utils: extend to_chunks functionality, can specify number of chunks or length of chunk

dvc/remote/base.py

@@ -636,7 +636,7 @@ class RemoteBASE(object):
         if self.no_traverse and hasattr(self, "batch_exists"):
             with ThreadPoolExecutor(max_workers=self.JOBS) as executor:
                 path_infos = [self.checksum_to_path_info(x) for x in checksums]
-                chunks = to_chunks(path_infos, self.JOBS)
+                chunks = to_chunks(path_infos, num_chunks=self.JOBS)
                 results = executor.map(exists_with_progress, chunks)
                 in_remote = itertools.chain.from_iterable(results)
                 ret = list(itertools.compress(checksums, in_remote))

dvc/remote/local/__init__.py

@@ -360,9 +360,9 @@ class RemoteLOCAL(RemoteBASE):
             from_infos = cache
 
         return (
-            to_chunks(from_infos, jobs),
-            to_chunks(to_infos, jobs),
-            to_chunks(names, jobs),
+            to_chunks(from_infos, num_chunks=jobs),
+            to_chunks(to_infos, num_chunks=jobs),
+            to_chunks(names, num_chunks=jobs),
         )
 
     def _process(

dvc/remote/ssh/__init__.py

@@ -157,7 +157,7 @@ class RemoteSSH(RemoteBASE):
 
                 with ThreadPoolExecutor(max_workers=max_workers) as executor:
                     paths = [path_info.path for path_info in path_infos]
-                    chunks = to_chunks(paths, max_workers)
+                    chunks = to_chunks(paths, num_chunks=max_workers)
                     chunks_and_channels = zip(chunks, channels)
                     outcome = executor.map(_exists, chunks_and_channels)
                     results = list(itertools.chain.from_iterable(outcome))

dvc/state.py

@@ -7,7 +7,7 @@ import sqlite3
 import logging
 
 from dvc.config import Config
-from dvc.utils import remove, current_timestamp, relpath, chunk
+from dvc.utils import remove, current_timestamp, relpath, to_chunks
 from dvc.exceptions import DvcException
 from dvc.utils.fs import get_mtime_and_size, get_inode
 from dvc.utils.compat import fspath_py35
@@ -450,7 +450,9 @@ class State(StateBase):  # pylint: disable=too-many-instance-attributes
                 remove(path)
                 unused.append(relpath)
 
-        for chunk_unused in chunk(unused, SQLITE_MAX_VARIABLES_NUMBER):
+        for chunk_unused in to_chunks(
+            unused, chunk_size=SQLITE_MAX_VARIABLES_NUMBER
+        ):
             cmd = "DELETE FROM {} WHERE path IN ({})".format(
                 self.LINK_STATE_TABLE, ",".join(["?"] * len(chunk_unused))
             )

dvc/utils/__init__.py

@@ -183,16 +183,33 @@ def remove(path):
             raise
 
 
-def to_chunks(l, jobs):
-    n = int(math.ceil(len(l) / jobs))
+def _split(list_to_split, chunk_size):
+    return [
+        list_to_split[i : i + chunk_size]
+        for i in range(0, len(list_to_split), chunk_size)
+    ]
 
-    if len(l) == 1:
-        return [l]
 
-    if n == 0:
-        n = 1
+def _to_chunks_by_chunks_number(list_to_split, num_chunks):
+    chunk_size = int(math.ceil(float(len(list_to_split)) / num_chunks))
 
-    return [l[x : x + n] for x in range(0, len(l), n)]
+    if len(list_to_split) == 1:
+        return [list_to_split]
+
+    if chunk_size == 0:
+        chunk_size = 1
+
+    return _split(list_to_split, chunk_size)
+
+
+def to_chunks(list_to_split, num_chunks=None, chunk_size=None):
+    if (num_chunks and chunk_size) or (not num_chunks and not chunk_size):
+        raise ValueError(
+            "One and only one of 'num_chunks', 'chunk_size' must be defined"
+        )
+    if chunk_size:
+        return _split(list_to_split, chunk_size)
+    return _to_chunks_by_chunks_number(list_to_split, num_chunks)
 
 
 # NOTE: Check if we are in a bundle
@@ -382,8 +399,3 @@ def relpath(path, start=os.curdir):
     ):
         return path
     return os.path.relpath(path, start)
-
-
-def chunk(iterable, chunk_size):
-    for i in range(0, len(iterable), chunk_size):
-        yield iterable[i : i + chunk_size]

tests/unit/utils/test_utils.py

@@ -1,16 +1,30 @@
 import pytest
 
-from dvc.utils import chunk
+from dvc.utils import to_chunks
 
 
 @pytest.mark.parametrize(
-    "list_to_chunk, chunk_size, expected_chunks",
-    [
-        ([1, 2, 3, 4], 1, [[1], [2], [3], [4]]),
-        ([1, 2, 3, 4], 2, [[1, 2], [3, 4]]),
-        ([1, 2, 3, 4], 3, [[1, 2, 3], [4]]),
-    ],
+    "chunk_size, expected_chunks",
+    [(1, [[1], [2], [3], [4]]), (2, [[1, 2], [3, 4]]), (3, [[1, 2, 3], [4]])],
 )
-def test_chunk(list_to_chunk, chunk_size, expected_chunks):
-    result = list(chunk(list_to_chunk, chunk_size))
+def test_to_chunks_chunk_size(chunk_size, expected_chunks):
+    list_to_chunk = [1, 2, 3, 4]
+    result = list(to_chunks(list_to_chunk, chunk_size=chunk_size))
+    assert result == expected_chunks
+
+
+@pytest.mark.parametrize("num_chunks, chunk_size", [(1, 2), (None, None)])
+def test_to_chunks_should_raise(num_chunks, chunk_size):
+    list_to_chunk = [1, 2, 3]
+    with pytest.raises(ValueError):
+        to_chunks(list_to_chunk, num_chunks, chunk_size)
+
+
+@pytest.mark.parametrize(
+    "num_chunks, expected_chunks",
+    [(4, [[1], [2], [3], [4]]), (3, [[1, 2], [3, 4]]), (2, [[1, 2], [3, 4]])],
+)
+def test_to_chunks_num_chunks(num_chunks, expected_chunks):
+    list_to_chunk = [1, 2, 3, 4]
+    result = to_chunks(list_to_chunk, num_chunks=num_chunks)
     assert result == expected_chunks