Make surjection pruning less orientation-dependent and fix short tail check

src/surjector.cpp

@@ -4038,8 +4038,8 @@ using namespace std;
             for (int i = 0; i < path_chunks.size(); ++i) {
                 auto& chunk = path_chunks[i];
                 // Mark anchors that are themselves suspicious as not to be kept.
-                if (chunk.first.first == path_chunks.front().first.first && chunk.first.second == path_chunks.back().first.second
-                    && (anchor_lengths[i] <= max_tail_anchor_prune || chunk.first.second - chunk.first.first <= max_tail_anchor_prune)) {
+                if ((chunk.first.first == path_chunks.front().first.first || chunk.first.second == path_chunks.back().first.second) // Is at either tail
+                    && (anchor_lengths[i] <= max_tail_anchor_prune || chunk.first.second - chunk.first.first <= max_tail_anchor_prune)) { // And is too short
 #ifdef debug_anchored_surject
                     cerr << "anchor " << i << " (read interval " << (chunk.first.first - sequence.begin()) << " : " << (chunk.first.second - sequence.begin()) << ") pruned for being a short tail" << endl;
 #endif
@@ -4050,19 +4050,49 @@ using namespace std;
                 if ((anchor_lengths[i] <= max_low_complexity_anchor_prune || chunk.first.second - chunk.first.first <= max_low_complexity_anchor_prune)) {
                     SeqComplexity<6> chunk_complexity(chunk.first.first, chunk.first.second);
                     if (chunk.first.second - chunk.first.first < pad_suspicious_anchors_to_length) {
-                        auto read_context_begin = max(sequence.begin(), chunk.first.first - (pad_suspicious_anchors_to_length - (chunk.first.second - chunk.first.first)) / 2);
-                        auto read_context_end = min(sequence.end(), read_context_begin + pad_suspicious_anchors_to_length);
-                        if (read_context_end == sequence.end()) {
-                            // try to ensure enough bases if we're near the end of the read
-                            read_context_begin = max(sequence.begin(), read_context_end - pad_suspicious_anchors_to_length);
+                        // We need to fetch out a sequence at least pad_suspicious_anchors_to_length bp long (unless the whole sequence is shorter) and analyze that.
+
+                        // There's no way to symmetrically (and thus
+                        // independently of orientation) get an even-length
+                        // window around an odd-length window, or visa versa.
+                        // So express everything as per-side padding, and round it up.
+                        size_t chunk_length = chunk.first.second - chunk.first.first;
+                        size_t padding_per_side = (pad_suspicious_anchors_to_length - chunk_length + 1) / 2;
+
+                        // Pad separately on each side to avoid read bounds
+                        size_t left_padding = padding_per_side;
+                        size_t right_padding = padding_per_side;
+
+                        // Shift the padded window right if we hit the start
+                        size_t start_offset = chunk.first.first - sequence.begin();
+                        if (start_offset < left_padding) {
+                            right_padding += (left_padding - start_offset);
+                            left_padding = start_offset;
+                        }
+
+                        // Shift the padded window left if we hit the end
+                        size_t remaining_until_end = sequence.end() - chunk.first.second;
+                        if (remaining_until_end < right_padding) {
+                            left_padding += (right_padding - remaining_until_end);
+                            right_padding = remaining_until_end;
                         }
+
+                        // If we hit the start again, clip since the whole window doesn't fit.
+                        left_padding = min(left_padding, start_offset);
+
+                        // TODO: Is there a more closed-form way to budge the padding?
+
+                        // Now expand the iterator range without ever constructing pre-begin iterators
+                        auto read_context_begin = chunk.first.first - left_padding;
+                        auto read_context_end = chunk.first.second + right_padding;
+
                         SeqComplexity<6> context_complexity(read_context_begin, read_context_end);
                         // TODO: repetitive
                         for (int order = 1, max_order = 6; order <= max_order; ++order) {
                             //cerr << "padded anchor " << i << " (read[" << (chunk.first.first - sequence.begin()) << ":" << (chunk.first.second - sequence.begin()) << "]), seq " << string(read_context_begin, read_context_end) << ", order " << order << " with p-value " << context_complexity.p_value(order) << ", repetitive fraction " << chunk_complexity.repetitiveness(order) << endl;
                             if (context_complexity.p_value(order) < low_complexity_p_value) {
 #ifdef debug_anchored_surject
-                                cerr << "anchor " << i << " (read[" << (chunk.first.first - sequence.begin()) << ":" << (chunk.first.second - sequence.begin()) << "]) pruned being for having context with low complexity at order " << order << ", p-value " << context_complexity.p_value(order) << " and anchor repetitive fraction " << chunk_complexity.repetitiveness(order) << endl;
+                                cerr << "anchor " << i << " (read[" << (chunk.first.first - sequence.begin()) << ":" << (chunk.first.second - sequence.begin()) << "]) pruned for having context with low complexity at order " << order << ", p-value " << context_complexity.p_value(order) << " and anchor repetitive fraction " << chunk_complexity.repetitiveness(order) << endl;
 #endif
                                 // the sequences is repetitive at this order
                                 keep[i] = false;

