ctransformers/models/llms/gpt2.cc

#include "llm.h"

// https://github.com/ggerganov/ggml/blob/master/examples/gpt-2/main.cpp

// default hparams (GPT-2 117M)
struct gpt2_hparams {
  int32_t n_vocab = 50257;
  int32_t n_ctx = 1024;
  int32_t n_embd = 768;
  int32_t n_head = 12;
  int32_t n_layer = 12;
  int32_t ftype = 1;
};

struct gpt2_layer {
  // normalization
  struct ggml_tensor *ln_1_g;
  struct ggml_tensor *ln_1_b;

  struct ggml_tensor *ln_2_g;
  struct ggml_tensor *ln_2_b;

  // attention
  struct ggml_tensor *c_attn_attn_w;
  struct ggml_tensor *c_attn_attn_b;

  struct ggml_tensor *c_attn_proj_w;
  struct ggml_tensor *c_attn_proj_b;

  // mlp
  struct ggml_tensor *c_mlp_fc_w;
  struct ggml_tensor *c_mlp_fc_b;

  struct ggml_tensor *c_mlp_proj_w;
  struct ggml_tensor *c_mlp_proj_b;
};

struct gpt2_model {
  gpt2_hparams hparams;

  // normalization
  struct ggml_tensor *ln_f_g;
  struct ggml_tensor *ln_f_b;

  struct ggml_tensor *wte;      // position embedding
  struct ggml_tensor *wpe;      //    token embedding
  struct ggml_tensor *lm_head;  // language model head

  std::vector<gpt2_layer> layers;

  // key + value memory
  struct ggml_tensor *memory_k;
  struct ggml_tensor *memory_v;

  //
  struct ggml_context *ctx;
  std::map<std::string, struct ggml_tensor *> tensors;
};

// load the model's weights from a file
bool gpt2_model_load(const std::string &fname, gpt2_model &model,
                     gpt_vocab &vocab) {
  auto fin = std::ifstream(fname, std::ios::binary);
  if (!fin) {
    fprintf(stderr, "%s: failed to open '%s'\n", __func__, fname.c_str());
    return false;
  }

  // verify magic
  {
    uint32_t magic;
    fin.read((char *)&magic, sizeof(magic));
    if (magic != 0x67676d6c) {
      fprintf(stderr, "%s: invalid model file '%s' (bad magic)\n", __func__,
              fname.c_str());
      return false;
    }
  }

  // load hparams
  {
    auto &hparams = model.hparams;

    fin.read((char *)&hparams.n_vocab, sizeof(hparams.n_vocab));
    fin.read((char *)&hparams.n_ctx, sizeof(hparams.n_ctx));
    fin.read((char *)&hparams.n_embd, sizeof(hparams.n_embd));
    fin.read((char *)&hparams.n_head, sizeof(hparams.n_head));
    fin.read((char *)&hparams.n_layer, sizeof(hparams.n_layer));
    fin.read((char *)&hparams.ftype, sizeof(hparams.ftype));

    const int32_t qntvr = hparams.ftype / GGML_QNT_VERSION_FACTOR;

    hparams.ftype %= GGML_QNT_VERSION_FACTOR;
  }

  // load vocab
  {
    int32_t n_vocab = 0;
    fin.read((char *)&n_vocab, sizeof(n_vocab));

    if (n_vocab != model.hparams.n_vocab) {
      fprintf(stderr, "%s: invalid model file '%s' (bad vocab size %d != %d)\n",
              __func__, fname.c_str(), n_vocab, model.hparams.n_vocab);
      return false;
    }

    std::string word;
    std::vector<char> buf(128);

    for (int i = 0; i < n_vocab; i++) {
      uint32_t len;
      fin.read((char *)&len, sizeof(len));

      buf.resize(len);
      fin.read((char *)buf.data(), len);
      word.assign(buf.data(), len);

      vocab.token_to_id[word] = i;
      vocab.id_to_token[i] = word;
    }
  }

  // for the big tensors, we have the option to store the data in 16-bit floats
  // or quantized in order to save memory and also to speed up the computation
  ggml_type wtype = ggml_ftype_to_ggml_type((ggml_ftype)(model.hparams.ftype));
  if (wtype == GGML_TYPE_COUNT) {
    fprintf(stderr, "%s: invalid model file '%s' (bad ftype value %d)\n",
            __func__, fname.c_str(), model.hparams.ftype);
    return false;
  }

  auto &ctx = model.ctx;

  size_t ctx_size = 0;

