Break out mpmap band padding algorithm

src/algorithms/pad_band.cpp

@@ -0,0 +1,43 @@
+/**
+ * \file pad_band.cpp
+ * 
+ * Defines implementation for band padding functions for banded global alignment.
+ */
+
+#include "pad_band.hpp"
+
+namespace vg {
+namespace algorithms {
+
+std::function<size_t(const Alignment&, const HandleGraph&)> pad_band_random_walk(double band_padding_multiplier, size_t band_padding_memo_size) {
+
+    // We're goign to capture this vector by value into the closure
+    std::vector<size_t> band_padding_memo;
+
+    // Fill it in to initialize
+    band_padding_memo.resize(band_padding_memo_size);
+    for (size_t i = 0; i < band_padding_memo.size(); i++) {
+        band_padding_memo[i] = size_t(band_padding_multiplier * sqrt(i)) + 1;
+    }
+
+    function<size_t(const Alignment&, const HandleGraph&)> choose_band_padding = [band_padding_multiplier, band_padding_memo](const Alignment& seq, const HandleGraph& graph) {
+        size_t read_length = seq.sequence().size();
+        return read_length < band_padding_memo.size() ? band_padding_memo.at(read_length)
+                                                      : size_t(band_padding_multiplier * sqrt(read_length)) + 1;
+    };
+
+    // And return the closure which now owns the memo table.
+    return choose_band_padding;
+}
+
+std::function<size_t(const Alignment&, const HandleGraph&)> pad_band_constant(size_t band_padding) {
+    // don't dynamically choose band padding, shim constant value into a function type
+    function<size_t(const Alignment&,const HandleGraph&)> constant_padding = [band_padding](const Alignment& seq, const HandleGraph& graph) {
+        return band_padding;
+    };
+
+    return constant_padding;
+}
+
+}
+}

src/algorithms/pad_band.hpp

@@ -0,0 +1,28 @@
+#ifndef VG_ALGORITHMS_PAD_BAND_HPP_INCLUDED
+#define VG_ALGORITHMS_PAD_BAND_HPP_INCLUDED
+
+/**
+ * \file pad_band.hpp
+ *
+ * Defines algorithm for computing band padding for banded alignment.
+ */
+
+#include "../handle.hpp"
+#include <vg/vg.pb.h>
+
+namespace vg {
+namespace algorithms {
+
+using namespace std;
+
+/// Get a band padding function that uses the expected distance of a random
+/// walk, memoized out to the given length.
+std::function<size_t(const Alignment&, const HandleGraph&)> pad_band_random_walk(double band_padding_multiplier = 1.0, size_t band_padding_memo_size = 2000);
+
+/// Get a band padding function that uses a constant value.
+std::function<size_t(const Alignment&, const HandleGraph&)> pad_band_constant(size_t band_padding);
+
+}
+}
+
+#endif

src/multipath_alignment_graph.cpp

@@ -9,6 +9,7 @@
 
 #include "algorithms/extract_connecting_graph.hpp"
 #include "algorithms/extract_extending_graph.hpp"
+#include "algorithms/pad_band.hpp"
 
 //#define debug_multipath_alignment
 //#define debug_decompose_algorithm
@@ -4230,10 +4231,6 @@ void MultipathAlignmentGraph::align(const Alignment& alignment, const HandleGrap
                                     SnarlDistanceIndex* dist_index, const function<pair<id_t, bool>(id_t)>* project,
                                     bool allow_negative_scores, unordered_map<handle_t, bool>* left_align_strand) {
 