src/surjector.hpp

@@ -132,6 +132,10 @@ using namespace std;
         double low_complexity_p_value = .0075;
         int64_t max_low_complexity_anchor_prune = 40;
         int64_t max_low_complexity_anchor_trim = 65;
+        /// When examining anchors for suspiciousness, try and make them at
+        /// least this long. To ensure orientation symmetry, we will make
+        /// anchors with the oppsite parity (even if this is odd, or odd if
+        /// this is even) 1bp longer.
         int64_t pad_suspicious_anchors_to_length = 12;
 
         // A function for computing band padding

test/surject/opposite_strands.gaf

@@ -0,0 +1,2 @@
+forward	35	0	35	+	>56629809>56629810>56629811>56629814>56629815>56629819>56629820>56629822	132	97	132	35	35	0	cs:Z::35
+reverse	35	0	35	+	<56629822<56629820<56629819<56629815<56629814<56629811<56629810<56629809	132	0	35	35	35	0	cs:Z::35

test/surject/opposite_strands.gfa

@@ -0,0 +1,43 @@
+H	VN:Z:1.1	RS:Z:GRCh38 CHM13
+S	56629807	G
+S	56629808	T
+S	56629809	TTTCTGATTATAAATATTGCACATGTATTGATTACATAAATCCATATACTATAAAACTGATATTTAAGAGAATAAAAGTCCCAACCTCAGAATTAACTACTG
+S	56629810	C
+S	56629811	A
+S	56629812	A
+S	56629813	C
+S	56629814	CCCCC
+S	56629815	C
+S	56629816	G
+S	56629817	T
+S	56629818	T
+S	56629819	T
+S	56629820	TTTTTTTTTTT
+S	56629821	T
+S	56629822	GATGGAGTCT
+S	56629823	C
+S	56629824	G
+W	CHM13	0	chr8	81560724	81560860	>56629807>56629809>56629810>56629813>56629814>56629817>56629818>56629819>56629820>56629821>56629822>56629824
+W	GRCh38	0	chr8	35183939	35184073	>56629807>56629809>56629810>56629811>56629814>56629815>56629819>56629820>56629822>56629823
+L	56629807	+	56629809	+	0M
+L	56629808	+	56629809	+	0M
+L	56629809	+	56629812	-	0M
+L	56629809	+	56629810	+	0M
+L	56629810	+	56629813	+	0M
+L	56629810	+	56629811	+	0M
+L	56629811	+	56629814	+	0M
+L	56629812	-	56629813	+	0M
+L	56629813	+	56629814	+	0M
+L	56629814	+	56629817	+	0M
+L	56629814	+	56629815	+	0M
+L	56629815	+	56629819	+	0M
+L	56629815	+	56629816	-	0M
+L	56629816	-	56629819	+	0M
+L	56629817	+	56629818	+	0M
+L	56629818	+	56629819	+	0M
+L	56629819	+	56629820	+	0M
+L	56629820	+	56629822	+	0M
+L	56629820	+	56629821	+	0M
+L	56629821	+	56629822	+	0M
+L	56629822	+	56629824	+	0M
+L	56629822	+	56629823	+	0M

test/t/15_vg_surject.t

@@ -6,7 +6,7 @@ BASH_TAP_ROOT=../deps/bash-tap
 PATH=../bin:$PATH # for vg
 
 
-plan tests 47
+plan tests 48
 
 vg construct -r small/x.fa >j.vg
 vg index -x j.xg j.vg
@@ -198,3 +198,5 @@ is "$(vg surject -x x.xg -M -m -s -i -t 1 mapped.gamp | grep -v '@' | wc -l)" 80
 
 rm x.vg x.pathdup.vg x.xg x.gcsa x.gcsa.lcp x.gam mapped.gam mapped.gamp
 
+is "$(vg surject -p CHM13#0#chr8 -x surject/opposite_strands.gfa --prune-low-cplx --sam-output --gaf-input surject/opposite_strands.gaf | grep -v "^@" | cut -f3-12 | sort | uniq | wc -l)" "1" "vg surject low compelxity pruning gets the same alignment regardless of read orientation"
+