merge #395 and #615 for fast gather

sourmash/_minhash.pxd

@@ -30,6 +30,7 @@ cdef extern from "kmer_min_hash.hh":
 
         KmerMinHash(unsigned int, unsigned int, bool, uint32_t, HashIntoType)
         void add_hash(HashIntoType) except +ValueError
+        void remove_hash(HashIntoType) except +ValueError
         void add_word(string word) except +ValueError
         void add_sequence(const char *, bool) except +ValueError
         void merge(const KmerMinHash&) except +ValueError
@@ -42,6 +43,7 @@ cdef extern from "kmer_min_hash.hh":
 
         KmerMinAbundance(unsigned int, unsigned int, bool, uint32_t, HashIntoType)
         void add_hash(HashIntoType) except +ValueError
+        void remove_hash(HashIntoType) except +ValueError
         void add_word(string word) except +ValueError
         void add_sequence(const char *, bool) except +ValueError
         void merge(const KmerMinAbundance&) except +ValueError

sourmash/_minhash.pyx

@@ -189,6 +189,11 @@ cdef class MinHash(object):
         for hash in hashes:
             self.add_hash(hash)
 
+    def remove_many(self, hashes):
+        "Remove many hashes at once."
+        for hash in hashes:
+            deref(self._this).remove_hash(hash)
+
     def update(self, other):
         "Update this estimator from all the hashes from the other."
         self.add_many(other.get_mins())

sourmash/kmer_min_hash.hh

@@ -114,6 +114,14 @@ public:
         }
       }
     }
+
+    virtual void remove_hash(const HashIntoType h) {
+        auto pos = std::lower_bound(std::begin(mins), std::end(mins), h);
+        if (pos != mins.cend() and *pos == h) {
+          mins.erase(pos);
+        }
+    }
+
     void add_word(const std::string& word) {
         const HashIntoType hash = _hash_murmur(word, seed);
         add_hash(hash);
@@ -343,6 +351,15 @@ class KmerMinAbundance: public KmerMinHash {
       }
     }
 
+    virtual void remove_hash(const HashIntoType h) {
+        auto pos = std::lower_bound(std::begin(mins), std::end(mins), h);
+        if (pos != mins.cend() and *pos == h) {
+          mins.erase(pos);
+          size_t dist = std::distance(begin(mins), pos);
+          abunds.erase(begin(abunds) + dist);
+        }
+    }
+
     virtual void merge(const KmerMinAbundance& other) {
         check_compatible(other);
 

sourmash/sbtmh.py

@@ -219,15 +219,20 @@ def __init__(self, initial_best_match=0.0):
 
     def search(self, node, query, threshold, results=None):
         score = 0
-
         if not len(query.minhash):
             return 0
 
         if isinstance(node, SigLeaf):
             max_scaled = max(node.data.minhash.scaled, query.minhash.scaled)
 
-            mh1 = node.data.minhash.downsample_scaled(max_scaled)
-            mh2 = query.minhash.downsample_scaled(max_scaled)
+            mh1 = node.data.minhash
+            if mh1.scaled != max_scaled:
+                mh1 = node.data.minhash.downsample_scaled(max_scaled)
+
+            mh2 = query.minhash
+            if mh2.scaled != max_scaled:
+                mh2 = query.minhash.downsample_scaled(max_scaled)
+
             matches = mh1.count_common(mh2)
             score = float(matches) / len(query.minhash)
         else:  # Nodegraph by minhash comparison

sourmash/search.py

@@ -107,9 +107,19 @@ def search_databases(query, databases, threshold, do_containment, best_only,
     return results
 
 
+# define a function to build new query object
+def build_new_query(to_remove, old_query, scaled=None):
+    e = old_query.minhash
+    e.remove_many(to_remove)
+    if scaled:
+        e = e.downsample_scaled(scaled)
+    return SourmashSignature(e)
+
+
 GatherResult = namedtuple('GatherResult',
                           'intersect_bp, f_orig_query, f_match, f_unique_to_query, f_unique_weighted, average_abund, median_abund, std_abund, filename, name, md5, leaf')
 
+
 def gather_databases(query, databases, threshold_bp, ignore_abundance):
     orig_query = query
     orig_mins = orig_query.minhash.get_hashes()
@@ -174,17 +184,8 @@ def find_best(dblist, query, remainder):
         return best_similarity, best_leaf, filename
 
 
-    # define a function to build new signature object from set of mins
-    def build_new_signature(mins, template_sig, scaled=None):
-        e = template_sig.minhash.copy_and_clear()
-        e.add_many(mins)
-        if scaled:
-            e = e.downsample_scaled(scaled)
-        return SourmashSignature(e)
-
     # construct a new query that doesn't have the max_hash attribute set.
-    new_mins = query.minhash.get_hashes()
-    query = build_new_signature(new_mins, orig_query)
+    query = build_new_query([], orig_query)
 
     cmp_scaled = 0
     remainder = set()
@@ -263,8 +264,8 @@ def build_new_signature(mins, template_sig, scaled=None):
                               leaf=best_leaf)
 
         # construct a new query, minus the previous one.
+        query = build_new_query(found_mins, orig_query, cmp_scaled)
         query_mins -= set(found_mins)
-        query = build_new_signature(query_mins, orig_query, cmp_scaled)
 
         weighted_missed = sum((orig_abunds[k] for k in query_mins)) \
              / sum_abunds

tests/test__minhash.py

@@ -1030,3 +1030,41 @@ def test_distance_matrix(track_abundance):
             D1[i][j] = E.similarity(E2, track_abundance)
 
     assert numpy.array_equal(D1, D2)
+
+
+def test_remove_many(track_abundance):
+    a = MinHash(0, 10, track_abundance=track_abundance, max_hash=5000)
+
+    a.add_many(list(range(0, 100, 2)))
+
+    orig_sig = signature.SourmashSignature(a)
+    orig_md5 = orig_sig.md5sum()
+
+    a.remove_many(list(range(0, 100, 3)))
+    new_sig = signature.SourmashSignature(a)
+    new_md5 = new_sig.md5sum()
+
+    assert orig_md5 == "f1cc295157374f5c07cfca5f867188a1"
+    assert new_md5 == "dd93fa319ef57f4a019c59ee1a8c73e2"
+    assert orig_md5 != new_md5
+
+    assert len(a) == 33
+    assert all(c % 6 != 0 for c in a.get_mins())
+
+
+def test_add_many(track_abundance):
+    a = MinHash(0, 10, track_abundance=track_abundance, max_hash=5000)
+    b = MinHash(0, 10, track_abundance=track_abundance, max_hash=5000)
+
+    a.add_many(list(range(0, 100, 2)))
+    a.add_many(list(range(0, 100, 2)))
+
+    assert len(a) == 50
+    assert all(c % 2 == 0 for c in a.get_mins())
+
+    for h in range(0, 100, 2):
+        b.add_hash(h)
+        b.add_hash(h)
+
+    assert len(b) == 50
+    assert a == b