  {
    const auto &hparams = model.hparams;

    const int n_embd = hparams.n_embd;
    const int n_layer = hparams.n_layer;
    const int n_ctx = hparams.n_ctx;
    const int n_vocab = hparams.n_vocab;

    ctx_size += n_embd * ggml_type_sizef(GGML_TYPE_F32);  // ln_f_g
    ctx_size += n_embd * ggml_type_sizef(GGML_TYPE_F32);  // ln_f_b

    ctx_size += n_vocab * n_embd * ggml_type_sizef(wtype);        // wte
    ctx_size += n_ctx * n_embd * ggml_type_sizef(GGML_TYPE_F32);  // wpe
    ctx_size += n_vocab * n_embd * ggml_type_sizef(wtype);        // lm_head

    ctx_size += n_layer * (n_embd * ggml_type_sizef(GGML_TYPE_F32));  // ln_1_g
    ctx_size += n_layer * (n_embd * ggml_type_sizef(GGML_TYPE_F32));  // ln_1_b

    ctx_size += n_layer * (n_embd * ggml_type_sizef(GGML_TYPE_F32));  // ln_2_g
    ctx_size += n_layer * (n_embd * ggml_type_sizef(GGML_TYPE_F32));  // ln_2_b

    ctx_size += n_layer * (3 * n_embd * n_embd *
                           ggml_type_sizef(wtype));  // c_attn_attn_w
    ctx_size += n_layer *
                (3 * n_embd * ggml_type_sizef(GGML_TYPE_F32));  // c_attn_attn_b

    ctx_size +=
        n_layer * (n_embd * n_embd * ggml_type_sizef(wtype));  // c_attn_proj_w
    ctx_size +=
        n_layer * (n_embd * ggml_type_sizef(GGML_TYPE_F32));  // c_attn_proj_b

    ctx_size +=
        n_layer * (4 * n_embd * n_embd * ggml_type_sizef(wtype));  // c_mlp_fc_w
    ctx_size +=
        n_layer * (4 * n_embd * ggml_type_sizef(GGML_TYPE_F32));  // c_mlp_fc_b

    ctx_size += n_layer *
                (4 * n_embd * n_embd * ggml_type_sizef(wtype));  // c_mlp_proj_w
    ctx_size +=
        n_layer * (n_embd * ggml_type_sizef(GGML_TYPE_F32));  // c_mlp_proj_b

    ctx_size +=
        n_ctx * n_layer * n_embd * ggml_type_sizef(GGML_TYPE_F32);  // memory_k
    ctx_size +=
        n_ctx * n_layer * n_embd * ggml_type_sizef(GGML_TYPE_F32);  // memory_v

    ctx_size += (6 + 12 * n_layer) * 512;  // object overhead
  }

  // create the ggml context
  {
    struct ggml_init_params params = {
        /*.mem_size   =*/ctx_size,
        /*.mem_buffer =*/NULL,
        /*.no_alloc   =*/false,
    };

    model.ctx = ggml_init(params);
    if (!model.ctx) {
      fprintf(stderr, "%s: ggml_init() failed\n", __func__);
      return false;
    }
  }

  // prepare memory for the weights
  {
    const auto &hparams = model.hparams;

    const int n_embd = hparams.n_embd;
    const int n_layer = hparams.n_layer;
    const int n_ctx = hparams.n_ctx;
    const int n_vocab = hparams.n_vocab;

    model.layers.resize(n_layer);

    model.ln_f_g = ggml_new_tensor_1d(ctx, GGML_TYPE_F32, n_embd);
    model.ln_f_b = ggml_new_tensor_1d(ctx, GGML_TYPE_F32, n_embd);

    model.wte = ggml_new_tensor_2d(ctx, wtype, n_embd, n_vocab);
    model.wpe = ggml_new_tensor_2d(ctx, GGML_TYPE_F32, n_embd, n_ctx);
    model.lm_head = ggml_new_tensor_2d(ctx, wtype, n_embd, n_vocab);

