我们正在尝试使用 Spark 上的 MLLIB 在 python 中训练具有指定初始模型的高斯混合模型 (GMM)。pyspark 的 Doc 1.5.1 说我们应该使用 GaussianMixtureModel 对象作为 GaussianMixture.train 方法的“initialModel”参数的输入。在创建我们自己的初始模型（例如，计划使用 Kmean 结果）之前，我们只是想测试这个场景。因此，我们尝试使用来自第一次训练的输出的 GaussianMixtureModel 初始化第二次训练。但是这个简单的场景会引发错误。你能帮我们确定这里发生了什么吗？非常感谢纪尧姆
PS：我们用 hadoop 2.6 运行 (py) spark 1.5.1
以下是简单的场景代码和错误：
from pyspark.mllib.clustering import GaussianMixture
from numpy import array
import sys
import os
import pyspark
### Local default options
K=2 # "k" (int) Set the number of Gaussians in the mixture model. Default: 2
convergenceTol=1e-3 # "convergenceTol" (double) Set the largest change in log-likelihood at which convergence is considered to have occurred.
maxIterations=100 # "maxIterations" (int) Set the maximum number of iterations to run. Default: 100
seed=None # "seed" (long) Set the random seed
initialModel=None
### Load and parse the sample data
data = sc.textFile("gmm_data.txt") # Data from the dummy set here: data/mllib/gmm_data.txt
parsedData = data.map(lambda line: array([float(x) for x in line.strip().split(' ')]))
print type(parsedData)
print type(parsedData.first())
### 1st training: Build the GMM
gmm = GaussianMixture.train(parsedData, K, convergenceTol,
maxIterations, seed, initialModel)
# output parameters of model
for i in range(2):
print ("weight = ", gmm.weights[i], "mu = ", gmm.gaussians[i].mu,
"sigma = ", gmm.gaussians[i].sigma.toArray())
### 2nd training: Re-build a GMM using an initial model
initialModel = gmm
print type(initialModel)
gmm = GaussianMixture.train(parsedData, K, convergenceTol, maxIterations, seed, initialModel)
这是带有错误的输出：
<class 'pyspark.rdd.PipelinedRDD'>
<type 'numpy.ndarray'>
('weight = ', 0.51945003367044018, 'mu = ', DenseVector([-0.1045,
0.0429]), 'sigma = ', array([[ 4.90706817, -2.00676881],
[-2.00676881, 1.01143891]]))
('weight = ', 0.48054996632955982, 'mu = ', DenseVector([0.0722,
0.0167]), 'sigma = ', array([[ 4.77975653, 1.87624558],
[ 1.87624558, 0.91467242]]))
<class 'pyspark.mllib.clustering.GaussianMixtureModel'>
---------------------------------------------------------------------------
Py4JJavaError Traceback (most recent call last)
<ipython-input-30-0008fe75eb61> in <module>()
33 initialModel = gmm
34 print type(initialModel)
---> 35 gmm = GaussianMixture.train(parsedData, K, convergenceTol,
maxIterations, seed, initialModel) #
/opt/spark/spark-1.5.1-bin-hadoop2.6/python/pyspark/mllib/clustering.pyc
in train(cls, rdd, k, convergenceTol, maxIterations, seed,
initialModel)
306 java_model =
callMLlibFunc("trainGaussianMixtureModel",
rdd.map(_convert_to_vector),
307 k, convergenceTol,
maxIterations, seed,
--> 308 initialModelWeights,
initialModelMu, initialModelSigma)
309 return GaussianMixtureModel(java_model)
310
/opt/spark/spark-1.5.1-bin-hadoop2.6/python/pyspark/mllib/common.pyc
in callMLlibFunc(name, *args)
128 sc = SparkContext._active_spark_context
129 api = getattr(sc._jvm.PythonMLLibAPI(), name)
--> 130 return callJavaFunc(sc, api, *args)
131
132
/opt/spark/spark-1.5.1-bin-hadoop2.6/python/pyspark/mllib/common.pyc
in callJavaFunc(sc, func, *args)
120 def callJavaFunc(sc, func, *args):
121 """ Call Java Function """
--> 122 args = [_py2java(sc, a) for a in args]
123 return _java2py(sc, func(*args))
124
/opt/spark/spark-1.5.1-bin-hadoop2.6/python/pyspark/mllib/common.pyc
in _py2java(sc, obj)
86 else:
87 data = bytearray(PickleSerializer().dumps(obj))
---> 88 obj = sc._jvm.SerDe.loads(data)
89 return obj
90
/opt/spark/spark-1.5.1-bin-hadoop2.6/python/lib/py4j-0.8.2.1-src.zip/py4j/java_gateway.py
in __call__(self, *args)
536 answer = self.gateway_client.send_command(command)
537 return_value = get_return_value(answer, self.gateway_client,
--> 538 self.target_id, self.name)
539
540 for temp_arg in temp_args:
/opt/spark/spark-1.5.1-bin-hadoop2.6/python/pyspark/sql/utils.pyc in
deco(*a, **kw)
34 def deco(*a, **kw):
35 try:
---> 36 return f(*a, **kw)
37 except py4j.protocol.Py4JJavaError as e:
38 s = e.java_exception.toString()
/opt/spark/spark-1.5.1-bin-hadoop2.6/python/lib/py4j-0.8.2.1-src.zip/py4j/protocol.py
in get_return_value(answer, gateway_client, target_id, name)
298 raise Py4JJavaError(
299 'An error occurred while calling {0}{1}{2}.\n'.
--> 300 format(target_id, '.', name), value)
301 else:
302 raise Py4JError(
Py4JJavaError: An error occurred while calling
z:org.apache.spark.mllib.api.python.SerDe.loads.
: net.razorvine.pickle.PickleException: expected zero arguments for
construction of ClassDict (for numpy.core.multiarray._reconstruct)
at net.razorvine.pickle.objects.ClassDictConstructor.construct(ClassDictConstructor.java:23)
at net.razorvine.pickle.Unpickler.load_reduce(Unpickler.java:701)
at net.razorvine.pickle.Unpickler.dispatch(Unpickler.java:171)
at net.razorvine.pickle.Unpickler.load(Unpickler.java:85)
at net.razorvine.pickle.Unpickler.loads(Unpickler.java:98)
at org.apache.spark.mllib.api.python.SerDe$.loads(PythonMLLibAPI.scala:1462)
at org.apache.spark.mllib.api.python.SerDe.loads(PythonMLLibAPI.scala)
at sun.reflect.GeneratedMethodAccessor31.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:231)
at py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:379)
at py4j.Gateway.invoke(Gateway.java:259)
at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:133)
at py4j.commands.CallCommand.execute(CallCommand.java:79)
at py4j.GatewayConnection.run(GatewayConnection.java:207)
at java.lang.Thread.run(Thread.java:745)