我一直无法使用mxnet LinearRegressionOutput层获得合理的性能。
下面的自包含示例尝试执行简单多项式函数 ( y = x1 + x2^2 + x3^3) 的回归，其中包含少量随机噪声。
使用了此处给出的 mxnet 回归示例，以及包含隐藏层的稍微复杂的网络。
neuralnet下面的示例还使用and包训练回归网络nnet，从图中可以看出它的性能要好得多。
我意识到性能不佳的网络的答案是进行一些超参数调整，但是我尝试了一系列值，但性能没有任何改善。所以我有以下问题：
- 我的 mxnet 回归实现是否有错误？
- 有没有人有经验可以帮助我从 mxnet 获得合理的性能来解决像这里考虑的一个简单的回归问题？
- 还有其他人有性能良好的 mxnet 回归示例吗？
我的设置如下：
MXNet version: 0.7
R `sessionInfo()`: R version 3.3.2 (2016-10-31)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1
的回归结果不佳mxnet：
从这个可重现的例子：
## SIMPLE REGRESSION PROBLEM
# Check mxnet out-of-the-box performance VS neuralnet, and caret/nnet
library(mxnet)
library(neuralnet)
library(nnet)
library(caret)
library(tictoc)
library(reshape)
# Data definitions
nObservations <- 1000
noiseLvl <- 0.1
# Network config
nHidden <- 3
learnRate <- 2e-6
momentum <- 0.9
batchSize <- 20
nRound <- 1000
verbose <- FALSE
array.layout = "rowmajor"
# GENERATE DATA:
df <- data.frame(x1=runif(nObservations),
x2=runif(nObservations),
x3=runif(nObservations))
df$y <- df$x1 + df$x2^2 + df$x3^3 + noiseLvl*runif(nObservations)
# normalize data columns
# df <- scale(df)
# Seperate data into train/test
test.ind = seq(1, nObservations, 10) # 1 in 10 samples for testing
train.x = data.matrix(df[-test.ind, -which(colnames(df) %in% c("y"))])
train.y = df[-test.ind, "y"]
test.x = data.matrix(df[test.ind, -which(colnames(df) %in% c("y"))])
test.y = df[test.ind, "y"]
# Define mxnet network, following 5-minute regression example from here:
# http://mxnet-tqchen.readthedocs.io/en/latest//packages/r/fiveMinutesNeuralNetwork.html#regression
data <- mx.symbol.Variable("data")
label <- mx.symbol.Variable("label")
fc1 <- mx.symbol.FullyConnected(data, num_hidden=1, name="fc1")
lro1 <- mx.symbol.LinearRegressionOutput(data=fc1, label=label, name="lro")
# Train MXNET model
mx.set.seed(0)
tic("mxnet training 1")
mxModel1 <- mx.model.FeedForward.create(lro1, X=train.x, y=train.y,
eval.data=list(data=test.x, label=test.y),
ctx=mx.cpu(), num.round=nRound,
array.batch.size=batchSize,
learning.rate=learnRate, momentum=momentum,
eval.metric=mx.metric.rmse,
verbose=FALSE, array.layout=array.layout)
toc()
# Train network with a hidden layer
fc1 <- mx.symbol.FullyConnected(data, num_hidden=nHidden, name="fc1")
tanh1 <- mx.symbol.Activation(fc1, act_type="tanh", name="tanh1")
fc2 <- mx.symbol.FullyConnected(tanh1, num_hidden=1, name="fc2")
lro2 <- mx.symbol.LinearRegressionOutput(data=fc2, label=label, name="lro")
tic("mxnet training 2")
mxModel2 <- mx.model.FeedForward.create(lro2, X=train.x, y=train.y,
eval.data=list(data=test.x, label=test.y),
ctx=mx.cpu(), num.round=nRound,
array.batch.size=batchSize,
learning.rate=learnRate, momentum=momentum,
eval.metric=mx.metric.rmse,
verbose=FALSE, array.layout=array.layout)
toc()
# Train neuralnet model
mx.set.seed(0)
tic("neuralnet training")
nnModel <- neuralnet(y~x1+x2+x3, data=df[-test.ind, ], hidden=c(nHidden),
linear.output=TRUE, stepmax=1e6)
toc()
# Train caret model
mx.set.seed(0)
tic("nnet training")
nnetModel <- nnet(y~x1+x2+x3, data=df[-test.ind, ], size=nHidden, trace=F,
linout=TRUE)
toc()
# Check response VS targets on training data:
par(mfrow=c(2,2))
plot(train.y, compute(nnModel, train.x)$net.result,
main="neuralnet Train Fitting Fake Data", xlab="Target", ylab="Response")
abline(0,1, col="red")
plot(train.y, predict(nnetModel, train.x),
main="nnet Train Fitting Fake Data", xlab="Target", ylab="Response")
abline(0,1, col="red")
plot(train.y, predict(mxModel1, train.x, array.layout=array.layout),
main="MXNET (no hidden) Train Fitting Fake Data", xlab="Target",
ylab="Response")
abline(0,1, col="red")
plot(train.y, predict(mxModel2, train.x, array.layout=array.layout),
main="MXNET (with hidden) Train Fitting Fake Data", xlab="Target",
ylab="Response")
abline(0,1, col="red")
