RNN int8 inference example

Intel® oneAPI Deep Neural Network Developer Guide and Reference

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ID 768875

Date 6/20/2024

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RNN int8 inference example

This C++ API example demonstrates how to build GNMT model inference.

Example code: cpu_rnn_inference_int8.cpp

For the encoder we use:

one primitive for the bidirectional layer of the encoder
one primitive for all remaining unidirectional layers in the encoder For the decoder we use:
one primitive for the first iteration
one primitive for all subsequent iterations in the decoder. Note that in this example, this primitive computes the states in place.
the attention mechanism is implemented separately as there is no support for the context vectors in oneDNN yet

Initialize a CPU engine and stream. The last parameter in the call represents the index of the engine.

auto cpu_engine = engine(engine::kind::cpu, 0);
stream s(cpu_engine);

Declare encoder net and decoder net

std::vector<primitive> encoder_net, decoder_net;
std::vector<std::unordered_map<int, memory>> encoder_net_args,
        decoder_net_args;

std::vector<float> net_src(batch * src_seq_length_max * feature_size, 0.1f);
std::vector<float> net_dst(batch * tgt_seq_length_max * feature_size, 0.1f);

Quantization factors for f32 data

std::vector<float> weights_scales(lstm_n_gates * feature_size);
// assign halves of vector with arbitrary values
const dim_t scales_half = lstm_n_gates * feature_size / 2;
std::fill(
        weights_scales.begin(), weights_scales.begin() + scales_half, 30.f);
std::fill(
        weights_scales.begin() + scales_half, weights_scales.end(), 65.5f);

Encoder

Initialize Encoder Memory

memory::dims enc_bidir_src_layer_tz
        = {src_seq_length_max, batch, feature_size};
memory::dims enc_bidir_weights_layer_tz
        = {enc_bidir_n_layers, 2, feature_size, lstm_n_gates, feature_size};
memory::dims enc_bidir_weights_iter_tz
        = {enc_bidir_n_layers, 2, feature_size, lstm_n_gates, feature_size};
memory::dims enc_bidir_bias_tz
        = {enc_bidir_n_layers, 2, lstm_n_gates, feature_size};
memory::dims enc_bidir_dst_layer_tz
        = {src_seq_length_max, batch, 2 * feature_size};

Encoder: 1 bidirectional layer and 7 unidirectional layers

Create the memory for user data

auto user_enc_bidir_src_layer_md = memory::desc({enc_bidir_src_layer_tz},
        memory::data_type::f32, memory::format_tag::tnc);

auto user_enc_bidir_wei_layer_md
        = memory::desc({enc_bidir_weights_layer_tz}, memory::data_type::f32,
                memory::format_tag::ldigo);

auto user_enc_bidir_wei_iter_md = memory::desc({enc_bidir_weights_iter_tz},
        memory::data_type::f32, memory::format_tag::ldigo);

auto user_enc_bidir_bias_md = memory::desc({enc_bidir_bias_tz},
        memory::data_type::f32, memory::format_tag::ldgo);

auto user_enc_bidir_src_layer_memory
        = memory(user_enc_bidir_src_layer_md, cpu_engine, net_src.data());
auto user_enc_bidir_wei_layer_memory = memory(user_enc_bidir_wei_layer_md,
        cpu_engine, user_enc_bidir_wei_layer.data());
auto user_enc_bidir_wei_iter_memory = memory(user_enc_bidir_wei_iter_md,
        cpu_engine, user_enc_bidir_wei_iter.data());
auto user_enc_bidir_bias_memory = memory(
        user_enc_bidir_bias_md, cpu_engine, user_enc_bidir_bias.data());

Create memory descriptors for RNN data w/o specified layout

auto enc_bidir_src_layer_md = memory::desc({enc_bidir_src_layer_tz},
        memory::data_type::u8, memory::format_tag::any);

auto enc_bidir_wei_layer_md = memory::desc({enc_bidir_weights_layer_tz},
        memory::data_type::s8, memory::format_tag::any);

auto enc_bidir_wei_iter_md = memory::desc({enc_bidir_weights_iter_tz},
        memory::data_type::s8, memory::format_tag::any);

auto enc_bidir_dst_layer_md = memory::desc({enc_bidir_dst_layer_tz},
        memory::data_type::u8, memory::format_tag::any);

