curiously I just found out that my CPU is much faster for predictions.
Doing inference with GPU is much slower then with CPU.
I have tf.keras (tf2) NN model with a simple dense layer:
input = tf.keras.layers.Input(shape=(100,), dtype='float32')
X = X = tf.keras.layers.Dense(2)(input)
model = tf.keras.Model(input,X)
#also initiialized with weights from a file
weights = np.load("weights.npy", allow_pickle=True )
model.layers[-1].set_weights(weights)
scores = model.predict_on_batch(data)
For 100 samples doing predictions I get:
2 s for GPU
0.07 s for CPU (!)
I am using a simple geforce mx150 with 2gb
I also tried the predict_on_batch(x) as someone suggested this as it is more faster than just predict. But here it is of same time.
Refer: Why does keras model predict slower after compile?
Has anyone an idea, what is going on there? What could be an issue possibly?
Using the GPU puts a lot of overhead to load data on the GPU memory (through the relatively slow PCI bus) and to get the results back.
In order for the GPU to be more efficient than the CPU, the model must to be very big, have plenty of data and use algorithms that can run fully inside the GPU, without requiring partial results to be moved back to the CPU.
The optimal configuration depends on the quantity of memory and of cores inside your GPU, so you must do some tests, but the following rules apply:
Your NN must have at least >10k parameters, training data set must have at least 10k records. Otherwise your overhead will probably kill the performances of GPU
When you model.fit, use a large batch_size (pay attention, the default is only 32), possibly to contain your whole dataset, or at least a multiple of 1024. Do some test to find the optimum for you.
For some GPUs, it might help performing computations in float16 instead of float32. Follow this tutorial to see how to activate it.
If your GPU has specific Tensor Cores, in order to use efficiently its hardware, several data must be multiples of 8. In the preceding tutorial, see at the paragraph "Ensuring GPU Tensor Cores are used" what parameters must be changed and how. In general, it's a bad idea to use layers which contain a number of neurons not multiple of 8.
Some type of layers, namely RNNs, have an architecture which cannot be solved directly by the GPU. In this case, data must be moved constantly back and forth to CPU and the speed is lost. If a RNN is really needed, Tensorflow v2 has an implementation of the LSTM layer which is optimized for GPU, but some limitations on the parameters are present: see this thread and the documetation.
If you are training a Reinforcement Learning, activate an Experience Replay and use a memory buffer for the experience which is at least >10x your batch_size. This way, you will activate the NN training only when a big bunch of data is ready.
Deactivate as much verbosity as possible
If everything is set up correctly, you should be able to train your model faster with GPU than with CPU.
GPU is good if you have compute-intensive tasks (large models) due to the overhead of copying your data and results between the host and GPU. In your case, the model is very small. It means it will take you longer to copy data than to predict. Even if the CPU is slower than the GPU, you don't have to copy the data, so it's ultimately faster.
Related
We are trying to train our model for object recognition using tensorflow. Since there are too many images (100GB), I guess our current GPU server (1*2080Ti) could not work. We may need to purchase a more powerful one, but I do not sure how to estimate how much GPU memory we need. Is there some approach to estimate the requirements? thanks!
Your 2080Ti would do just fine for your task. The GPU memory for DL tasks are dependent on many factors such as number of trainable parameters in the network, size of the images you are feeding, batch size, floating point type (FP16 or FP32) and number of activations and etc. I think you get confused about loading all of the images to GPU memory at once. We do not do that, instead we use minibatches of different sizes to fit all of the images and params into memory. Throw any kind of network to your 2080Ti and adjust batch size then your training will run smoothly. You could go with your 2080Ti or can get another or two increase training speed. This blogpost provides beautiful insights about creating optimal DL environments.
Suppose we have the following architecture:
Multiple CNN layers
RNN layer
(Time-distributed) Dense classification layer
We want to train this architecture now. Our fancy GPU is very fast at solving the CNN layers. Although using a lower clockrate, it can perform many convolutions in parallel, thus the speed. Our fancy CPU however is faster for the (very long) resulting time series, because the time steps cannot be parallelized, and the processing profits from the higher CPU clockrate. So the (supposedly) smart idea for execution would look like this:
Multiple CNN layers (run on GPU)
RNN layer (run on CPU)
(Time-distributed) Dense classification layer (run on GPU/CPU)
This lead me to two important questions:
Is it possible, with any of the frameworks mentioned in the title, to distribute certain layers to certain hardware, and how?
