From dd4f13e7f507ec7fd248e997cda9a85e835a8245 Mon Sep 17 00:00:00 2001
From: Titusz Pan <titusz.pan@gmail.com>
Date: Thu, 7 Dec 2023 12:31:20 +0100
Subject: [PATCH] Improve simhash performance

---
 build.py              |  6 ++----
 iscc_core/simhash.pxd |  1 +
 iscc_core/simhash.py  | 15 ++++++++-------
 3 files changed, 11 insertions(+), 11 deletions(-)
 create mode 100644 iscc_core/simhash.pxd

diff --git a/build.py b/build.py
index 6051570..63c6a33 100644
--- a/build.py
+++ b/build.py
@@ -5,6 +5,7 @@
 The shared library can also be built manually using the command:
 $ cythonize -X language_level=3 -a -i ./iscc_core/cdc.py
 $ cythonize -X language_level=3 -a -i ./iscc_core/minhash.py
+$ cythonize -X language_level=3 -a -i ./iscc_core/simhash.py
 """
 try:
     from Cython.Build import cythonize, build_ext
@@ -43,10 +44,7 @@ def build(setup_kwargs):
             setup_kwargs.update(
                 dict(
                     ext_modules=cythonize(
-                        [
-                            "iscc_core/cdc.py",
-                            "iscc_core/minhash.py",
-                        ]
+                        ["iscc_core/cdc.py", "iscc_core/minhash.py", "iscc_core/simhash.py"]
                     ),
                     cmdclass=dict(build_ext=build_ext_gracefull),
                 )
diff --git a/iscc_core/simhash.pxd b/iscc_core/simhash.pxd
new file mode 100644
index 0000000..0a12c37
--- /dev/null
+++ b/iscc_core/simhash.pxd
@@ -0,0 +1 @@
+cpdef bytes alg_simhash(list[bytes] hash_digests)
diff --git a/iscc_core/simhash.py b/iscc_core/simhash.py
index 89d20cf..32f032d 100644
--- a/iscc_core/simhash.py
+++ b/iscc_core/simhash.py
@@ -1,4 +1,5 @@
 # -*- coding: utf-8 -*-
+from bitarray import bitarray
 
 
 def alg_simhash(hash_digests):
@@ -16,16 +17,16 @@ def alg_simhash(hash_digests):
     vector = [0] * n_bits
 
     for digest in hash_digests:
-        h = int.from_bytes(digest, "big", signed=False)
-
+        h = bitarray()
+        h.frombytes(digest)
         for i in range(n_bits):
-            vector[i] += h & 1
-            h >>= 1
+            vector[i] += h[i]
 
-    minfeatures = len(hash_digests) * 1.0 / 2
+    minfeatures = len(hash_digests) / 2
     shash = 0
 
     for i in range(n_bits):
-        shash |= int(vector[i] >= minfeatures) << i
+        if vector[i] >= minfeatures:
+            shash |= 1 << (n_bits - 1 - i)
 
-    return shash.to_bytes(n_bytes, "big", signed=False)
+    return shash.to_bytes(n_bytes, "big")