tie break for divmod (#15169)

test/null/test_uop_symbolic.py

@@ -703,6 +703,12 @@ class TestSymbolic(unittest.TestCase):
     self.helper_test_variable((31*b+1)//18, 0, 172, "(((b*13)+1)//18+b)")
     self.helper_test_variable((19*b+3)//7, 0, 271, "(((b*5)+3)//7+(b*2))")
 
+  def test_div_by_factor_tie_break(self):
+    a = Variable("a", 0, 1)
+    b = Variable("b", 0, 1)
+    with Context(CORRECT_DIVMOD_FOLDING=1):
+      self.helper_test_variable((a*2+b*3+2)//6, 0, 1, "((a+b+1)//3)")
+
   def test_div_mod_recombine_large_coeff(self):
     # recombine must work even when coeff > divisor: both mod and div reduce the coeff the same way
     b = Variable("b", 0, 100)

tinygrad/uop/divandmod.py

@@ -70,7 +70,7 @@ def fold_divmod_general(d: UOp, correct_divmod_folding: bool) -> UOp|None:
       for div in {abs(f) for u, f in zip(uops_no_const, factors) if u.op not in (Ops.CONST, Ops.VCONST) and 1 < abs(f) < c and (c%f)==0}:
         if (newxs := fold_divmod_general(x//div, correct_divmod_folding)) is not None and newxs.vmin >= 0:
           results.append((len(newxs.backward_slice), newxs // (c // div)))
-      if results: return min(results)[1]
+      if results: return min(results, key=lambda r: r[0])[1]
 
   # ** Variable Denominator / Fallback Rules **
   # These rules apply to variables OR constants that failed the checks above.