Paddle/paddle/legacy/capi/examples/model_inference

Use C-API for Model Inference

There are several examples in this directory about how to use Paddle C-API for model inference.

Convert configuration file to protobuf binary.

Firstly, the user should convert Paddle's model configuration file into a protobuf binary file. In each example directory, there is a file named convert_protobin.sh. It will convert trainer_config.conf into trainer_config.bin.

The convert_protobin.sh is very simple, just invoke dump_config Python module to dump the binary file. The command line usages are:

python -m paddle.utils.dump_config YOUR_CONFIG_FILE 'CONFIG_EXTRA_ARGS' --binary > YOUR_CONFIG_FILE.bin

Initialize paddle

char* argv[] = {"--use_gpu=False"};
paddle_init(1, (char**)argv);

We must initialize global context before we invoke other interfaces in Paddle. The initialize commands just like the paddle_trainer command line arguments. paddle train --help, will show the list of arguments. The most important argument is use_gpu or not.

Load network and parameters

paddle_gradient_machine machine;
paddle_gradient_machine_create_for_inference(&machine, config_file_content, content_size));
paddle_gradient_machine_load_parameter_from_disk(machine, "./some_where_to_params"));

The gradient machine is a Paddle concept, which represents a neural network can be forwarded and backward. We can create a gradient machine fo model inference, and load the parameter files from disk.

Moreover, if we want to inference in multi-thread, we could create a thread local gradient machine which shared the same parameter by using paddle_gradient_machine_create_shared_param API. Please reference multi_thread as an example.

Create input

The input of a neural network is an arguments. The examples in this directory will show how to construct different types of inputs for prediction. Please look at dense, sparse_binary, sequence for details.

Get inference

After invoking paddle_gradient_machine_forward, we could get the output of the neural network. The value matrix of output arguments will store the neural network output values. If the output is a SoftmaxActivation, the value matrix are the probabilities of each input samples. The height of output matrix is number of sample. The width is the number of categories.