Improve write performance of shards

bench/write_shard.py

@@ -0,0 +1,66 @@
+import itertools
+import os.path
+import shutil
+import sys
+import tempfile
+import timeit
+
+import line_profiler
+import numpy as np
+
+import zarr
+import zarr.codecs
+import zarr.codecs.sharding
+
+if __name__ == "__main__":
+    sys.path.insert(0, "..")
+
+    # setup
+    with tempfile.TemporaryDirectory() as path:
+
+        ndim = 3
+        opt = {
+            'shape': [1024]*ndim,
+            'chunks': [128]*ndim,
+            'shards': [512]*ndim,
+            'dtype': np.float64,
+        }
+
+        store = zarr.storage.LocalStore(path)
+        z = zarr.create_array(store, **opt)
+        print(z)
+
+        def cleanup() -> None:
+            for elem in os.listdir(path):
+                elem = os.path.join(path, elem)
+                if not elem.endswith(".json"):
+                    if os.path.isdir(elem):
+                        shutil.rmtree(elem)
+                    else:
+                        os.remove(elem)
+
+        def write() -> None:
+            wchunk = [512]*ndim
+            nwchunks = [n//s for n, s in zip(opt['shape'], wchunk, strict=True)]
+            for shard in itertools.product(*(range(n) for n in nwchunks)):
+                slicer = tuple(
+                    slice(i*n, (i+1)*n)
+                    for i, n in zip(shard, wchunk, strict=True)
+                )
+                d = np.random.rand(*wchunk).astype(opt['dtype'])
+                z[slicer] = d
+
+        print("*" * 79)
+
+        # time
+        vars = {"write": write, "cleanup": cleanup, "z": z, "opt": opt}
+        t = timeit.repeat("write()", "cleanup()", repeat=2, number=1, globals=vars)
+        print(t)
+        print(min(t))
+        print(z)
+
+        # profile
+        # f = zarr.codecs.sharding.ShardingCodec._encode_partial_single
+        # profile = line_profiler.LineProfiler(f)
+        # profile.run("write()")
+        # profile.print_stats()

src/zarr/codecs/sharding.py

@@ -202,7 +202,7 @@ def create_empty(
             buffer_prototype = default_buffer_prototype()
         index = _ShardIndex.create_empty(chunks_per_shard)
         obj = cls()
-        obj.buf = buffer_prototype.buffer.create_zero_length()
+        obj.buf = buffer_prototype.buffer.Delayed.create_zero_length()
         obj.index = index
         return obj
 
@@ -251,7 +251,7 @@ def create_empty(
         if buffer_prototype is None:
             buffer_prototype = default_buffer_prototype()
         obj = cls()
-        obj.buf = buffer_prototype.buffer.create_zero_length()
+        obj.buf = buffer_prototype.buffer.Delayed.create_zero_length()
         obj.index = _ShardIndex.create_empty(chunks_per_shard)
         return obj
 

src/zarr/core/buffer/core.py

@@ -502,6 +502,153 @@
     nd_buffer: type[NDBuffer]
 
