From bee655358f1c5aedbc30bd9469cab86e607af45f Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Thu, 10 Oct 2024 02:15:39 -0700
Subject: [PATCH 1/3] Update optimized `Delta` codec for `bool`

Previously `bool` just worked with `Delta`. However this was not
actually tested. The optimized version switched to `np.subtract` for
in-place computation, which works for other types. Though `bool` needs
special handling. Fortunately this can be done with `np.not_equal`,
which has the same behavior.

Also include a test for `bool` data to make sure this is handled
correctly going forward.
---
 numcodecs/delta.py            | 5 ++++-
 numcodecs/tests/test_delta.py | 1 +
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/numcodecs/delta.py b/numcodecs/delta.py
index 09a5601e..28a5233e 100644
--- a/numcodecs/delta.py
+++ b/numcodecs/delta.py
@@ -64,7 +64,10 @@ def encode(self, buf):
 
         # compute differences
         # using np.subtract for in-place operations
-        np.subtract(arr[1:], arr[0:-1], out=enc[1:])
+        if self.dtype == np.dtype("bool"):
+            np.not_equal(arr[1:], arr[0:-1], out=enc[1:])
+        else:
+            np.subtract(arr[1:], arr[0:-1], out=enc[1:])
 
         return enc
 
diff --git a/numcodecs/tests/test_delta.py b/numcodecs/tests/test_delta.py
index fb5714bb..9664efee 100644
--- a/numcodecs/tests/test_delta.py
+++ b/numcodecs/tests/test_delta.py
@@ -14,6 +14,7 @@
 # mix of shapes: 1D, 2D, 3D
 # mix of orders: C, F
 arrays = [
+    np.random.randint(0, 1, size=110, dtype='?').reshape(10, 11),
     np.arange(1000, dtype='<i4'),
     np.linspace(1000, 1001, 1000, dtype='<f4').reshape(100, 10),
     np.random.normal(loc=1000, scale=1, size=(10, 10, 10)).astype('<f8'),

From b2cccc1c76a8b100d11f5318b083ed55aa485100 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Thu, 10 Oct 2024 10:54:40 -0700
Subject: [PATCH 2/3] Simplify type check

This is a bit more succinct and gets to the core point. Namely
`arr.dtype` determines this code path.

Also comparing directly to `bool` works here. It is a bit faster as well
since we need not construct an `np.dtype` object.
---
 numcodecs/delta.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/numcodecs/delta.py b/numcodecs/delta.py
index 28a5233e..e86a0768 100644
--- a/numcodecs/delta.py
+++ b/numcodecs/delta.py
@@ -64,7 +64,7 @@ def encode(self, buf):
 
         # compute differences
         # using np.subtract for in-place operations
-        if self.dtype == np.dtype("bool"):
+        if arr.dtype == bool:
             np.not_equal(arr[1:], arr[0:-1], out=enc[1:])
         else:
             np.subtract(arr[1:], arr[0:-1], out=enc[1:])

From cf6fde0607854452dc8da5704a2dcce4da830f80 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Thu, 10 Oct 2024 11:05:25 -0700
Subject: [PATCH 3/3] Drop extraneous `0`s

---
 numcodecs/delta.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/numcodecs/delta.py b/numcodecs/delta.py
index e86a0768..f6307312 100644
--- a/numcodecs/delta.py
+++ b/numcodecs/delta.py
@@ -65,9 +65,9 @@ def encode(self, buf):
         # compute differences
         # using np.subtract for in-place operations
         if arr.dtype == bool:
-            np.not_equal(arr[1:], arr[0:-1], out=enc[1:])
+            np.not_equal(arr[1:], arr[:-1], out=enc[1:])
         else:
-            np.subtract(arr[1:], arr[0:-1], out=enc[1:])
+            np.subtract(arr[1:], arr[:-1], out=enc[1:])
 
         return enc