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author | Xiangrui Meng <meng@databricks.com> | 2014-11-03 12:24:24 -0800 |
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committer | Xiangrui Meng <meng@databricks.com> | 2014-11-03 12:24:47 -0800 |
commit | a68321400c1068449698d03cebd0fbf648627133 (patch) | |
tree | 58a5b8ef2aa5a8e30ee89bbfee8e207ac463e430 /python | |
parent | 76386e1a23c55a58c0aeea67820aab2bac71b24b (diff) | |
download | spark-a68321400c1068449698d03cebd0fbf648627133.tar.gz spark-a68321400c1068449698d03cebd0fbf648627133.tar.bz2 spark-a68321400c1068449698d03cebd0fbf648627133.zip |
[SPARK-4148][PySpark] fix seed distribution and add some tests for rdd.sample
The current way of seed distribution makes the random sequences from partition i and i+1 offset by 1.
~~~
In [14]: import random
In [15]: r1 = random.Random(10)
In [16]: r1.randint(0, 1)
Out[16]: 1
In [17]: r1.random()
Out[17]: 0.4288890546751146
In [18]: r1.random()
Out[18]: 0.5780913011344704
In [19]: r2 = random.Random(10)
In [20]: r2.randint(0, 1)
Out[20]: 1
In [21]: r2.randint(0, 1)
Out[21]: 0
In [22]: r2.random()
Out[22]: 0.5780913011344704
~~~
Note: The new tests are not for this bug fix.
Author: Xiangrui Meng <meng@databricks.com>
Closes #3010 from mengxr/SPARK-4148 and squashes the following commits:
869ae4b [Xiangrui Meng] move tests tests.py
c1bacd9 [Xiangrui Meng] fix seed distribution and add some tests for rdd.sample
(cherry picked from commit 3cca1962207745814b9d83e791713c91b659c36c)
Signed-off-by: Xiangrui Meng <meng@databricks.com>
Diffstat (limited to 'python')
-rw-r--r-- | python/pyspark/rdd.py | 3 | ||||
-rw-r--r-- | python/pyspark/rddsampler.py | 11 | ||||
-rw-r--r-- | python/pyspark/tests.py | 15 |
3 files changed, 20 insertions, 9 deletions
diff --git a/python/pyspark/rdd.py b/python/pyspark/rdd.py index 550c9dd805..4f025b9f11 100644 --- a/python/pyspark/rdd.py +++ b/python/pyspark/rdd.py @@ -316,9 +316,6 @@ class RDD(object): """ Return a sampled subset of this RDD (relies on numpy and falls back on default random generator if numpy is unavailable). - - >>> sc.parallelize(range(0, 100)).sample(False, 0.1, 2).collect() #doctest: +SKIP - [2, 3, 20, 21, 24, 41, 42, 66, 67, 89, 90, 98] """ assert fraction >= 0.0, "Negative fraction value: %s" % fraction return self.mapPartitionsWithIndex(RDDSampler(withReplacement, fraction, seed).func, True) diff --git a/python/pyspark/rddsampler.py b/python/pyspark/rddsampler.py index 528a181e89..f5c3cfd259 100644 --- a/python/pyspark/rddsampler.py +++ b/python/pyspark/rddsampler.py @@ -40,14 +40,13 @@ class RDDSamplerBase(object): def initRandomGenerator(self, split): if self._use_numpy: import numpy - self._random = numpy.random.RandomState(self._seed) + self._random = numpy.random.RandomState(self._seed ^ split) else: - self._random = random.Random(self._seed) + self._random = random.Random(self._seed ^ split) - for _ in range(0, split): - # discard the next few values in the sequence to have a - # different seed for the different splits - self._random.randint(0, 2 ** 32 - 1) + # mixing because the initial seeds are close to each other + for _ in xrange(10): + self._random.randint(0, 1) self._split = split self._rand_initialized = True diff --git a/python/pyspark/tests.py b/python/pyspark/tests.py index 37a128907b..253a471849 100644 --- a/python/pyspark/tests.py +++ b/python/pyspark/tests.py @@ -648,6 +648,21 @@ class RDDTests(ReusedPySparkTestCase): self.assertEquals(result.getNumPartitions(), 5) self.assertEquals(result.count(), 3) + def test_sample(self): + rdd = self.sc.parallelize(range(0, 100), 4) + wo = rdd.sample(False, 0.1, 2).collect() + wo_dup = rdd.sample(False, 0.1, 2).collect() + self.assertSetEqual(set(wo), set(wo_dup)) + wr = rdd.sample(True, 0.2, 5).collect() + wr_dup = rdd.sample(True, 0.2, 5).collect() + self.assertSetEqual(set(wr), set(wr_dup)) + wo_s10 = rdd.sample(False, 0.3, 10).collect() + wo_s20 = rdd.sample(False, 0.3, 20).collect() + self.assertNotEqual(set(wo_s10), set(wo_s20)) + wr_s11 = rdd.sample(True, 0.4, 11).collect() + wr_s21 = rdd.sample(True, 0.4, 21).collect() + self.assertNotEqual(set(wr_s11), set(wr_s21)) + class ProfilerTests(PySparkTestCase): |