If it is possible, would the overhead for the additional memory operations, e.g. tranferring between GPU-/CPU-RAM, render the whole idea useless?
Basically, in Pytorch you can control the device on which variables/parameters reside. AFAIK, it is your responsibility to make sure that for each operation all the arguments reside on the same device: i.e., you cannot conv(x, y) where x is on GPU and y is on CPU.
This is done via pytorch's .to() method that moves a module/variable .to('cpu') or .to('cuda:0')
As Shai mentioned you can control this yourself in pytorch so in theory you can have parts of your model on different devices. You have then to move data between devices in your forward pass.
I think the overhead as you mentioned would make the performance worst. The cuda RNN implementation benefits greatly from running on a gpu anyways :)
I am running TensorFlow on a machine which has two GPUs, each with 3 GB memory. My batch size is only 2GB, and so can fit on one GPU. Is there any point in training with both GPUs (using CUDA_VISIBLE_DEVICES)? If I did, how would TensorFlow distribute the training?
With regards to memory: I assume that you mean that one data batch is 2GB. However, Tensorflow also requires memory to store variables as well as hidden layer results etc. (to compute gradients). For this reason it also depends on your specific model whether or not the memory will be enough. Your best bet would be to just try with one GPU and see if the program crashes due to memory errors.
With regards to distribution: Tensorflow doesn't do this automatically at all. Each op is placed on some device. By default, if you have any number of GPUs available, all GPU-compatible ops will be placed on the first GPU and the rest on the CPU. This is despite Tensorflow reserving all memory on all GPUs by default.
You should have a look at the GPU guide on the Tensorflow website. The most important thing is that you can use the with tf.device context manager to place ops on other GPUs. Using this, the idea would be to split your batch into X chunks (X = number of GPUs) and define your model on each device, each time taking the respective chunk as input and making sure to reuse variables.
If you are using tf.Estimator, there is some information in this question. It is very easy to do distributed execution here using just two simple wrappers, but I personally haven't been able to use it successfully (pretty slow and crashes randomly with a segfault).
I trained a neural network using a GPU (1080 ti). The training speed on GPU is far better than using CPU.
Currently, I want to serve this model using TensorFlow Serving. I just interested to know if using GPU in the serving process has a same impact on performance?
Since the training apply on batches but inferencing (serving) uses asynchronous requests, do you suggest using GPU in serving a model using TensorFlow serving?
You still need to do a lot of tensor operations on the graph to predict something. So GPU still provides performance improvement for inference. Take a look at this nvidia paper, they have not tested their stuff on TF, but it is still relevant:
Our results show that GPUs provide state-of-the-art inference
performance and energy efficiency, making them the platform of choice
for anyone wanting to deploy a trained neural network in the field. In
particular, the Titan X delivers between 5.3 and 6.7 times higher
performance than the 16-core Xeon E5 CPU while achieving 3.6 to 4.4
times higher energy efficiency.
The short answer is yes, you'll get roughly the same speedup for running on the GPU after training. With a few minor qualifications.
You're running 2 passes over the data in training, which all happens on the GPU, during the feedforward inference you're doing less work, so there will be more time spent transferring data to the GPU memory relative to computations than in training. This is probably a minor difference though. And you can now asynchronously load the GPU if that's an issue (https://github.com/tensorflow/tensorflow/issues/7679).
Whether you'll actually need a GPU to do inference depends on your workload. If your workload isn't overly demanding you might get away with using the CPU anyway, after all, the computation workload is less than half, per sample, so consider the number of requests per second you'll need to serve and test out whether you overload your CPU to achieve that. If you do, time to get the GPU out!
I'm working on code that trains a relatively large RNN (128 cell LSTM and some added layers). The main process is maxing out a core on the CPU, and I'm wondering if this is normal or whether I can optimize it. During the training loop (session.run calls) it's using about 60-70% GPU load while using 100% CPU load on one core. Note that data sampling work is already being done concurrently on other cores, so it's just the updating of the model parameters. Is this regular for such applications in TensorFlow or should the CPU load be much lower, while using the full capacity of the GPU?
We don't have full documentation on it yet, but you can take a look at the profiling information to see if it gives you more of an idea of where the time is going:
https://github.com/tensorflow/tensorflow/issues/1824#issuecomment-225754659
I think RNN cell have two input, it must wait for those two direction input when traning data, in other word, it optimize parallelism don't as easy as CNN. You can use a big batch size to improve the GPU utilization rate, but maybe cause other problem like that paper On Large-Batch Training for Deep Learning: Generalization Gap and Sharp Minima.