unknown Initial ITS Start location: [1] Program variables: x y 0: [1] -> [2] : (x >= 0 /\ y >= 0), cost: 1 8: [1] -> [8] : (x < 0 \/ y < 0), cost: 1 1: [2] -> [3] : y'=-1+y, T, cost: 1 2: [3] -> [5] : y < 0, cost: 1 6: [3] -> [4] : y >= 0, cost: 1 7: [4] -> [1] : T, cost: 1 3: [5] -> [6] : x'=-1+x, T, cost: 1 4: [6] -> [7] : y'=nondet, T, cost: 1 5: [7] -> [4] : T, cost: 1 Chained Linear Paths Start location: [1] Program variables: x y 8: [1] -> [8] : (x < 0 \/ y < 0), cost: 1 9: [1] -> [3] : y'=-1+y, (x >= 0 /\ y >= 0), cost: 1 6: [3] -> [4] : y >= 0, cost: 1 12: [3] -> [4] : x'=-1+x, y'=nondet, y < 0, cost: 1 7: [4] -> [1] : T, cost: 1 Eliminating location [2] by chaining: Applied chaining First rule: [1] -> [2] : (x >= 0 /\ y >= 0), cost: 1 Second rule: [2] -> [3] : y'=-1+y, T, cost: 1 New rule: [1] -> [3] : y'=-1+y, (x >= 0 /\ y >= 0), cost: 1 Applied deletion Removed the following rules: 0 1 Eliminating location [5] by chaining: Applied chaining First rule: [3] -> [5] : y < 0, cost: 1 Second rule: [5] -> [6] : x'=-1+x, T, cost: 1 New rule: [3] -> [6] : x'=-1+x, y < 0, cost: 1 Applied deletion Removed the following rules: 2 3 Eliminating location [6] by chaining: Applied chaining First rule: [3] -> [6] : x'=-1+x, y < 0, cost: 1 Second rule: [6] -> [7] : y'=nondet, T, cost: 1 New rule: [3] -> [7] : x'=-1+x, y'=nondet, y < 0, cost: 1 Applied deletion Removed the following rules: 4 10 Eliminating location [7] by chaining: Applied chaining First rule: [3] -> [7] : x'=-1+x, y'=nondet, y < 0, cost: 1 Second rule: [7] -> [4] : T, cost: 1 New rule: [3] -> [4] : x'=-1+x, y'=nondet, y < 0, cost: 1 Applied deletion Removed the following rules: 5 11 Step with 8 Trace 8[(x < 0)] Blocked [{}, {}] Backtrack Trace Blocked [{8[x < 0]}] Step with 8 Trace 8[(y < 0)] Blocked [{8[x < 0]}, {}] Backtrack Trace Blocked [{8[(x < 0 /\ y < 0)]}] Step with 9 Trace 9[(x >= 0 /\ y >= 0)] Blocked [{8[T]}, {}] Step with 6 Trace 9[(x >= 0 /\ y >= 0)], 6[(y >= 0)] Blocked [{8[T]}, {}, {}] Step with 7 Trace 9[(x >= 0 /\ y >= 0)], 6[(y >= 0)], 7[T] Blocked [{8[T]}, {}, {}, {}] Accelerate Start location: [1] Program variables: x y 8: [1] -> [8] : (x < 0 \/ y < 0), cost: 1 9: [1] -> [3] : y'=-1+y, (x >= 0 /\ y >= 0), cost: 1 13: [1] -> [1] : y'=-n+y, (1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0), cost: 1 6: [3] -> [4] : y >= 0, cost: 1 12: [3] -> [4] : x'=-1+x, y'=nondet, y < 0, cost: 1 7: [4] -> [1] : T, cost: 1 Loop Acceleration Original rule: [1] -> [1] : y'=-1+y, (x >= 0 /\ -1+y >= 0 /\ y >= 0), cost: 1 New rule: [1] -> [1] : y'=-n+y, (1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0), cost: 1 x >= 0 [0]: monotonic increase yields x >= 0 -1+y >= 0 [0]: montonic decrease yields -n+y >= 0 -1+y >= 0 [1]: eventual increase yields (1 <= 0 /\ -1+y >= 0) y >= 0 [0]: montonic decrease yields 1-n+y >= 0 y >= 0 [1]: eventual increase yields (1 <= 0 /\ y >= 0) Replacement map: {x >= 0 -> x >= 0, -1+y >= 0 -> -n+y >= 0, y >= 0 -> 1-n+y >= 0} Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)] Blocked [{8[T]}, {13[T]}] Step with 9 Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)] Blocked [{8[T]}, {8[T], 13[T]}, {}] Step with 6 Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)], 6[(y >= 0)] Blocked [{8[T]}, {8[T], 13[T]}, {}, {}] Step with 7 Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)], 6[(y >= 0)], 7[T] Blocked [{8[T]}, {8[T], 13[T]}, {}, {}, {}] Covered Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)], 6[(y >= 0)] Blocked [{8[T]}, {8[T], 13[T]}, {}, {7[T]}] Backtrack Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)] Blocked [{8[T]}, {8[T], 13[T]}, {6[T]}] Step with 12 Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)], 12[(y < 0)] Blocked [{8[T]}, {8[T], 13[T]}, {6[T]}, {}] Step with 7 Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)], 12[(y < 0)], 7[T] Blocked [{8[T]}, {8[T], 13[T]}, {6[T]}, {}, {}] Accelerate Start location: [1] Program variables: x y 8: [1] -> [8] : (x < 0 \/ y < 0), cost: 1 9: [1] -> [3] : y'=-1+y, (x >= 0 /\ y >= 0), cost: 1 13: [1] -> [1] : y'=-n+y, (1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0), cost: 1 14: [1] -> [1] : x'=x-n2, y'=0, (1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0), cost: 1 6: [3] -> [4] : y >= 0, cost: 1 12: [3] -> [4] : x'=-1+x, y'=nondet, y < 0, cost: 1 7: [4] -> [1] : T, cost: 1 Loop Acceleration Original rule: [1] -> [1] : x'=-1+x, y'=nondet1, (x >= 0 /\ -1+y < 0 /\ y >= 0), cost: 1 New rule: [1] -> [1] : x'=x-n2, y'=nondet1, (1+x-n2 >= 0 /\ 1-nondet1 > 0 /\ nondet1 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0), cost: 1 x >= 0 [0]: montonic decrease yields 1+x-n2 >= 0 x >= 0 [1]: eventual increase yields (1 <= 0 /\ x >= 0) 1-y > 0 [0]: eventual decrease yields (1-nondet1 > 0 /\ 1-y > 0) 1-y > 0 [1]: eventual increase yields (nondet1-y <= 0 /\ 1-y > 0) y >= 0 [0]: eventual decrease yields (nondet1 >= 0 /\ y >= 0) y >= 0 [1]: eventual increase yields (y >= 0 /\ -nondet1+y <= 0) Replacement map: {x >= 0 -> 1+x-n2 >= 0, 1-y > 0 -> (1-nondet1 > 0 /\ 1-y > 0), y >= 0 -> (nondet1 >= 0 /\ y >= 0)} made implied equalities explicit Original rule: [1] -> [1] : x'=x-n2, y'=nondet1, (1+x-n2 >= 0 /\ 1-nondet1 > 0 /\ nondet1 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0), cost: 1 New rule: [1] -> [1] : x'=x-n2, y'=nondet1, (1+x-n2 >= 0 /\ 1-nondet1 > 0 /\ nondet1 >= 0 /\ nondet1 == 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0), cost: 1 Propagated Equalities Original rule: [1] -> [1] : x'=x-n2, y'=nondet1, (1+x-n2 >= 0 /\ 1-nondet1 > 0 /\ nondet1 >= 0 /\ nondet1 == 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0), cost: 1 New rule: [1] -> [1] : x'=x-n2, y'=0, (0 >= 0 /\ 0 == 0 /\ 1+x-n2 >= 0 /\ 1 > 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0), cost: 1 propagated equality nondet1 = 0 Simplified Guard Original rule: [1] -> [1] : x'=x-n2, y'=0, (0 >= 0 /\ 0 == 0 /\ 1+x-n2 >= 0 /\ 1 > 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0), cost: 1 New rule: [1] -> [1] : x'=x-n2, y'=0, (1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0), cost: 1 Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)] Blocked [{8[T]}, {8[T], 13[T]}, {14[T]}] Acceleration Failed marked recursive suffix as redundant Step with 8 Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)], 8[(x < 0)] Blocked [{8[T]}, {8[T], 13[T]}, {14[T]}, {}] Backtrack Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)] Blocked [{8[T]}, {8[T], 13[T]}, {8[x < 0], 14[T]}] Step with 9 Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)], 9[(x >= 0 /\ y >= 0)] Blocked [{8[T]}, {8[T], 13[T]}, {8[T], 14[T]}, {}] Step with 12 Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)], 9[(x >= 0 /\ y >= 0)], 12[(y < 0)] Blocked [{8[T]}, {8[T], 13[T]}, {8[T], 14[T]}, {}, {}] Step with 7 Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)], 9[(x >= 0 /\ y >= 0)], 12[(y < 0)], 7[T] Blocked [{8[T]}, {8[T], 13[T]}, {8[T], 14[T]}, {}, {}, {}] Covered Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)], 9[(x >= 0 /\ y >= 0)], 12[(y < 0)] Blocked [{8[T]}, {8[T], 13[T]}, {8[T], 14[T]}, {}, {7[T]}] Backtrack Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)], 9[(x >= 0 /\ y >= 0)] Blocked [{8[T]}, {8[T], 13[T]}, {8[T], 14[T]}, {12[T]}] Backtrack Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)] Blocked [{8[T]}, {8[T], 