Apache SystemML DML 不允许在函数中使用多个 return 值

Question

我正在尝试在 SystemlML 的 DML 中构建一个简单的 hello world 神经网络，但无法从 UDF 函数返回多个值。我受到 this code 成功运行的启发，但我无法弄清楚其中的区别：

根据 Berthold 的要求进行编辑（完整代码）：

script = """

#
sigmoid = function(matrix[double] z) return (matrix[double] z) {
    z = 1/(1+exp(-z))
}


sigmoidPrime = function(matrix[double] z) return (matrix[double] z) {
        #Gradient of sigmoid
        z = exp(-z)/(1+exp(-z))
}

X=matrix("3 5 5 1 10 2", rows=3, cols=2) 
inputLayerSize = 2
outputLayerSize = 1
hiddenLayerSize = 3

W1 = rand(rows=inputLayerSize,cols=hiddenLayerSize)
W2 = rand(rows=hiddenLayerSize,cols=outputLayerSize)

feedForward = function (matrix[double] X,
                        matrix[double] W1,
                        matrix[double] W2) return (matrix[double] z3,matrix[double] Y) {
    z2 =  X %*% W1
    a2 =  sigmoid(z2)
    z3 = (a2 %*% W2)
    Y = sigmoid(z3)
}

#feedForward = function (matrix[double] X,
#                        matrix[double] W1,
#                        matrix[double] W2) return (matrix[double] z2,matrix[double] z3,matrix[double] Y) {
#    z2 =  X %*% W1
#    a2 =  sigmoid(z2)
#    z3 = a2 %*% W2
#    Y = sigmoid(z3)
#    z2,z3,Y
#}

#gradient = function(matrix[double] X,
#                        matrix[double] W1,
#                        matrix[double] W2,
#                        matrix[double] Y) return (matrix[double] Y) {
#    #Compute derivative with respect to W and W2 for a given X and y:
#    z2,z3,yHat = feedForward(X,W1,W2)

#    delta3 = -(Y-yHat) * sigmoidPrime(z3)
#    dJdW2 = t(a2) %*% delta3

#    delta2 = (delta3 %*% t(W2))*sigmoidPrime(z2)
#    dJdW1 = t(X) %*% delta2  

#    return dJdW1, dJdW2
#}

Yhat=feedForward(X,W1,W2)
nrx = nrow(X)
ncx = ncol(X)
nrw1 = nrow(W1)
ncw1 = ncol(W1)
"""

如果我删除

matrix[double] z3

有效，否则我得到：

Caused by: org.apache.sysml.parser.LanguageException: ERROR: null -- line 22, column 0 -- Assignment statement cannot return multiple values

有什么想法吗？

Answer 1

SystemML 支持函数中的多个 return 值。参见 http://apache.github.io/systemml/dml-language-reference.html#user-defined-function-udf

以下 Python 示例 returns 2 个矩阵。

DMLstr = """
M1M2 = function( matrix[double] M) 
           return (matrix[double] M1, 
                   matrix[double] M2) {
    M1 = M + 1
    M2 = M + 2
}

X=matrix("3 5 5 1 10 2", rows=3, cols=2) 
[M1, M2] = M1M2 (X)
"""

[M1, M2] = ml.execute(dml(DMLstr).output('M1', 'M2')).get('M1','M2')

print M1.toNumPy()
print M2.toNumPy()

您的代码段未显示 "feedforward" 的调用。可以吗post?

Answer 2

您对 "feedForward" 的调用不正确，因为您 return 输出。更改为类似的内容：

[Yhat1, Yhat2]=feedForward(X,W1,W2)

Apache SystemML DML 不允许在函数中使用多个 return 值

Apache SystemML DML doesn't allow for multiple return values in function

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