    // map by name
    model.tensors["model/ln_f/g"] = model.ln_f_g;
    model.tensors["model/ln_f/b"] = model.ln_f_b;

    model.tensors["model/wte"] = model.wte;
    model.tensors["model/wpe"] = model.wpe;
    model.tensors["model/lm_head"] = model.lm_head;

    for (int i = 0; i < n_layer; ++i) {
      auto &layer = model.layers[i];

      layer.ln_1_g = ggml_new_tensor_1d(ctx, GGML_TYPE_F32, n_embd);
      layer.ln_1_b = ggml_new_tensor_1d(ctx, GGML_TYPE_F32, n_embd);

      layer.ln_2_g = ggml_new_tensor_1d(ctx, GGML_TYPE_F32, n_embd);
      layer.ln_2_b = ggml_new_tensor_1d(ctx, GGML_TYPE_F32, n_embd);

      layer.c_attn_attn_w = ggml_new_tensor_2d(ctx, wtype, n_embd, 3 * n_embd);
      layer.c_attn_attn_b = ggml_new_tensor_1d(ctx, GGML_TYPE_F32, 3 * n_embd);

      layer.c_attn_proj_w = ggml_new_tensor_2d(ctx, wtype, n_embd, n_embd);
      layer.c_attn_proj_b = ggml_new_tensor_1d(ctx, GGML_TYPE_F32, n_embd);

      layer.c_mlp_fc_w = ggml_new_tensor_2d(ctx, wtype, n_embd, 4 * n_embd);
      layer.c_mlp_fc_b = ggml_new_tensor_1d(ctx, GGML_TYPE_F32, 4 * n_embd);

      layer.c_mlp_proj_w = ggml_new_tensor_2d(ctx, wtype, 4 * n_embd, n_embd);
      layer.c_mlp_proj_b = ggml_new_tensor_1d(ctx, GGML_TYPE_F32, n_embd);

      // map by name
      model.tensors["model/h" + std::to_string(i) + "/ln_1/g"] = layer.ln_1_g;
      model.tensors["model/h" + std::to_string(i) + "/ln_1/b"] = layer.ln_1_b;

      model.tensors["model/h" + std::to_string(i) + "/ln_2/g"] = layer.ln_2_g;
      model.tensors["model/h" + std::to_string(i) + "/ln_2/b"] = layer.ln_2_b;

      model.tensors["model/h" + std::to_string(i) + "/attn/c_attn/w"] =
          layer.c_attn_attn_w;
      model.tensors["model/h" + std::to_string(i) + "/attn/c_attn/b"] =
          layer.c_attn_attn_b;

      model.tensors["model/h" + std::to_string(i) + "/attn/c_proj/w"] =
          layer.c_attn_proj_w;
      model.tensors["model/h" + std::to_string(i) + "/attn/c_proj/b"] =
          layer.c_attn_proj_b;

      model.tensors["model/h" + std::to_string(i) + "/mlp/c_fc/w"] =
          layer.c_mlp_fc_w;
      model.tensors["model/h" + std::to_string(i) + "/mlp/c_fc/b"] =
          layer.c_mlp_fc_b;

      model.tensors["model/h" + std::to_string(i) + "/mlp/c_proj/w"] =
          layer.c_mlp_proj_w;
      model.tensors["model/h" + std::to_string(i) + "/mlp/c_proj/b"] =
          layer.c_mlp_proj_b;
    }
  }

