Llama 3.1 8B · SwiGLU MLP · OpenModelAtlas

in: $x$ [B batch, T positions, 4096 d]
out: $\Delta_{\mathrm{mlp}}$ [B batch, T positions, 4096 d]
parameters: 176,160,768 · × 32 blocks = 5,637,144,576

Parameters

176,160,768 parameters per instance, across its learned components

Exact per-instance accounting
Component	Calculation	Parameters
Gate projection	$4{,}096 \times 14{,}336$	58,720,256
Up projection	$4{,}096 \times 14{,}336$	58,720,256
Down projection	$14{,}336 \times 4{,}096$	58,720,256
Per-instance total		176,160,768

MLP width, derived from the configuration

$4d=4\times 4{,}096=16{,}384$ mlp-width config
$\left\lfloor \tfrac{2}{3}\times 16{,}384\right\rfloor=10{,}922$ mlp-width
$\left\lfloor 1.3\times 10{,}922\right\rfloor=14{,}198$ config mlp-width
$1{,}024\times\left\lceil 14{,}198/1{,}024\right\rceil=14{,}336=d_{ff}$ config mlp-width

Across 32 independent blocks: $176{,}160{,}768 \times 32 = 5{,}637{,}144{,}576$ parameters.

Derived from the pinned catalogue dimensions and implementation. Checkpoint tensors have not been independently counted.

In numbers

Weights · one MLP

Llama 3.1 8B · 16-bit336 MiB

GELU, same width · 16-bit224 MiB

3 × 4,096 × 14,336 = 176,160,768 parameters per MLP × 2 bytes; × 32 blocks = 5,637,144,576.

A GELU MLP of the same width: two matrices, 117,440,512; at $4d$ , 134,217,728.

model.py 208–216 model.py 193–234 sku_list.py 19–248 generation.py 105–108

Codemodel.py 193–248 · sku_list.py 19, 231–248

model.py 193–206

class FeedForward(nn.Module):
    def __init__(
        self,
        dim: int,
        hidden_dim: int,
        multiple_of: int,
        ffn_dim_multiplier: Optional[float],
    ):
        super().__init__()
        hidden_dim = int(2 * hidden_dim / 3)
        # custom dim factor multiplier
        if ffn_dim_multiplier is not None:
            hidden_dim = int(ffn_dim_multiplier * hidden_dim)
        hidden_dim = multiple_of * ((hidden_dim + multiple_of - 1) // multiple_of)

model.py 229–234

        self.feed_forward = FeedForward(
            dim=args.dim,
            hidden_dim=4 * args.dim,
            multiple_of=args.multiple_of,
            ffn_dim_multiplier=args.ffn_dim_multiplier,
        )

model.py 208–219

        self.w1 = ColumnParallelLinear(
            dim, hidden_dim, bias=False, gather_output=False, init_method=lambda x: x
        )
        self.w2 = RowParallelLinear(
            hidden_dim, dim, bias=False, input_is_parallel=True, init_method=lambda x: x
        )
        self.w3 = ColumnParallelLinear(
            dim, hidden_dim, bias=False, gather_output=False, init_method=lambda x: x
        )

    def forward(self, x):
        return self.w2(F.silu(self.w1(x)) * self.w3(x))

model.py 236–248

        self.attention_norm = RMSNorm(args.dim, eps=args.norm_eps)
        self.ffn_norm = RMSNorm(args.dim, eps=args.norm_eps)

    def forward(
        self,
        x: torch.Tensor,
        start_pos: int,
        freqs_cis: torch.Tensor,
        mask: Optional[torch.Tensor],
    ):
        h = x + self.attention(self.attention_norm(x), start_pos, freqs_cis, mask)
        out = h + self.feed_forward(self.ffn_norm(h))
        return out

sku_list.py 19

LLAMA3_VOCAB_SIZE = 128256

sku_list.py 231–248

        Model(
            core_model_id=CoreModelId.llama3_1_8b,
            description="Llama 3.1 8b model",
            huggingface_repo="meta-llama/Llama-3.1-8B",
            arch_args={
                "dim": 4096,
                "n_layers": 32,
                "n_heads": 32,
                "n_kv_heads": 8,
                "vocab_size": LLAMA3_VOCAB_SIZE,
                "ffn_dim_multiplier": 1.3,
                "multiple_of": 1024,
                "norm_eps": 1e-05,
                "rope_theta": 500000.0,
                "use_scaled_rope": True,
            },
            pth_file_count=1,
        ),

Sources4

Based on Meta’s pinned catalogue and reference implementation. Direct checkpoint configuration and tokenizer assets remain unverified.

