Random functions (C++ SDK)#

Random functions request both structured and unstructured randomness from the Antithesis platform. They are defined as part of the Antithesis C++ SDK.

These functions should not be used to seed a conventional PRNG, and should not have their return values stored and used to make a decision at a later time. Doing either of these things makes it much harder for the Antithesis platform to control the history of your program’s execution, and also makes it harder for Antithesis to learn which inputs, provided at which times, are most fruitful. Instead, you should call a function from the random package every time your program or workload needs to make a decision—at the moment that you need to make the decision.

These functions are also safe to call outside the Antithesis environment, where they will fall back on values from the standard library’s random. If you want to override this default behavior, then #define ANTITHESIS_RANDOM_OVERRIDE. If this is defined, then the SDK will use the provided function when run locally. (This setting is ignored when run in the Antithesis environment.)


To use this override, define ANTITHESIS_RANDOM_OVERRIDE before including antithesis_sdk.h:

 #include "antithesis_sdk.h"

  // ...

 uint64_t my_random() {
     // Do something and return a random number


Get random
uint64_t get_random()

Returns a uint64_t value chosen by Antithesis. You should not store this value or use it to seed a PRNG, but should use it immediately.

The function is called using the Antithesis namespace: antithesis::get_random()

Random choice
template <typename Iter>
Iter random_choice(Iter begin, Iter end)

Returns a randomly chosen item from a list of options. You should not store this value but should use it immediately. Internally, this function gets its randomness from get_random().

This function is not purely for convenience. Signaling to the Antithesis platform that you intend to use a random value in a structured way enables it to provide more interesting choices over time.

The function is called using the Antithesis namespace: antithesis::random_choice(begin, end)

Template parameters


Iter should be a random-access iterator type.


std::string in {"ABCDEFGHIJK"};
char random_character = *antithesis::random_choice(in.begin(), in.end());