-        // don't dynamically choose band padding, shim constant value into a function type
-        function<size_t(const Alignment&,const HandleGraph&)> constant_padding = [&](const Alignment& seq, const HandleGraph& graph) {
-            return band_padding;
-        };
         align(alignment,
               align_graph,
               aligner,
@@ -4244,7 +4241,7 @@ void MultipathAlignmentGraph::align(const Alignment& alignment, const HandleGrap
               pessimistic_tail_gap_multiplier,
               simplify_topologies,
               unmergeable_len,
-              constant_padding,
+              algorithms::pad_band_constant(band_padding),
               multipath_aln_out,
               cutting_snarls,
               dist_index,
@@ -5183,7 +5180,7 @@ void MultipathAlignmentGraph::align(const Alignment& alignment, const HandleGrap
     void MultipathAlignmentGraph::align(const Alignment& alignment, const HandleGraph& align_graph, const GSSWAligner* aligner,
                                         bool score_anchors_as_matches, size_t max_alt_alns, bool dynamic_alt_alns, size_t max_gap,
                                         double pessimistic_tail_gap_multiplier, bool simplify_topologies, size_t unmergeable_len,
-                                        function<size_t(const Alignment&,const HandleGraph&)> band_padding_function,
+                                        const function<size_t(const Alignment&,const HandleGraph&)>& band_padding_function,
                                         multipath_alignment_t& multipath_aln_out, SnarlManager* cutting_snarls,
                                         SnarlDistanceIndex* dist_index, const function<pair<id_t, bool>(id_t)>* project,
                                         bool allow_negative_scores, unordered_map<handle_t, bool>* left_align_strand) {

src/multipath_alignment_graph.hpp

@@ -213,7 +213,7 @@ namespace vg {
         /// with topologically_order_subpaths() before trying to run DP on it.
         void align(const Alignment& alignment, const HandleGraph& align_graph, const GSSWAligner* aligner, bool score_anchors_as_matches,
                    size_t max_alt_alns, bool dynamic_alt_alns, size_t max_gap, double pessimistic_tail_gap_multiplier, bool simplify_topologies,
-                   size_t unmergeable_len, function<size_t(const Alignment&,const HandleGraph&)> band_padding_function,
+                   size_t unmergeable_len, const function<size_t(const Alignment&,const HandleGraph&)>& band_padding_function,
                    multipath_alignment_t& multipath_aln_out, SnarlManager* cutting_snarls = nullptr, SnarlDistanceIndex* dist_index = nullptr,
                    const function<pair<id_t, bool>(id_t)>* project = nullptr, bool allow_negative_scores = false,
                    unordered_map<handle_t, bool>* left_align_strand = nullptr);

src/multipath_mapper.cpp

@@ -45,6 +45,7 @@
 #include "algorithms/jump_along_path.hpp"
 #include "algorithms/ref_path_distance.hpp"
 #include "algorithms/component.hpp"
+#include "algorithms/pad_band.hpp"
 
 namespace vg {
 
@@ -63,7 +64,8 @@ namespace vg {
         snarl_manager(snarl_manager),
         distance_index(distance_index),
         path_component_index(distance_index ? nullptr : new PathComponentIndex(graph)),
-        splice_stats(*get_regular_aligner())
+        splice_stats(*get_regular_aligner()),
+        choose_band_padding(algorithms::pad_band_random_walk(1.0, 0))
     {
         set_max_merge_supression_length();
     }
@@ -895,15 +897,6 @@ namespace vg {
             }
         }
     }
-
-    void MultipathMapper::init_band_padding_memo() {
-        band_padding_memo.clear();
-        band_padding_memo.resize(band_padding_memo_size);
-
-        for (size_t i = 0; i < band_padding_memo.size(); i++) {
-            band_padding_memo[i] = size_t(band_padding_multiplier * sqrt(i)) + 1;
-        }
-    }
 
     void MultipathMapper::set_alignment_scores(const int8_t* score_matrix, int8_t gap_open, int8_t gap_extend,
                                                int8_t full_length_bonus) {
@@ -6248,12 +6241,6 @@ namespace vg {
             }
 #endif
 