  // key + value memory
  {
    const auto &hparams = model.hparams;

    const int n_embd = hparams.n_embd;
    const int n_layer = hparams.n_layer;
    const int n_ctx = hparams.n_ctx;

    const int n_mem = n_layer * n_ctx;
    const int n_elements = n_embd * n_mem;

    model.memory_k = ggml_new_tensor_1d(ctx, GGML_TYPE_F32, n_elements);
    model.memory_v = ggml_new_tensor_1d(ctx, GGML_TYPE_F32, n_elements);

    const size_t memory_size =
        ggml_nbytes(model.memory_k) + ggml_nbytes(model.memory_v);
  }

  // load weights
  {
    size_t total_size = 0;

    bool has_lm_head = false;

    while (true) {
      int32_t n_dims;
      int32_t length;
      int32_t ttype;

      fin.read(reinterpret_cast<char *>(&n_dims), sizeof(n_dims));
      fin.read(reinterpret_cast<char *>(&length), sizeof(length));
      fin.read(reinterpret_cast<char *>(&ttype), sizeof(ttype));

      if (fin.eof()) {
        break;
      }

      int32_t nelements = 1;
      int32_t ne[2] = {1, 1};
      for (int i = 0; i < n_dims; ++i) {
        fin.read(reinterpret_cast<char *>(&ne[i]), sizeof(ne[i]));
        nelements *= ne[i];
      }

      std::string name(length, 0);
      fin.read(&name[0], length);

      if (model.tensors.find(name.data()) == model.tensors.end()) {
        fprintf(stderr, "%s: unknown tensor '%s' in model file\n", __func__,
                name.data());
        return false;
      }

      auto tensor = model.tensors[name.data()];
      if (ggml_nelements(tensor) != nelements) {
        fprintf(stderr, "%s: tensor '%s' has wrong size in model file\n",
                __func__, name.data());
        return false;
      }

      if (tensor->ne[0] != ne[0] || tensor->ne[1] != ne[1]) {
        fprintf(stderr,
                "%s: tensor '%s' has wrong shape in model file: got [%d, %d], "
                "expected [%d, %d]\n",
                __func__, name.data(), (int)tensor->ne[0], (int)tensor->ne[1],
                ne[0], ne[1]);
        return false;
      }

      // for debugging
      if (0) {
        printf("%24s - [%5d, %5d], type = %6s, %6.2f MB, %9zu bytes\n",
               name.data(), ne[0], ne[1], ggml_type_name(ggml_type(ttype)),
               ggml_nbytes(tensor) / 1024.0 / 1024.0, ggml_nbytes(tensor));
      }

      const size_t bpe = ggml_type_size(ggml_type(ttype));

      if ((nelements * bpe) / ggml_blck_size(tensor->type) !=
          ggml_nbytes(tensor)) {
        fprintf(stderr,
                "%s: tensor '%s' has wrong size in model file: got %zu, "
                "expected %zu\n",
                __func__, name.data(), ggml_nbytes(tensor), nelements * bpe);
        return false;
      }

      fin.read(reinterpret_cast<char *>(tensor->data), ggml_nbytes(tensor));

      // GPT-2 models share the WTE tensor as the LM head
      if (name == "model/wte" && has_lm_head == false) {
        memcpy(model.lm_head->data, tensor->data, ggml_nbytes(tensor));
      }

      if (name == "model/lm_head") {
        has_lm_head = true;
      }

      total_size += ggml_nbytes(tensor);
    }
  }

  fin.close();

  return true;
}

// evaluate the transformer
//
//   - model:     the model
//   - n_threads: number of threads to use
//   - n_past:    the context size so far
//   - embd_inp:  the embeddings of the tokens in the context
//   - embd_w:    the predicted logits for the next token
//
bool gpt2_eval(const gpt2_model &model, const int n_threads, const int n_past,
               const std::vector<gpt_vocab::id> &embd_inp,
               std::vector<float> &embd_w, size_t &mem_per_token) {
  const int N = embd_inp.size();

  const auto &hparams = model.hparams;

  const int n_embd = hparams.n_embd;
  const int n_layer = hparams.n_layer;
  const int n_ctx = hparams.n_ctx;
  const int n_head = hparams.n_head;
  const int n_vocab = hparams.n_vocab;

  static size_t buf_size = 256u * 1024 * 1024;
  static void *buf = malloc(buf_size);

  if (mem_per_token > 0 && mem_per_token * N > buf_size) {
    const size_t buf_size_new =
        1.1 *
        (mem_per_token * N);  // add 10% to account for ggml object overhead
    // printf("\n%s: reallocating buffer from %zu to %zu bytes\n", __func__,
    // buf_size, buf_size_new);

