MutaFix run: sortedcontainers-006

ranker nvidia/NVIDIA-Nemotron-3-Nano-30B-A3B · patcher nvidia/nemotron-3-super-120b-a12b · via Nebius Token Factory

fixedoutcome
35swall time
3model calls
$0.0069API cost
Benchmark ground truth (hidden from the agent)
src/sortedcontainers/sortedlist.py:622 · operator CONST · function src/sortedcontainers/sortedlist.py::SortedList._pos
- child = (pos << 2) + 1   (injected bug)+ child = (pos << 1) + 1   (original)
retriever rank 1 of 20 · ranker position 1 · patched the right function yes · exact restore yes

Trace

reproduce
+2.24s
42 failing test(s) · 42 failed, 257 passed · 2.24s
failing tests and errors
tests/benchmark_splits_fill.py::tests.benchmark_splits_fill
tests/test_coverage_sorteddict.py::test_islice
tests/test_coverage_sortedkeylist_modulo.py::test_getitem
tests/test_coverage_sortedkeylist_modulo.py::test_getitem_slice
tests/test_coverage_sortedkeylist_modulo.py::test_delitem
tests/test_coverage_sortedkeylist_modulo.py::test_delitem_slice
tests/test_coverage_sortedkeylist_modulo.py::test_islice
tests/test_coverage_sortedkeylist_negate.py::test_getitem
tests/test_coverage_sortedkeylist_negate.py::test_getitem_slice
tests/test_coverage_sortedkeylist_negate.py::test_delitem
tests/test_coverage_sortedkeylist_negate.py::test_delitem_slice
tests/test_coverage_sortedlist.py::test_getitem
tests/test_coverage_sortedlist.py::test_getitem_slice
tests/test_coverage_sortedlist.py::test_delitem
tests/test_coverage_sortedlist.py::test_delitem_slice
tests/test_coverage_sortedlist.py::test_islice
tests/test_coverage_sortedset.py::test_init
tests/test_coverage_sortedset.py::test_getitem
tests/test_coverage_sortedset.py::test_getitem_slice
tests/test_coverage_sortedset.py::test_getitem_key
tests/benchmark_splits_fill.py::tests.benchmark_splits_fill
(no message)
tests/test_coverage_sorteddict.py::test_islice
E   assert [] == [0, 1, 2, 3, 4, 5, ...]
E     
E     Right contains 7 more items, first extra item: 0
E     Use -v to get more diff
trace
+3.79s
re-ran 5 test file(s) with the trace plugin: 17 failing and 224 passing tests, 30 library functions ran in a failing test · 1.51s
tests/benchmark_splits_fill.py, tests/test_coverage_sorteddict.py, tests/test_coverage_sortedkeylist_modulo.py, tests/test_coverage_sortedkeylist_negate.py, tests/test_coverage_sortedlist.py
retrieve
+3.79s
129 functions indexed, 0 reachable from tests/benchmark_splits_fill.py::tests.benchmark_splits_fill in the static call graph. Kept 20 candidates, ranked by spectrum score (Ochiai), call graph and BM25 break ties.
candidates in retriever order
  1. src/sortedcontainers/sortedlist.py::SortedList._pos call depth - · Ochiai 0.60 (failing 16, passing 26)
  2. src/sortedcontainers/sortedlist.py::SortedList._build_index call depth - · Ochiai 0.60 (failing 16, passing 26)
  3. src/sortedcontainers/sortedlist.py::SortedList.__delitem__ call depth - · Ochiai 0.54 (failing 7, passing 3)
  4. src/sortedcontainers/sortedlist.py::SortedList.islice call depth - · Ochiai 0.42 (failing 3, passing 0)
  5. src/sortedcontainers/sortedlist.py::SortedList.__getitem__ call depth - · Ochiai 0.39 (failing 9, passing 23)
  6. src/sortedcontainers/sortedlist.py::SortedList._reset call depth - · Ochiai 0.31 (failing 15, passing 121)
  7. src/sortedcontainers/sortedlist.py::SortedKeyList._delete call depth - · Ochiai 0.26 (failing 4, passing 10)
  8. src/sortedcontainers/sortedlist.py::SortedList._islice call depth - · Ochiai 0.24 (failing 3, passing 6)
  9. src/sortedcontainers/sortedlist.py::SortedKeyList.add call depth - · Ochiai 0.23 (failing 4, passing 13)
  10. src/sortedcontainers/sortedlist.py::SortedList.clear call depth - · Ochiai 0.23 (failing 7, passing 46)
  11. src/sortedcontainers/sortedlist.py::SortedKeyList.clear call depth - · Ochiai 0.22 (failing 9, passing 87)
  12. src/sortedcontainers/sortedlist.py::SortedList._delete call depth - · Ochiai 0.20 (failing 3, passing 10)
  13. src/sortedcontainers/sortedlist.py::SortedKeyList.update call depth - · Ochiai 0.20 (failing 9, passing 110)
  14. src/sortedcontainers/sortedlist.py::SortedKeyList.__new__ call depth - · Ochiai 0.20 (failing 9, passing 112)
  15. src/sortedcontainers/sortedlist.py::SortedList.__len__ call depth - · Ochiai 0.20 (failing 6, passing 48)
  16. src/sortedcontainers/sortedlist.py::SortedKeyList.__init__ call depth - · Ochiai 0.19 (failing 9, passing 121)
  17. src/sortedcontainers/sortedlist.py::SortedList.__init__ call depth - · Ochiai 0.19 (failing 8, passing 99)
  18. src/sortedcontainers/sortedlist.py::SortedList.__new__ call depth - · Ochiai 0.18 (failing 8, passing 110)
  19. src/sortedcontainers/sortedlist.py::SortedList.update call depth - · Ochiai 0.17 (failing 7, passing 93)
  20. src/sortedcontainers/sortedlist.py::SortedKeyList._expand call depth - · Ochiai 0.15 (failing 3, passing 19)
rank
+3.79s
spectrum order kept (no model call)
  1. src/sortedcontainers/sortedlist.py::SortedList._pos
  2. src/sortedcontainers/sortedlist.py::SortedList._build_index
  3. src/sortedcontainers/sortedlist.py::SortedList.__delitem__
  4. src/sortedcontainers/sortedlist.py::SortedList.islice
  5. src/sortedcontainers/sortedlist.py::SortedList.__getitem__
read
+4.61s
turn 1 · NVIDIA-Nemotron-3-Nano-30B-A3B · 6252 in / 91 out · 0.82s · $0.00040