 
+class DelayedBuffer(Buffer):
+    """
+    A Buffer that is the virtual concatenation of other buffers.
+    """
+    _BufferImpl: type
+    _concatenate: callable
+
+    def __init__(self, array: NDArrayLike | list[NDArrayLike] | None) -> None:
+        if array is None:
+            self._data_list = []
+        elif isinstance(array, list):
+            self._data_list = list(array)
+        else:
+            self._data_list = [array]
+        for array in self._data_list:
+            if array.ndim != 1:
+                raise ValueError("array: only 1-dim allowed")
+            if array.dtype != np.dtype("b"):
+                raise ValueError("array: only byte dtype allowed")
+
+    @property
+    def _data(self) -> npt.NDArray[Any]:
+        return type(self)._concatenate(self._data_list)
+
+    @classmethod
+    def from_buffer(cls, buffer: Buffer) -> Self:
+        if isinstance(buffer, cls):
+            return cls(buffer._data_list)
+        else:
+            return cls(buffer._data)
+
+    def __add__(self, other: Buffer) -> Self:
+        if isinstance(other, self.__class__):
+            return self.__class__(self._data_list + other._data_list)
+        else:
+            return self.__class__(self._data_list + [other._data])
+
+    def __radd__(self, other: Buffer) -> Self:
+        if isinstance(other, self.__class__):
+            return self.__class__(other._data_list + self._data_list)
+        else:
+            return self.__class__([other._data] + self._data_list)
+
+    def __len__(self) -> int:
+        return sum(map(len, self._data_list))
+
+    def __getitem__(self, key: slice) -> Self:
+        check_item_key_is_1d_contiguous(key)
+        start, stop = key.start, key.stop
+        this_len = len(self)
+        if start is None:
+            start = 0
+        if start < 0:
+            start = this_len + start
+        if stop is None:
+            stop = this_len
+        if stop < 0:
+            stop = this_len + stop
+        if stop > this_len:
+            stop = this_len
+        if stop <= start:
+            return Buffer.from_buffer(b'')
+
+        new_list = []
+        offset = 0
+        found_last = False
+        for chunk in self._data_list:
+            chunk_size = len(chunk)
+            skip = False
+            if 0 <= start - offset < chunk_size:
+                # first chunk
+                if stop - offset <= chunk_size:
+                    # also last chunk
+                    chunk = chunk[start-offset:stop-offset]
+                    found_last = True
+                else:
+                    chunk = chunk[start-offset:]
+            elif 0 <= stop - offset <= chunk_size:
+                # last chunk
+                chunk = chunk[:stop-offset]
+                found_last = True
+            elif chunk_size <= start - offset:
+                # before first chunk
+                skip = True
+            else:
+                # middle chunk
+                pass
+
+            if not skip:
+                new_list.append(chunk)
+            if found_last:
+                break
+            offset += chunk_size
+        assert sum(map(len, new_list)) == stop - start
+        return self.__class__(new_list)
+
+    def __setitem__(self, key: slice, value: Any) -> None:
+        # This assumes that `value` is a broadcasted array
+        check_item_key_is_1d_contiguous(key)
+        start, stop = key.start, key.stop
+        if start is None:
+            start = 0
+        if start < 0:
+            start = len(self) + start
+        if stop is None:
+            stop = len(self)
+        if stop < 0:
+            stop = len(self) + stop
+        if stop <= start:
+            return
+
+        offset = 0
+        found_last = False
+        value = memoryview(np.asanyarray(value))
+        for chunk in self._data_list:
+            chunk_size = len(chunk)
+            skip = False
+            if 0 <= start - offset < chunk_size:
+                # first chunk
+                if stop - offset <= chunk_size:
+                    # also last chunk
+                    chunk = chunk[start-offset:stop-offset]
+                    found_last = True
+                else:
+                    chunk = chunk[start-offset:]
+            elif 0 <= stop - offset <= chunk_size:
+                # last chunk
+                chunk = chunk[:stop-offset]
+                found_last = True
+            elif chunk_size <= start - offset:
+                # before first chunk
+                skip = True
+            else:
+                # middle chunk
+                pass
+
+            if not skip:
+                chunk[:] = value[:len(chunk)]
+                value = value[len(chunk):]
+                if len(value) == 0:
+                    # nothing left to write
+                    break
+            if found_last:
+                break
+            offset += chunk_size
+
+
 # The default buffer prototype used throughout the Zarr codebase.
 def default_buffer_prototype() -> BufferPrototype:
     from zarr.registry import (

src/zarr/core/buffer/cpu.py

@@ -185,6 +185,39 @@
         self._data.__setitem__(key, value)
 
 
+class DelayedBuffer(core.DelayedBuffer, Buffer):
+    """
+    A Buffer that is the virtual concatenation of other buffers.
+    """
+    _BufferImpl = Buffer
+    _concatenate = np.concatenate
+
+    def __init__(self, array: NDArrayLike | list[NDArrayLike] | None) -> None:
+        core.DelayedBuffer.__init__(self, array)
+        self._data_list = list(map(np.asanyarray, self._data_list))
+
+    @classmethod
+    def create_zero_length(cls) -> Self:
+        return cls(np.array([], dtype="b"))
+
+    @classmethod
+    def from_buffer(cls, buffer: core.Buffer) -> Self:
+        if isinstance(buffer, cls):
+            return cls(buffer._data_list)
+        else:
+            return cls(buffer._data)
+
+    @classmethod
+    def from_bytes(cls, bytes_like: BytesLike) -> Self:
+        return cls(np.asarray(bytes_like, dtype="b"))
+
+    def as_numpy_array(self) -> npt.NDArray[Any]:
+        return np.asanyarray(self._data)
+
+
+Buffer.Delayed = DelayedBuffer
+
+
 def as_numpy_array_wrapper(
     func: Callable[[npt.NDArray[Any]], bytes], buf: core.Buffer, prototype: core.BufferPrototype
 ) -> core.Buffer:

src/zarr/core/buffer/gpu.py

@@ -218,6 +218,39 @@
         self._data.__setitem__(key, value)
 
 
+class DelayedBuffer(core.DelayedBuffer, Buffer):
+    """
+    A Buffer that is the virtual concatenation of other buffers.
+    """
+    _BufferImpl = Buffer
+    _concatenate = getattr(cp, 'concatenate', None)
+
+    def __init__(self, array: NDArrayLike | list[NDArrayLike] | None) -> None:
+        core.DelayedBuffer.__init__(self, array)
+        self._data_list = list(map(cp.asarray, self._data_list))
+
+    @classmethod
+    def create_zero_length(cls) -> Self:
+        return cls(np.array([], dtype="b"))
+
+    @classmethod
+    def from_buffer(cls, buffer: core.Buffer) -> Self:
+        if isinstance(buffer, cls):
+            return cls(buffer._data_list)
+        else:
+            return cls(buffer._data)
+
+    @classmethod
+    def from_bytes(cls, bytes_like: BytesLike) -> Self:
+        return cls(np.asarray(bytes_like, dtype="b"))
+
+    def as_numpy_array(self) -> npt.NDArray[Any]:
+        return np.asanyarray(self._data)
+
+
+Buffer.Delayed = DelayedBuffer
+
+
 buffer_prototype = BufferPrototype(buffer=Buffer, nd_buffer=NDBuffer)
 
 register_buffer(Buffer)