    // reallocate
    buf_size = buf_size_new;
    buf = realloc(buf, buf_size);
    if (buf == nullptr) {
      fprintf(stderr, "%s: failed to allocate %zu bytes\n", __func__, buf_size);
      return false;
    }
  }

  struct ggml_init_params params = {
      /*.mem_size   =*/buf_size,
      /*.mem_buffer =*/buf,
      /*.no_alloc   =*/false,
  };

  struct ggml_context *ctx0 = ggml_init(params);
  struct ggml_cgraph gf = {};
  gf.n_threads = n_threads;

  struct ggml_tensor *embd = ggml_new_tensor_1d(ctx0, GGML_TYPE_I32, N);
  memcpy(embd->data, embd_inp.data(), N * ggml_element_size(embd));

  struct ggml_tensor *position = ggml_new_tensor_1d(ctx0, GGML_TYPE_I32, N);
  for (int i = 0; i < N; ++i) {
    ((int32_t *)position->data)[i] = n_past + i;
  }

  // wte + wpe
  struct ggml_tensor *inpL =
      ggml_add(ctx0, ggml_get_rows(ctx0, model.wte, embd),
               ggml_get_rows(ctx0, model.wpe, position));

  for (int il = 0; il < n_layer; ++il) {
    struct ggml_tensor *cur;

    // norm
    {
      // [ 768, N]
      cur = ggml_norm(ctx0, inpL);

      // cur = ln_1_g*cur + ln_1_b
      // [ 768, N]
      cur = ggml_add(
          ctx0,
          ggml_mul(ctx0, ggml_repeat(ctx0, model.layers[il].ln_1_g, cur), cur),
          ggml_repeat(ctx0, model.layers[il].ln_1_b, cur));
    }

    // attn
    // [2304, 768] - model.layers[il].c_attn_attn_w
    // [2304,   1] - model.layers[il].c_attn_attn_b
    // [ 768,   N] - cur (in)
    // [2304,   N] - cur (out)
    //
    // cur = attn_w*cur + attn_b
    // [2304, N]
    {
      cur = ggml_mul_mat(ctx0, model.layers[il].c_attn_attn_w, cur);

      cur = ggml_add(
          ctx0, ggml_repeat(ctx0, model.layers[il].c_attn_attn_b, cur), cur);
    }

    // self-attention
    {
      struct ggml_tensor *Qcur = ggml_view_2d(ctx0, cur, n_embd, N, cur->nb[1],
                                              0 * sizeof(float) * n_embd);
      struct ggml_tensor *Kcur = ggml_view_2d(ctx0, cur, n_embd, N, cur->nb[1],
                                              1 * sizeof(float) * n_embd);
      struct ggml_tensor *Vcur = ggml_view_2d(ctx0, cur, n_embd, N, cur->nb[1],
                                              2 * sizeof(float) * n_embd);

      // store key and value to memory
      if (N >= 1) {
        struct ggml_tensor *k =
            ggml_view_1d(ctx0, model.memory_k, N * n_embd,
                         (ggml_element_size(model.memory_k) * n_embd) *
                             (il * n_ctx + n_past));
        struct ggml_tensor *v =
            ggml_view_1d(ctx0, model.memory_v, N * n_embd,
                         (ggml_element_size(model.memory_v) * n_embd) *
                             (il * n_ctx + n_past));

        ggml_build_forward_expand(&gf, ggml_cpy(ctx0, Kcur, k));
        ggml_build_forward_expand(&gf, ggml_cpy(ctx0, Vcur, v));
      }

