chore: import upstream snapshot with attribution

tools/distpartitioning/array_readwriter/numpy_array.py

@@ -0,0 +1,26 @@
+import logging
+
+import numpy as np
+from numpy.lib.format import open_memmap
+
+from .registry import register_array_parser
+
+
+@register_array_parser("numpy")
+class NumpyArrayParser(object):
+    def __init__(self):
+        pass
+
+    def read(self, path):
+        logging.debug("Reading from %s using numpy format" % path)
+        arr = np.load(path, mmap_mode="r")
+        logging.debug("Done reading from %s" % path)
+        return arr
+
+    def write(self, path, arr):
+        logging.debug("Writing to %s using numpy format" % path)
+        # np.save would load the entire memmap array up into CPU.  So we manually open
+        # an empty npy file with memmap mode and manually flush it instead.
+        new_arr = open_memmap(path, mode="w+", dtype=arr.dtype, shape=arr.shape)
+        new_arr[:] = arr[:]
+        logging.debug("Done writing to %s" % path)