read src/sortedcontainers/sortedlist.py::SortedList._pos

The failing tests involve indexing and slicing operations that likely stem from incorrect index calculations in the tree navigation logic of _pos. This method is central to converting flat indices into list/sub-list coordinates, and its current implementation may mishandle negative indices or boundary conditions, leading to off-by-one errors or incorrect sublist selection in edge cases.

patch
+6.81s
turn 2 · NVIDIA-Nemotron-3-Nano-30B-A3B · 7747 in / 336 out · 2.2s · $0.00055

patch on src/sortedcontainers/sortedlist.py::SortedList._pos rejected: patched file does not parse: unindent does not match any outer indentation level (line 588)

The logic for handling negative indices in _pos appears flawed. Specifically, when idx is negative and its absolute value exceeds the length of the last list, the code attempts to adjust idx by adding self._len. However, this adjustment may not correctly map to the intended positive index, especially when dealing with edge cases involving the last list's boundaries. The condition `if (-idx) <= last_len` correctly handles cases where the negative index refers to an element within the last list, but the subsequent steps may not properly convert the remaining negative index into a valid positive index for traversal. The issue likely lies in how the remaining negative index is interpreted after this adjustment, leading to incorrect tree traversal and ultimately wrong (pos, idx) pairs.

the edit it proposed
         if idx < 0:
            last_len = len(self._lists[-1])

            if (-idx) <= last_len:
                return len(self._lists) - 1, last_len + idx

            idx += self._len

            if idx < 0:
                raise IndexError('list index out of range')
        if idx < 0:
            last_len = len(self._lists[-1])

            if (-idx) <= last_len:
                return len(self._lists) - 1, last_len + idx

            idx += self._len

            if idx < 0:
                raise IndexError('list index out of range')
patch
+34.63s
turn 3 · nemotron-3-super-120b-a12b · 8129 in / 3894 out · 25.07s · $0.00594

The child index calculation in the tree traversal was incorrect. The comment states that left-child is at pos*2+1 and right-child at pos*2+2, but the code used (pos << 2) + 1 which equals pos*4+1, skipping levels. Changing to (pos << 1) + 1 fixes the tree descent logic.

--- a/src/sortedcontainers/sortedlist.py+++ b/src/sortedcontainers/sortedlist.py@@ -620,5 +620,5 @@                 pos = child + 1 -            child = (pos << 2) + 1+            child = (pos << 1) + 1          return (pos - self._offset, idx)

tests: all tests pass 299 passed

model reasoning (excerpt)
We need to ensure proper indentation. The original lines have specific indentation. Let's look at the exact lines:

Original snippet from candidate 1:

  588 |         if idx < 0:
  589 |             last_len = len(self._lists[-1])
  590 |
  591 |             if (-idx) <= last_len:
  592 |                 return len(self._lists) - 1, last_len + idx
  593 |
  594 |             idx += self._len
  595 |
  596 |             if idx < 0:
  597 |                 raise IndexError('list index out of range')

Note there are blank lines (with just spaces?) Actually lines 590 and 593 and 595 appear to be empty? They show as blank in the snippet but might contain spaces. We need to preserve indentation exactly.

Our patch attempted to replace from line 588 to line 597 inclusive? Actually we replaced from "if idx < 0:" through the block until the raise line. But we kept the same text, which should be fine, but the error says unindent does not match any outer indentation level at line 588. That suggests that after the patch, the indentation of the line "if idx < 0:" is wrong relative to its context.

Maybe we accidentally changed indentation because we copied the text but the original had 8 spaces? Actually the method body is indented with 8 spaces (two tabs? but likely 8 spaces). The lines we are replacing start at column 8? Let's check: The method definition line 533 has no leading spaces? Actually the file likely uses 4 spaces per indent. The class is indented, then method. But we don't

Final patch

--- a/src/sortedcontainers/sortedlist.py+++ b/src/sortedcontainers/sortedlist.py@@ -620,5 +620,5 @@                 pos = child + 1 -            child = (pos << 2) + 1+            child = (pos << 1) + 1          return (pos - self._offset, idx)