Create bidirectional RNN

Define RNN attributes that store quantization parameters

primitive_attr attr;
attr.set_rnn_data_qparams(data_scale, data_shift);
attr.set_rnn_weights_qparams(weights_scale_mask, weights_scales);

// check if int8 LSTM is supported
lstm_forward::primitive_desc enc_bidir_prim_desc;
try {
    enc_bidir_prim_desc = lstm_forward::primitive_desc(cpu_engine,
            prop_kind::forward_inference,
            rnn_direction::bidirectional_concat, enc_bidir_src_layer_md,
            memory::desc(), memory::desc(), enc_bidir_wei_layer_md,
            enc_bidir_wei_iter_md, user_enc_bidir_bias_md,
            enc_bidir_dst_layer_md, memory::desc(), memory::desc(), attr);
} catch (error &e) {
    if (e.status == dnnl_unimplemented)
        throw example_allows_unimplemented {
                "No int8 LSTM implementation is available for this "
                "platform.\n"
                "Please refer to the developer guide for details."};

    // on any other error just re-throw
    throw;
}

Create memory for input data and use reorders to quantize values to int8 NOTE: same attributes are used when creating RNN primitive and reorders

auto enc_bidir_src_layer_memory
        = memory(enc_bidir_prim_desc.src_layer_desc(), cpu_engine);
auto enc_bidir_src_layer_reorder_pd = reorder::primitive_desc(
        user_enc_bidir_src_layer_memory, enc_bidir_src_layer_memory, attr);
encoder_net.push_back(reorder(enc_bidir_src_layer_reorder_pd));
encoder_net_args.push_back(
        {{DNNL_ARG_FROM, user_enc_bidir_src_layer_memory},
                {DNNL_ARG_TO, enc_bidir_src_layer_memory}});

Encoder : add the bidirectional rnn primitive with related arguments into encoder_net

encoder_net.push_back(lstm_forward(enc_bidir_prim_desc));
encoder_net_args.push_back(
        {{DNNL_ARG_SRC_LAYER, enc_bidir_src_layer_memory},
                {DNNL_ARG_WEIGHTS_LAYER, enc_bidir_wei_layer_memory},
                {DNNL_ARG_WEIGHTS_ITER, enc_bidir_wei_iter_memory},
                {DNNL_ARG_BIAS, user_enc_bidir_bias_memory},
                {DNNL_ARG_DST_LAYER, enc_bidir_dst_layer_memory}});

Encoder: unidirectional layers

First unidirectinal layer scales 2 * feature_size output of bidirectional layer to feature_size output

std::vector<float> user_enc_uni_first_wei_layer(
        1 * 1 * 2 * feature_size * lstm_n_gates * feature_size, 0.3f);
std::vector<float> user_enc_uni_first_wei_iter(
        1 * 1 * feature_size * lstm_n_gates * feature_size, 0.2f);
std::vector<float> user_enc_uni_first_bias(
        1 * 1 * lstm_n_gates * feature_size, 1.0f);

Encoder : Create unidirection RNN for first cell

auto enc_uni_first_prim_desc = lstm_forward::primitive_desc(cpu_engine,
        prop_kind::forward_inference,
        rnn_direction::unidirectional_left2right, enc_bidir_dst_layer_md,
        memory::desc(), memory::desc(), enc_uni_first_wei_layer_md,
        enc_uni_first_wei_iter_md, user_enc_uni_first_bias_md,
        enc_uni_first_dst_layer_md, memory::desc(), memory::desc(), attr);

Encoder : add the first unidirectional rnn primitive with related arguments into encoder_net

encoder_net.push_back(lstm_forward(enc_uni_first_prim_desc));
encoder_net_args.push_back(
        {{DNNL_ARG_SRC_LAYER, enc_bidir_dst_layer_memory},
                {DNNL_ARG_WEIGHTS_LAYER, enc_uni_first_wei_layer_memory},
                {DNNL_ARG_WEIGHTS_ITER, enc_uni_first_wei_iter_memory},
                {DNNL_ARG_BIAS, user_enc_uni_first_bias_memory},
                {DNNL_ARG_DST_LAYER, enc_uni_first_dst_layer_memory}});

