Loop Transform using ISL

[Man Xavier]

I'm new to ISL.

I'm trying to Transform AST

for r in range(10)

    for p in range(10)

        S0: A1[0,p] = max(A1[0,p], A0[r,p])

for r in range(10)

    for p in range(10)

        S1: A2[r,p] = A0[r,p] - A1[0,p]

TO AST

for p in range(10)

    for r in range(10)

        S0: A1[0,p] = max(A1[0,p], A0[r,p])

    for r in range(10)

        S1: A2[r,p] = A0[r,p] - A1[0,p]

I use the following code to realize the function:

1. import isl
2. 
   
3. context = isl.set("{ : }")
4. 
   
5. schedule_space = isl.set("{[t0,t1,t2]:}").get_space()
6. precedes = isl.map.lex_lt(schedule_space)
7. 
   
8. # iteration domain
9. domain = isl.union_set(" {S0[i,j] : 0<=i<10 and 0<=j<10; S1[i,j] : 0<=i<10 and 0<=j<10; }")
10. 
    
11. schedule = isl.union_map("{S0[i,j] -> [t0,t1,t2] : t0 = 1 and t1 = i and t2 = j; S1[i,j] -> [t0,t1,t2] : t0 = 2 and  t1 = i and t2 = j}")
12. 
    
13. build = isl.ast_build.from_context(context)
14. ast = build.node_from_schedule_map(schedule.intersect_domain(domain))
15. print(ast.to_C_str())
16. 
    
17. reads = isl.union_map("{S0[i,j] -> A0[a=i,b=j]; S0[i,j] -> A1[a=0,b=j];S1[i,j] -> A1[a=0,b=j];}")
18. reads= reads.intersect_domain(domain)
19. 
    
20. writes = isl.union_map("{S0[i,j] -> A1[a=0,b=j]; S1[i,j] -> A2[a=i,b=j]; S[j] -> A1[0,b=j]}")
21. writes= writes.intersect_domain(domain)
22. 
    
23. raw = writes.apply_range(reads.reverse())
24. raw = raw.apply_domain(schedule).apply_range(schedule)
25. raw = raw.intersect(precedes)
26. raw = raw.apply_domain(schedule.reverse()).apply_range(schedule.reverse())
27. 
    
28. 
    
29. war = reads.apply_range(writes.reverse())
30. war = war.apply_domain(schedule).apply_range(schedule)
31. war = war.intersect(precedes)
32. war = war.apply_domain(schedule.reverse()).apply_range(schedule.reverse())
33. 
    
34. 
    
35. waw = writes.apply_range(writes.reverse())
36. waw = waw.apply_domain(schedule).apply_range(schedule)
37. waw = waw.intersect(precedes)
38. waw = waw.apply_domain(schedule.reverse()).apply_range(schedule.reverse())
39. 
    
40. 
    
41. sc = isl.schedule_constraints.on_domain(domain)
42. dep = war.union(raw).union(waw)
43. 
    
44. sc = sc.set_validity(dep)
45. sc = sc.set_proximity(dep)
46. sched = sc.compute_schedule()
47. build = isl.ast_build.from_context(context)
48. ast = build.node_from(sched)
49. print(ast.to_C_str())

The experimental result is that: WITHOUT line 18 and line 21, I can get the expected AST. 

WITH line 18 and line 21, I can just get the following AST:
  for (int c0 = 0; c0 <= 9; c0 += 1)
    for (int c1 = 0; c1 <= 9; c1 += 1)
      S0(c1, c0);
  for (int c0 = 0; c0 <= 9; c0 += 1)
    for (int c1 = 0; c1 <= 9; c1 += 1)
      S1(c0, c1);

Why does this happen? What is the correct way to realize the transformation?