      // Q = Qcur.contiguous().view(n_embd/n_head, n_head, N).permute(0, 2, 1,
      // 3) [64, N, 12]
      struct ggml_tensor *Q =
          ggml_permute(ctx0,
                       ggml_cpy(ctx0, Qcur,
                                ggml_new_tensor_3d(ctx0, GGML_TYPE_F32,
                                                   n_embd / n_head, n_head, N)),
                       0, 2, 1, 3);

      // K = Kmem.view(n_embd/n_head, n_head, n_past + N).permute(0, 2, 1, 3)
      // [64, n_past + N, 12]
      struct ggml_tensor *K = ggml_permute(
          ctx0,
          ggml_reshape_3d(
              ctx0,
              ggml_view_1d(
                  ctx0, model.memory_k, (n_past + N) * n_embd,
                  il * n_ctx * ggml_element_size(model.memory_k) * n_embd),
              n_embd / n_head, n_head, n_past + N),
          0, 2, 1, 3);

      // GG: flash attention
      // struct ggml_tensor * V =
      //    ggml_cpy(ctx0,
      //            ggml_permute(ctx0,
      //                ggml_reshape_3d(ctx0,
      //                    ggml_view_1d(ctx0, model.memory_v, (n_past +
      //                    N)*n_embd,
      //                    il*n_ctx*ggml_element_size(model.memory_v)*n_embd),
      //                    n_embd/n_head, n_head, n_past + N),
      //                1, 2, 0, 3),
      //            ggml_new_tensor_3d(ctx0, GGML_TYPE_F32, n_past + N,
      //            n_embd/n_head, n_head));

      // struct ggml_tensor * KQV = ggml_flash_attn(ctx0, Q, K, V, true);

      // K * Q
      // [n_past + N, N, 12]
      struct ggml_tensor *KQ = ggml_mul_mat(ctx0, K, Q);

      // KQ_scaled = KQ / sqrt(n_embd/n_head)
      // [n_past + N, N, 12]
      struct ggml_tensor *KQ_scaled = ggml_scale_inplace(
          ctx0, KQ, ggml_new_f32(ctx0, 1.0f / sqrt(float(n_embd) / n_head)));

      // KQ_masked = mask_past(KQ_scaled)
      // [n_past + N, N, 12]
      struct ggml_tensor *KQ_masked =
          ggml_diag_mask_inf_inplace(ctx0, KQ_scaled, n_past);

      // KQ = soft_max(KQ_masked)
      // [n_past + N, N, 12]
      struct ggml_tensor *KQ_soft_max = ggml_soft_max_inplace(ctx0, KQ_masked);

      // V_trans = Vmem.view(n_embd/n_head, n_head, n_past + N).permute(1, 2, 0,
      // 3).contiguous() [n_past + N, 64, 12]
      struct ggml_tensor *V_trans = ggml_cpy(
          ctx0,
          ggml_permute(
              ctx0,
              ggml_reshape_3d(
                  ctx0,
                  ggml_view_1d(
                      ctx0, model.memory_v, (n_past + N) * n_embd,
                      il * n_ctx * ggml_element_size(model.memory_v) * n_embd),
                  n_embd / n_head, n_head, n_past + N),
              1, 2, 0, 3),
          ggml_new_tensor_3d(ctx0, model.memory_v->type, n_past + N,
                             n_embd / n_head, n_head));

      // KQV = transpose(V) * KQ_soft_max
      // [64, N, 12]
      struct ggml_tensor *KQV = ggml_mul_mat(ctx0, V_trans, KQ_soft_max);

      // KQV_merged = KQV.permute(0, 2, 1, 3)
      // [64, 12, N]
      struct ggml_tensor *KQV_merged = ggml_permute(ctx0, KQV, 0, 2, 1, 3);

      // cur = KQV_merged.contiguous().view(n_embd, N)
      // [768, N]
      cur = ggml_cpy(ctx0, KQV_merged,
                     ggml_new_tensor_2d(ctx0, GGML_TYPE_F32, n_embd, N));
    }

