1		:- multifile generate/2.
2
3		% shrinking of all mutations defined in mutation.pl
4
5		:- use_module(library(lists),[is_list/1,maplist/2]).
6		:- use_module(library(random),[random_permutation/2,random_member/2,random/3]).
7		:- use_module(library(clpfd)).
8
9		% ProB ast integer expressions
10		generate(mutation(Expression:prob_ast_int_expr),NewExpression) :-
11		\+is_list(Expression) ,
12		random_int_expr_mutation(Expression,NewExpression).
13		% mutation of a list of integer expressions
14		generate(mutation(Expressions:prob_ast_int_expr),NewExpression) :-
15		% well-definedness problem with concatenation using div and modulo, division by zero
16		% power_of also deprecated because of integer overflow
17		concatenate_ast(Expressions,[add,minus,multiplication],Expression) ,
18		random_int_expr_mutation(Expression,NewExpression).
19
20		% randomly replaces ground integer ast nodes with a matching
21		% integer expression
22
23		% leaves
24		random_int_expr_mutation(Node,Mutation) :-
25		prob_is_ground(Node,Res) , Res = true ,
26		replace_ground_with_expr(Node,Mutation).
27
28		% two argument expressions
29		random_int_expr_mutation(b(Expression,integer,Info),b(NewExpression,integer,Info)) :-
30		Expression =.. [Type,Expr1,Expr2] ,
31		member(Type,[add,minus,multiplication,div,modulo,power_of]) ,
32		% random choice heuristic for argument
33		random(0,3,R) ,
34		% if expression is ground replace its value by an arithmetic expression
35		random_int_expr_mutation_aux(R,Expr1,Expr2,NewExpr1,NewExpr2) ,
36		NewExpression =.. [Type,NewExpr1,NewExpr2].
37		random_int_expr_mutation(b(Expression,integer,Info),b(NewExpression,integer,Info)) :-
38		Expression =.. [Type,Expr1,Expr2] ,
39		random_int_expr_mutation(Expr1,NewExpr1) ,
40		random_int_expr_mutation(Expr2,NewExpr2) ,
41		NewExpression =.. [Type,NewExpr1,NewExpr2].
42
43		% one argument expressions
44		random_int_expr_mutation(b(Expression,integer,Info),b(NewExpression,integer,Info)) :-
45		Expression =.. [Type,_] ,
46		\+member(Type,[max,min]) ,
47		(prob_is_ground(b(Expression,integer,Info),true)
48		-> replace_ground_with_expr(b(Expression,integer,Info),NewExpr)
49		; random_int_expr_mutation(b(Expression,integer,Info),NewExpr)) ,
50		NewExpression =.. [Type,NewExpr].
51		% no mutation for max_int, min_int, max, min or identifier
52		random_int_expr_mutation(Expression,Expression).
53
54		% either mutate only one argument or both
55		random_int_expr_mutation_aux(0,Expr1,Expr2,NewExpr1,Expr2) :-
56		random_int_expr_mutation_aux2(Expr1,NewExpr1).
57		random_int_expr_mutation_aux(1,Expr1,Expr2,Expr1,NewExpr2) :-
58		random_int_expr_mutation_aux2(Expr2,NewExpr2).
59		random_int_expr_mutation_aux(2,Expr1,Expr2,NewExpr1,NewExpr2) :-
60		random_int_expr_mutation_aux2(Expr1,NewExpr1) ,
61		random_int_expr_mutation_aux2(Expr2,NewExpr2).
62		random_int_expr_mutation_aux2(Expr,NewExpr) :-
63		prob_is_ground(Expr,Res) , Res = true , ! ,
64		replace_ground_with_expr(Expr,NewExpr).
65		random_int_expr_mutation_aux2(Expr,NewExpr) :-
66		random_int_expr_mutation(Expr,NewExpr).
67
68		% replace ground value with an integer expression
69		replace_ground_with_expr(b(unary_minus(Integer),integer,[]),NewExpr) :-
70		replace_ground_with_expr(Integer,TempNewExpr) ,
71		NewExpr = b(multiplication(b(unary_minus(b(integer(1),integer,[])),integer,[]),TempNewExpr),integer,[]).
72		replace_ground_with_expr(b(integer(Value),integer,Info),NewExpr) :-
73		find_expr_clpfd(Value,Expr) , ! ,
74		% random choice of further mutation
75		random(0,10,R) ,
76		(R < 3
77		-> NewExpr = b(Expr,integer,Info)
78		; random_int_expr_mutation(b(Expr,integer,Info),NewExpr)).
79
80		% evaluate an expression using clpfd labeling to mutate a specific value
81		find_expr_clpfd(Value,Expr) :-
82		Val1 in -100000..100000 ,
83		Val2 in -100000..100000 ,
84		random_member(Operator,[add,minus,multiplication]) , % power_of, modulo, div
85		find_expr_aux_operator(Operator,Val1,Val2,Value) ,
86		labeling([],[Val1,Val2]) ,
87		Expr =.. [Operator,b(integer(Val1),integer,[]),b(integer(Val2),integer,[])].
88		% if labeling failed try another expression
89		find_expr_clpfd(Value,Expr) :-
90		find_expr_clpfd(Value,Expr).
91
92		find_expr_aux_operator(add,Val1,Val2,Value) :-
93		Val1 + Val2 #= Value.
94		find_expr_aux_operator(minus,Val1,Val2,Value) :-
95		Val1 - Val2 #= Value.
96		find_expr_aux_operator(div,Val1,Val2,Value) :-
97		Val2 #\= 0 ,
98		Val1 div Val2 #= Value.
99		find_expr_aux_operator(modulo,Val1,Val2,Value) :-
100		Val1 in 1..100000 ,
101		Val2 in 1..100000 , % no negative numbers
102		Val1 mod Val2 #= Value.
103		find_expr_aux_operator(_,Val1,Val2,Value) :-
104		Val1 * Val2 #= Value.