Hi all, I found a significant bug in PySpark's sampling methods, due to a recent NumPy change (as of v1.9). I created a JIRA (https://issues.apache.org/jira/browse/SPARK-3995), but wanted to share here as well in case anyone hits it.
Steps to reproduce are: > foo = sc.parallelize(range(1000),5) > foo.takeSample(False, 10) Which returns: > PythonException: Traceback (most recent call last): > File > "/Users/freemanj11/code/spark-1.1.0-bin-hadoop1/python/pyspark/worker.py", > line 79, in main > serializer.dump_stream(func(split_index, iterator), outfile) > File > "/Users/freemanj11/code/spark-1.1.0-bin-hadoop1/python/pyspark/serializers.py", > line 196, in dump_stream > self.serializer.dump_stream(self._batched(iterator), stream) > File > "/Users/freemanj11/code/spark-1.1.0-bin-hadoop1/python/pyspark/serializers.py", > line 127, in dump_stream > for obj in iterator: > File > "/Users/freemanj11/code/spark-1.1.0-bin-hadoop1/python/pyspark/serializers.py", > line 185, in _batched > for item in iterator: > File > "/Users/freemanj11/code/spark-1.1.0-bin-hadoop1/python/pyspark/rddsampler.py", > line 116, in func > if self.getUniformSample(split) <= self._fraction: > File > "/Users/freemanj11/code/spark-1.1.0-bin-hadoop1/python/pyspark/rddsampler.py", > line 58, in getUniformSample > self.initRandomGenerator(split) > File > "/Users/freemanj11/code/spark-1.1.0-bin-hadoop1/python/pyspark/rddsampler.py", > line 44, in initRandomGenerator > self._random = numpy.random.RandomState(self._seed) > File "mtrand.pyx", line 610, in mtrand.RandomState.__init__ > (numpy/random/mtrand/mtrand.c:7397) > File "mtrand.pyx", line 646, in mtrand.RandomState.seed > (numpy/random/mtrand/mtrand.c:7697) > ValueError: Seed must be between 0 and 4294967295 The problem is that NumPy used to silently truncate random seeds larger than 2 ** 32, but now throws an error (due to this patch: https://github.com/numpy/numpy/commit/6b1a1205eac6fe5d162f16155d500765e8bca53c). And this reliably breaks our sampling. I’ll put a PR in shortly with the fix. — Jeremy ------------------------- jeremyfreeman.net @thefreemanlab
