.rst .pdf

Primitive Example

This C++ API example demonstrates how to create and execute an PReLU primitive in forward training propagation mode.

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#include <algorithm>
#include <cmath>
#include <string>
#include <vector>

#include "dnnl.hpp"
#include "example_utils.hpp"

using namespace dnnl;

using tag = memory::format_tag;
using dt = memory::data_type;

void prelu_example(dnnl::engine::kind engine_kind) {

    // Create execution dnnl::engine.
    dnnl::engine engine(engine_kind, 0);

    // Create dnnl::stream.
    dnnl::stream engine_stream(engine);

    // Tensor dimensions.
    const memory::dim N = 3, // batch size
            IC = 3, // channels
            IH = 227, // tensor height
            IW = 227; // tensor width

    // Source (src), weights and destination (dst) tensors dimensions.
    const memory::dims src_dims = {N, IC, IH, IW};
    const memory::dims weights_dims = {N, IC, IH, IW};
    const memory::dims dst_dims = {N, IC, IH, IW};

    // Allocate buffers. In this example, out-of-place primitive execution is
    // demonstrated since both src and dst are required for later backward
    // propagation.
    std::vector<float> src_data(product(src_dims));
    std::vector<float> weights_data(product(weights_dims));
    std::vector<float> dst_data(product(dst_dims));

    // Initialize src tensor.
    std::generate(src_data.begin(), src_data.end(), []() {
        static int i = 0;
        return std::cos(i++ / 10.f);
    });

    // Initialize weights tensor.
    std::fill(weights_data.begin(), weights_data.end(), 0.3f);

    // Create memory objects for tensor data (src, weights, dst). In this
    // example, NCHW layout is assumed for src, weights and dst.
    auto user_src_mem = memory({src_dims, dt::f32, tag::nchw}, engine);
    auto user_weights_mem = memory({weights_dims, dt::f32, tag::nchw}, engine);
    auto user_dst_mem = memory({dst_dims, dt::f32, tag::nchw}, engine);

    // Create memory descriptors for the primitive. Src tag is set
    // to match src memory object. Setting weights tag to format_tag::any
    // enables the PReLU primitive to choose memory layout for an optimized
    // primitive implementation, and that layout may differ from the one
    // provided by the user.
    auto src_md = memory::desc(src_dims, dt::f32, tag::nchw);
    auto weights_md = memory::desc(weights_dims, dt::f32, tag::any);

    // Write data to memory object's handle.
    write_to_dnnl_memory(src_data.data(), user_src_mem);
    write_to_dnnl_memory(weights_data.data(), user_weights_mem);

    // Create operation descriptor.
    auto prelu_d = prelu_forward::desc(
            prop_kind::forward_training, src_md, weights_md);

    // Create primitive descriptor.
    auto prelu_pd = prelu_forward::primitive_desc(prelu_d, engine);

    // For now, assume that the weights memory layout generated
    // by the primitive and the one provided by the user are identical.
    auto prelu_weights_mem = user_weights_mem;

    // Reorder the data in case the weights memory layout generated by
    // the primitive and the one provided by the user are different. In this
    // case, we create additional memory object with internal buffers that will
    // contain the reordered data.
    if (prelu_pd.weights_desc() != user_weights_mem.get_desc()) {
        prelu_weights_mem = memory(prelu_pd.weights_desc(), engine);
        reorder(user_weights_mem, prelu_weights_mem)
                .execute(engine_stream, user_weights_mem, prelu_weights_mem);
    }

    // Create the primitive.
    auto prelu_prim = prelu_forward(prelu_pd);

    // Primitive arguments.
    std::unordered_map<int, memory> prelu_args;
    prelu_args.insert({DNNL_ARG_SRC, user_src_mem});
    prelu_args.insert({DNNL_ARG_WEIGHTS, prelu_weights_mem});
    prelu_args.insert({DNNL_ARG_DST, user_dst_mem});

    // Primitive execution: PReLU.
    prelu_prim.execute(engine_stream, prelu_args);

    // Wait for the computation to finalize.
    engine_stream.wait();

    // Read data from memory object's handle.
    read_from_dnnl_memory(dst_data.data(), user_dst_mem);
}

int main(int argc, char **argv) {
    return handle_example_errors(prelu_example, parse_engine_kind(argc, argv));
}