Encoder : Remaining unidirectional layers

std::vector<float> user_enc_uni_wei_layer((enc_unidir_n_layers - 1) * 1
                * feature_size * lstm_n_gates * feature_size,
        0.3f);
std::vector<float> user_enc_uni_wei_iter((enc_unidir_n_layers - 1) * 1
                * feature_size * lstm_n_gates * feature_size,
        0.2f);
std::vector<float> user_enc_uni_bias(
        (enc_unidir_n_layers - 1) * 1 * lstm_n_gates * feature_size, 1.0f);

Encoder : Create unidirection RNN cell

auto enc_uni_prim_desc = lstm_forward::primitive_desc(cpu_engine,
        prop_kind::forward_inference,
        rnn_direction::unidirectional_left2right,
        enc_uni_first_dst_layer_md, memory::desc(), memory::desc(),
        enc_uni_wei_layer_md, enc_uni_wei_iter_md, user_enc_uni_bias_md,
        enc_dst_layer_md, memory::desc(), memory::desc(), attr);

Encoder : add the unidirectional rnn primitive with related arguments into encoder_net

encoder_net.push_back(lstm_forward(enc_uni_prim_desc));
encoder_net_args.push_back(
        {{DNNL_ARG_SRC_LAYER, enc_uni_first_dst_layer_memory},
                {DNNL_ARG_WEIGHTS_LAYER, enc_uni_wei_layer_memory},
                {DNNL_ARG_WEIGHTS_ITER, enc_uni_wei_iter_memory},
                {DNNL_ARG_BIAS, user_enc_uni_bias_memory},
                {DNNL_ARG_DST_LAYER, enc_dst_layer_memory}});

Decoder with attention mechanism

Decoder : declare memory dimensions

std::vector<float> user_dec_wei_layer(
        dec_n_layers * 1 * feature_size * lstm_n_gates * feature_size,
        0.2f);
std::vector<float> user_dec_wei_iter(dec_n_layers * 1
                * (feature_size + feature_size) * lstm_n_gates
                * feature_size,
        0.3f);
std::vector<float> user_dec_bias(
        dec_n_layers * 1 * lstm_n_gates * feature_size, 1.0f);
std::vector<int8_t> user_weights_attention_src_layer(
        feature_size * feature_size, 1);
float weights_attention_scale = 127.;
std::vector<float> user_weights_annotation(
        feature_size * feature_size, 1.0f);
std::vector<float> user_weights_alignments(feature_size, 1.0f);
// Buffer to store decoder output for all iterations
std::vector<uint8_t> dec_dst(tgt_seq_length_max * batch * feature_size, 0);

memory::dims user_dec_wei_layer_dims
        = {dec_n_layers, 1, feature_size, lstm_n_gates, feature_size};
memory::dims user_dec_wei_iter_dims = {dec_n_layers, 1,
        feature_size + feature_size, lstm_n_gates, feature_size};
memory::dims user_dec_bias_dims
        = {dec_n_layers, 1, lstm_n_gates, feature_size};
memory::dims dec_src_layer_dims = {1, batch, feature_size};
memory::dims dec_dst_layer_dims = {1, batch, feature_size};
memory::dims dec_dst_iter_c_dims = {dec_n_layers, 1, batch, feature_size};

std::vector<float> dec_dst_iter(
        dec_n_layers * batch * 2 * feature_size, 1.0f);

memory::dims dec_dst_iter_dims
        = {dec_n_layers, 1, batch, feature_size + feature_size};
memory::dims dec_dst_iter_noctx_dims
        = {dec_n_layers, 1, batch, feature_size};