    // projection
    // [ 768, 768] - model.layers[il].c_attn_proj_w
    // [ 768,   1] - model.layers[il].c_attn_proj_b
    // [ 768,   N] - cur (in)
    // [ 768,   N] - cur (out)
    //
    // cur = proj_w*cur + proj_b
    // [768, N]
    {
      cur = ggml_mul_mat(ctx0, model.layers[il].c_attn_proj_w, cur);

      cur = ggml_add(
          ctx0, ggml_repeat(ctx0, model.layers[il].c_attn_proj_b, cur), cur);
    }

    // add the input
    cur = ggml_add(ctx0, cur, inpL);

    struct ggml_tensor *inpFF = cur;

    // feed-forward network
    {
      // norm
      {
        cur = ggml_norm(ctx0, inpFF);

        // cur = ln_2_g*cur + ln_2_b
        // [ 768, N]
        cur = ggml_add(
            ctx0,
            ggml_mul(ctx0, ggml_repeat(ctx0, model.layers[il].ln_2_g, cur),
                     cur),
            ggml_repeat(ctx0, model.layers[il].ln_2_b, cur));
      }

      // fully connected
      // [3072, 768] - model.layers[il].c_mlp_fc_w
      // [3072,   1] - model.layers[il].c_mlp_fc_b
      // [ 768,   N] - cur (in)
      // [3072,   N] - cur (out)
      //
      // cur = fc_w*cur + fc_b
      // [3072, N]
      cur = ggml_mul_mat(ctx0, model.layers[il].c_mlp_fc_w, cur);

      cur = ggml_add(ctx0, ggml_repeat(ctx0, model.layers[il].c_mlp_fc_b, cur),
                     cur);

      // GELU activation
      // [3072, N]
      cur = ggml_gelu(ctx0, cur);

      // projection
      // [ 768, 3072] - model.layers[il].c_mlp_proj_w
      // [ 768,    1] - model.layers[il].c_mlp_proj_b
      // [3072,    N] - cur (in)
      // [ 768,    N] - cur (out)
      //
      // cur = proj_w*cur + proj_b
      // [768, N]
      cur = ggml_mul_mat(ctx0, model.layers[il].c_mlp_proj_w, cur);

      cur = ggml_add(
          ctx0, ggml_repeat(ctx0, model.layers[il].c_mlp_proj_b, cur), cur);
    }

    // input for next layer
    inpL = ggml_add(ctx0, cur, inpFF);
  }

  // norm
  {
    // [ 768, N]
    inpL = ggml_norm(ctx0, inpL);

    // inpL = ln_f_g*inpL + ln_f_b
    // [ 768, N]
    inpL = ggml_add(ctx0,
                    ggml_mul(ctx0, ggml_repeat(ctx0, model.ln_f_g, inpL), inpL),
                    ggml_repeat(ctx0, model.ln_f_b, inpL));
  }

  // inpL = WTE * inpL
  // [ 768, 50257] - model.lm_head
  // [ 768, N]     - inpL
  inpL = ggml_mul_mat(ctx0, model.lm_head, inpL);

  // logits -> probs
  // inpL = ggml_soft_max_inplace(ctx0, inpL);

  // run the computation
  ggml_build_forward_expand(&gf, inpL);
  ggml_graph_compute(ctx0, &gf);

  // if (n_past%100 == 0) {
  //    ggml_graph_print   (&gf);
  //    ggml_graph_dump_dot(&gf, NULL, "gpt-2.dot");
  //}

  // embd_w.resize(n_vocab*N);
  // memcpy(embd_w.data(), ggml_get_data(inpL), sizeof(float)*n_vocab*N);

  // return result just for the last token
  embd_w.resize(n_vocab);
  memcpy(embd_w.data(), (float *)ggml_get_data(inpL) + (n_vocab * (N - 1)),
         sizeof(float) * n_vocab);

  if (mem_per_token == 0) {
    mem_per_token = ggml_used_mem(ctx0) / N;
  }
  // printf("used_mem = %zu\n", ggml_used_mem(ctx0));

  ggml_free(ctx0);

  return true;
}

REGISTER_LLM(gpt2);