13[T]}, {8[T], 9[T], 14[T]}] Backtrack Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)] Blocked [{8[T]}, {8[T], 13[T], 14[T]}] Step with 9 Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)] Blocked [{8[T]}, {8[T], 13[T], 14[T]}, {}] Step with 12 Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)], 12[(y < 0)] Blocked [{8[T]}, {8[T], 13[T], 14[T]}, {}, {}] Step with 7 Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)], 12[(y < 0)], 7[T] Blocked [{8[T]}, {8[T], 13[T], 14[T]}, {}, {}, {}] Covered Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)], 12[(y < 0)] Blocked [{8[T]}, {8[T], 13[T], 14[T]}, {}, {7[T]}] Backtrack Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)] Blocked [{8[T]}, {8[T], 13[T], 14[T]}, {12[T]}] Step with 6 Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)], 6[(y >= 0)] Blocked [{8[T]}, {8[T], 13[T], 14[T]}, {12[T]}, {}] Step with 7 Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)], 6[(y >= 0)], 7[T] Blocked [{8[T]}, {8[T], 13[T], 14[T]}, {12[T]}, {}, {}] Covered Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)], 6[(y >= 0)] Blocked [{8[T]}, {8[T], 13[T], 14[T]}, {12[T]}, {7[T]}] Backtrack Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)], 9[(x >= 0 /\ y >= 0)] Blocked [{8[T]}, {8[T], 13[T], 14[T]}, {6[T], 12[T]}] Backtrack Trace 13[(1-n+y >= 0 /\ -n+y >= 0 /\ -1+n >= 0 /\ x >= 0)] Blocked [{8[T]}, {8[T], 9[T], 13[T], 14[T]}] Backtrack Trace Blocked [{8[T], 13[T]}] Step with 9 Trace 9[(x >= 0 /\ y >= 0)] Blocked [{8[T], 13[T]}, {}] Step with 6 Trace 9[(x >= 0 /\ y >= 0)], 6[(y >= 0)] Blocked [{8[T], 13[T]}, {}, {}] Step with 7 Trace 9[(x >= 0 /\ y >= 0)], 6[(y >= 0)], 7[T] Blocked [{8[T], 13[T]}, {}, {}, {}] Covered Trace 9[(x >= 0 /\ y >= 0)], 6[(y >= 0)] Blocked [{8[T], 13[T]}, {}, {7[T]}] Backtrack Trace 9[(x >= 0 /\ y >= 0)] Blocked [{8[T], 13[T]}, {6[T]}] Step with 12 Trace 9[(x >= 0 /\ y >= 0)], 12[(y < 0)] Blocked [{8[T], 13[T]}, {6[T]}, {}] Step with 7 Trace 9[(x >= 0 /\ y >= 0)], 12[(y < 0)], 7[T] Blocked [{8[T], 13[T]}, {6[T]}, {}, {}] Covered Trace 9[(x >= 0 /\ y >= 0)], 12[(y < 0)] Blocked [{8[T], 13[T]}, {6[T]}, {7[T]}] Backtrack Trace 9[(x >= 0 /\ y >= 0)] Blocked [{8[T], 13[T]}, {6[T], 12[T]}] Backtrack Trace Blocked [{8[T], 9[T], 13[T]}] Step with 14 Trace 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)] Blocked [{8[T], 9[T], 13[T]}, {14[T]}] Step with 8 Trace 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)], 8[(x < 0)] Blocked [{8[T], 9[T], 13[T]}, {14[T]}, {}] Backtrack Trace 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)] Blocked [{8[T], 9[T], 13[T]}, {8[x < 0], 14[T]}] Step with 9 Trace 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)], 9[(x >= 0 /\ y >= 0)] Blocked [{8[T], 9[T], 13[T]}, {8[T], 14[T]}, {}] Step with 12 Trace 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)], 9[(x >= 0 /\ y >= 0)], 12[(y < 0)] Blocked [{8[T], 9[T], 13[T]}, {8[T], 14[T]}, {}, {}] Step with 7 Trace 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)], 9[(x >= 0 /\ y >= 0)], 12[(y < 0)], 7[T] Blocked [{8[T], 9[T], 13[T]}, {8[T], 14[T]}, {}, {}, {}] Covered Trace 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)], 9[(x >= 0 /\ y >= 0)], 12[(y < 0)] Blocked [{8[T], 9[T], 13[T]}, {8[T], 14[T]}, {}, {7[T]}] Backtrack Trace 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)], 9[(x >= 0 /\ y >= 0)] Blocked [{8[T], 9[T], 13[T]}, {8[T], 14[T]}, {12[T]}] Backtrack Trace 14[(1+x-n2 >= 0 /\ -1+n2 >= 0 /\ 1-y > 0 /\ y >= 0 /\ y == 0)] Blocked [{8[T], 9[T], 13[T]}, {8[T], 9[T], 14[T]}] Backtrack Trace Blocked [{8[T], 9[T], 13[T], 14[T]}] Accept unknown Build SHA: a05f16bf13df659c382799650051f91bf6828c7b