Contig stitcher: improve concordance calculations

Also add more tests for it.

micall/core/contig_stitcher.py

@@ -384,11 +384,29 @@ def slide(start, end):
     return result
 
 
+def disambiguate_concordance(concordance: List[float]) -> List[Tuple[float, int]]:
+    def slide(concordance):
+        count = 0
+        for i, (prev, current, next) in enumerate(sliding_window(concordance)):
+            if current == prev:
+                count += 1
+                yield count
+            else:
+                yield 0
+
+    forward = list(slide(concordance))
+    reverse = list(reversed(list(slide(reversed(concordance)))))
+    for i, (x, f, r) in enumerate(zip(concordance, forward, reverse)):
+        local_rank = f * r
+        global_rank = i if i < len(concordance) / 2 else len(concordance) - i - 1
+        yield (x, local_rank, global_rank)
+
+
 def concordance_to_cut_points(left_overlap, right_overlap, aligned_left, aligned_right, concordance):
     """ Determine optimal cut points for stitching based on sequence concordance in the overlap region. """
 
-    valuator = lambda i: (concordance[i], i if i < len(concordance) / 2 else len(concordance) - i - 1)
-    sorted_concordance_indexes = sorted(range(len(concordance)), key=valuator)
+    concordance_d = list(disambiguate_concordance(concordance))
+    sorted_concordance_indexes = sorted(range(len(concordance)), key=lambda i: concordance_d[i])
     remove_dashes = lambda s: ''.join(c for c in s if c != '-')
 
     for max_concordance_index in reversed(sorted_concordance_indexes):

micall/tests/test_contig_stitcher.py

@@ -4,7 +4,7 @@
 import os
 import pytest
 
-from micall.core.contig_stitcher import split_contigs_with_gaps, stitch_contigs, GenotypedContig, merge_intervals, find_covered_contig, stitch_consensus, calculate_concordance, align_all_to_reference, main, AlignedContig
+from micall.core.contig_stitcher import split_contigs_with_gaps, stitch_contigs, GenotypedContig, merge_intervals, find_covered_contig, stitch_consensus, calculate_concordance, align_all_to_reference, main, AlignedContig, disambiguate_concordance
 from micall.core.plot_contigs import plot_stitcher_coverage
 from micall.tests.utils import MockAligner, fixed_random_seed
 from micall.utils.structured_logger import add_structured_handler
@@ -974,6 +974,42 @@ def generate_random_string_pair(length):
     right = ''.join(random.choice('ACGT') for _ in range(length))
     return left, right
 
+
+@pytest.mark.parametrize(
+    'left, right, expected',
+    [("aaaaa", "aaaaa", [0.1] * 5),
+     ("abcdd", "abcdd", [0.1] * 5),
+     ("aaaaaaaa", "baaaaaab", [0.1, 0.12, 0.12, 0.12, 0.12, 0.12, 0.12, 0.1]),
+     ("aaaaaaaa", "aaaaaaab", [0.13, 0.13, 0.13, 0.13, 0.13, 0.13, 0.13, 0.12]),
+     ("aaaaaaaa", "aaaaaaab", [0.13, 0.13, 0.13, 0.13, 0.13, 0.13, 0.13, 0.12]),
+     ("aaaaaaaa", "aaaaabbb", [0.1, 0.1, 0.1, 0.1, 0.1, 0.08, 0.08, 0.08]),
+     ("aaaaaaaa", "aaabbaaa", [0.12, 0.12, 0.12, 0.1, 0.1, 0.12, 0.12, 0.12]),
+     ("aaaaa", "bbbbb", [0] * 5),
+     ]
+)
+def test_concordance_simple(left, right, expected):
+    result = [round(x, 2) for x in calculate_concordance(left, right)]
+    assert result == expected
+
+
+@pytest.mark.parametrize(
+    'left, right, expected',
+    [("a" * 128, "a" * 128, 64),
+     ("a" * 128, "a" * 64 + "b" * 64, 32),
+     ("a" * 128, "a" * 64 + "ba" * 32, 32),
+     ("a" * 128, "a" * 54 + "b" * 20 + "a" * 54, 28), # two peaks
+     ("a" * 128, "a" * 63 + "b" * 2 + "a" * 63, 32), # two peaks
+     ("a" * 1280, "b" * 640 + "a" * 640, 640 + 30), # the window is too small to account for all of the context
+     ]
+)
+def test_concordance_simple_index(left, right, expected):
+    concordance = calculate_concordance(left, right)
+    concordance_d = list(disambiguate_concordance(concordance))
+    index = max(range(len(concordance)), key=lambda i: concordance_d[i])
+    if abs(index - expected) > 3:
+        assert index == expected
+
+
 def generate_test_cases(num_cases):
     with fixed_random_seed(42):
         length = random.randint(1, 80)