine's state by a specified amount (public member function)[edit]
Characteristics
min [static]	gets the smallest possible value in the output range (public static member function)[edit]
max [static]	gets the largest possible value in the output range (public static member function)[edit]

[edit]Non-member functions

operator==operator!= (C++11)(C++11)(removed in C++20)	compares the internal states of two pseudo-random number engines (function)[edit]

operator<<operator>> (C++11)	performs stream input and output on pseudo-random number engine (function template)[edit]