Each instance has 30 variables. Each variable’s length is constrained randomly from 0 to X.

Each instance has 30 variables. Each variable’s length is constrained randomly from 0 to X.

Each instance has X variables, and Y random unique binary concats of those variables.

Each instance is a right-heavy concat tree of depth X, equal to the string "solution".

Each instance is a right-heavy concat tree of depth X, equal to the string "solution".

Each instance is a balanced concat tree of depth X, equal to the string "solution".

Each instance is a right-heavy concat tree of depth 30, equal to the string "solution", followed by X extracts of 1 character each, from a random index Y.

Each instance is a right-heavy concat tree of depth 30, equal to the string "solution", followed by X extracts of 1 character each, from a random index Y.

Each instance is an equation of the form a.V = V.b, where V is a concatenation of X variables.

Each instance is an equation of the form a.V = V.b, where V is a concatenation of X variables.

Each instance tests whether a variable belongs to a random regex. The regex is a concatenation of X random regex terms of depth 2.

Each instance tests whether a variable belongs to a random regex. The regex is a concatenation of X random regex terms of depth 2.

Each instance tests whether a variable belongs to a random regex. The regex is a concatenation of 2 random regex terms of depth X. The variable is at least 15 characters long.

Each instance tests whether a variable is in X regexes. Each regex is a concatenation of 10 terms of depth 2.

Each instance tests whether a variable is in one regex but not another. Each regex is a concatenation of X terms of depth 2.

Each instance tests whether a variable is in a regex, and constrains the variable to a minimum length of X. The regex contains 10 terms, each of depth 2.

Each instance is a problem of the form V = a.Y = b.Y where V is a variable.