Decoder : create memory description Create memory descriptors for RNN data w/o specified layout

auto user_dec_wei_layer_md = memory::desc({user_dec_wei_layer_dims},
        memory::data_type::f32, memory::format_tag::ldigo);
auto user_dec_wei_iter_md = memory::desc({user_dec_wei_iter_dims},
        memory::data_type::f32, memory::format_tag::ldigo);
auto user_dec_bias_md = memory::desc({user_dec_bias_dims},
        memory::data_type::f32, memory::format_tag::ldgo);
auto dec_src_layer_md = memory::desc({dec_src_layer_dims},
        memory::data_type::u8, memory::format_tag::tnc);
auto dec_dst_layer_md = memory::desc({dec_dst_layer_dims},
        memory::data_type::u8, memory::format_tag::tnc);
auto dec_dst_iter_md = memory::desc({dec_dst_iter_dims},
        memory::data_type::f32, memory::format_tag::ldnc);
auto dec_dst_iter_c_md = memory::desc({dec_dst_iter_c_dims},
        memory::data_type::f32, memory::format_tag::ldnc);

Decoder : Create memory

auto user_dec_wei_layer_memory = memory(
        user_dec_wei_layer_md, cpu_engine, user_dec_wei_layer.data());
auto user_dec_wei_iter_memory = memory(
        user_dec_wei_iter_md, cpu_engine, user_dec_wei_iter.data());
auto user_dec_bias_memory
        = memory(user_dec_bias_md, cpu_engine, user_dec_bias.data());
auto dec_src_layer_memory = memory(dec_src_layer_md, cpu_engine);
auto dec_dst_layer_memory
        = memory(dec_dst_layer_md, cpu_engine, dec_dst.data());
auto dec_dst_iter_c_memory = memory(dec_dst_iter_c_md, cpu_engine);

Decoder : As mentioned above, we create a view without context out of the memory with context.

auto dec_dst_iter_memory
        = memory(dec_dst_iter_md, cpu_engine, dec_dst_iter.data());
auto dec_dst_iter_noctx_md = dec_dst_iter_md.submemory_desc(
        dec_dst_iter_noctx_dims, {0, 0, 0, 0, 0});

Decoder : Create memory for input data and use reorders to quantize values to int8

auto dec_wei_layer_memory
        = memory(dec_ctx_prim_desc.weights_layer_desc(), cpu_engine);
auto dec_wei_layer_reorder_pd = reorder::primitive_desc(
        user_dec_wei_layer_memory, dec_wei_layer_memory, attr);
reorder(dec_wei_layer_reorder_pd)
        .execute(s, user_dec_wei_layer_memory, dec_wei_layer_memory);

Execution

run encoder (1 stream)

for (size_t p = 0; p < encoder_net.size(); ++p)
    encoder_net.at(p).execute(s, encoder_net_args.at(p));

we compute the weighted annotations once before the decoder

compute_weighted_annotations(weighted_annotations.data(),
        src_seq_length_max, batch, feature_size,
        user_weights_annotation.data(),
        (float *)enc_dst_layer_memory.get_data_handle());

precompute compensation for s8u8s32 gemm in compute attention

compute_sum_of_rows(user_weights_attention_src_layer.data(),
        feature_size, feature_size, weights_attention_sum_rows.data());

We initialize src_layer to the embedding of the end of sequence character, which are assumed to be 0 here

memset(dec_src_layer_memory.get_data_handle(), 0,
        dec_src_layer_memory.get_desc().get_size());

From now on, src points to the output of the last iteration

Compute attention context vector into the first layer src_iter

compute_attention(src_att_iter_handle, src_seq_length_max, batch,
        feature_size, user_weights_attention_src_layer.data(),
        weights_attention_scale, weights_attention_sum_rows.data(),
        src_att_layer_handle, data_scale, data_shift,
        (uint8_t *)enc_bidir_dst_layer_memory.get_data_handle(),
        weighted_annotations.data(),
        user_weights_alignments.data());

copy the context vectors to all layers of src_iter

copy_context(
        src_att_iter_handle, dec_n_layers, batch, feature_size);

run the decoder iteration

for (size_t p = 0; p < decoder_net.size(); ++p)
    decoder_net.at(p).execute(s, decoder_net_args.at(p));

Move the handle on the src/dst layer to the next iteration

auto dst_layer_handle
        = (uint8_t *)dec_dst_layer_memory.get_data_handle();
dec_src_layer_memory.set_data_handle(dst_layer_handle);
dec_dst_layer_memory.set_data_handle(
        dst_layer_handle + batch * feature_size);

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RNN int8 inference example