[llvm-branch-commits] [llvm] [Dexter] Add !step node for testing stepping behaviour (PR #203844)

[Orlando Cazalet-Hyams via llvm-branch-commits]

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@@ -156,3 +156,80 @@ def get_variable_metrics(
         "missing_values": ScalarMetric(num_missing_values, improves_asc=False),
     }
     return metrics
+
+
+def lcs_len(a: List[int], b: List[int]) -> int:
+    """Returns the length of the longest common subsequence between a and b."""
+    lcs_table: List[List[int]] = [
+        [0 for _ in range(len(b) + 1)] for _ in range(len(a) + 1)
+    ]
+    for a_idx in range(len(a)):
+        for b_idx in range(len(b)):
+            if a[a_idx] == b[b_idx]:
+                lcs_table[a_idx + 1][b_idx + 1] = 1 + lcs_table[a_idx][b_idx]
+            else:
+                lcs_table[a_idx + 1][b_idx + 1] = max(
+                    lcs_table[a_idx + 1][b_idx], lcs_table[a_idx][b_idx + 1]
+                )
+    return lcs_table[-1][-1]
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OCHyams wrote:

Feels like the kind of thing we'd want some kind of unit test for, but I don't think there's precedent for that in dexter! I didn't dry-run this or anything but code looks fine and impl looks semantically same as some other references 

https://github.com/llvm/llvm-project/pull/203844