-            function<size_t(const Alignment&, const HandleGraph&)> choose_band_padding = [&](const Alignment& seq, const HandleGraph& graph) {
-                size_t read_length = seq.sequence().size();
-                return read_length < band_padding_memo.size() ? band_padding_memo.at(read_length)
-                                                              : size_t(band_padding_multiplier * sqrt(read_length)) + 1;
-            };
-
             // do the connecting alignments and fill out the multipath_alignment_t object
             multi_aln_graph.align(alignment, *align_dag, aligner, true, num_alt_alns, dynamic_max_alt_alns, max_alignment_gap,
                                   use_pessimistic_tail_alignment ? pessimistic_gap_multiplier : 0.0, simplify_topologies,
@@ -6305,12 +6292,6 @@ namespace vg {
         multi_aln_graph.topological_sort(topological_order);
         multi_aln_graph.remove_transitive_edges(topological_order);
 
-        function<size_t(const Alignment&, const HandleGraph&)> choose_band_padding = [&](const Alignment& seq, const HandleGraph& graph) {
-            size_t read_length = seq.sequence().end() - seq.sequence().begin();
-            return read_length < band_padding_memo.size() ? band_padding_memo.at(read_length)
-                                                          : size_t(band_padding_multiplier * sqrt(read_length)) + 1;
-        };
-
         // do the connecting alignments and fill out the multipath_alignment_t object
         multi_aln_graph.align(alignment, subgraph, aligner, false, num_alt_alns, dynamic_max_alt_alns, max_alignment_gap,
                               use_pessimistic_tail_alignment ? pessimistic_gap_multiplier : 0.0, simplify_topologies,

src/multipath_mapper.hpp

@@ -78,9 +78,6 @@ namespace vg {
         /// Experimental: skeleton code for predicting path distance from minimum distance
         void determine_distance_correlation();
 
-        /// Should be called once after construction, or any time the band padding multiplier is changed
-        void init_band_padding_memo();
-
         using AlignerClient::set_alignment_scores;
 
         /// Set the algner scoring parameters and create the stored aligner instances. The
@@ -115,7 +112,6 @@ namespace vg {
         size_t max_tail_merge_supress_length = 4;
         bool suppress_tail_anchors = false;
         size_t min_tail_anchor_length = 3;
-        double band_padding_multiplier = 1.0;
         bool use_pessimistic_tail_alignment = false;
         double pessimistic_gap_multiplier = 0.0;
         bool restrained_graph_extraction = false;
@@ -136,7 +132,6 @@ namespace vg {
         int max_fanout_base_quality = 20;
         int max_fans_out = 5;
         size_t max_p_value_memo_size = 500;
-        size_t band_padding_memo_size = 2000;
         double max_exponential_rate_intercept = 0.612045;
         double max_exponential_rate_slope = 0.000555181;
         double max_exponential_shape_intercept = 12.136;
@@ -688,8 +683,8 @@ namespace vg {
         static thread_local unordered_map<double, vector<int64_t>> pessimistic_gap_memo;
         static const size_t gap_memo_max_size;
 
-        // a memo for transcendental band padidng function (gets initialized at construction)
-        vector<size_t> band_padding_memo;
+        // A function for computing band padding
+        std::function<size_t(const Alignment&, const HandleGraph&)> choose_band_padding;
 
 #ifdef mpmap_instrument_mem_statistics
     public:

src/subcommand/mpmap_main.cpp

@@ -15,6 +15,7 @@
 
 #include <vg/io/vpkg.hpp>
 #include "../algorithms/component.hpp"
+#include "../algorithms/pad_band.hpp"
 #include "../multipath_mapper.hpp"
 #include "../mem_accelerator.hpp"
 #include "../surjector.hpp"
@@ -1900,8 +1901,7 @@ int main_mpmap(int argc, char** argv) {
     }
     multipath_mapper.adjust_alignments_for_base_quality = qual_adjusted;
     multipath_mapper.strip_bonuses = strip_full_length_bonus;
-    multipath_mapper.band_padding_multiplier = band_padding_multiplier;
-    multipath_mapper.init_band_padding_memo();
+    multipath_mapper.choose_band_padding = algorithms::pad_band_random_walk(band_padding_multiplier);
 
     // set mem finding parameters
     multipath_mapper.hit_max = hit_max;