Direct evidence

Meta's Llama 3.1 8B base catalogue entry supplies dimensions, head counts, the vocabulary (LLAMA3_VOCAB_SIZE, line 19), MLP rounding, epsilon, rope_theta and use_scaled_rope: True.

config · meta-llama/llama-models / models/sku_list.py
Pinned revision 0e0b8c519242 ↗ · lines 19–248

Read code excerpt

LLAMA3_VOCAB_SIZE = 128256

… lines 20–230 omitted …

        Model(
            core_model_id=CoreModelId.llama3_1_8b,
            description="Llama 3.1 8b model",
            huggingface_repo="meta-llama/Llama-3.1-8B",
            arch_args={
                "dim": 4096,
                "n_layers": 32,
                "n_heads": 32,
                "n_kv_heads": 8,
                "vocab_size": LLAMA3_VOCAB_SIZE,
                "ffn_dim_multiplier": 1.3,
                "multiple_of": 1024,
                "norm_eps": 1e-05,
                "rope_theta": 500000.0,
                "use_scaled_rope": True,
            },
            pth_file_count=1,
        ),

Direct evidence

The block passes four times model width; FeedForward truncates, applies the configured multiplier and rounds to the configured multiple.

mlp-width · meta-llama/llama3 / llama/model.py
Pinned revision a0940f9cf706 ↗ · lines 193–234

Read code excerpt

class FeedForward(nn.Module):
    def __init__(
        self,
        dim: int,
        hidden_dim: int,
        multiple_of: int,
        ffn_dim_multiplier: Optional[float],
    ):
        super().__init__()
        hidden_dim = int(2 * hidden_dim / 3)
        # custom dim factor multiplier
        if ffn_dim_multiplier is not None:
            hidden_dim = int(ffn_dim_multiplier * hidden_dim)
        hidden_dim = multiple_of * ((hidden_dim + multiple_of - 1) // multiple_of)

… lines 207–228 omitted …

        self.feed_forward = FeedForward(
            dim=args.dim,
            hidden_dim=4 * args.dim,
            multiple_of=args.multiple_of,
            ffn_dim_multiplier=args.ffn_dim_multiplier,
        )

Direct evidence

The MLP owns three bias-free projections. Its forward expression applies SiLU to w1(x), multiplies w3(x) element-wise and projects through w2.

mlp · meta-llama/llama3 / llama/model.py
Pinned revision a0940f9cf706 ↗ · lines 208–219

Read code excerpt

        self.w1 = ColumnParallelLinear(
            dim, hidden_dim, bias=False, gather_output=False, init_method=lambda x: x
        )
        self.w2 = RowParallelLinear(
            hidden_dim, dim, bias=False, input_is_parallel=True, init_method=lambda x: x
        )
        self.w3 = ColumnParallelLinear(
            dim, hidden_dim, bias=False, gather_output=False, init_method=lambda x: x
        )

    def forward(self, x):
        return self.w2(F.silu(self.w1(x)) * self.w3(x))

Direct evidence

Attention receives attention_norm(x) and its update is added to x; the MLP receives ffn_norm(h) and its update is added to h.

handoff · meta-llama/llama3 / llama/model.py
Pinned revision a0940f9cf706 ↗ · lines 236–248

Read code excerpt

        self.attention_norm = RMSNorm(args.dim, eps=args.norm_eps)
        self.ffn_norm = RMSNorm(args.dim, eps=args.norm_eps)

    def forward(
        self,
        x: torch.Tensor,
        start_pos: int,
        freqs_cis: torch.Tensor,
        mask: Optional[torch.Tensor],
    ):
        h = x + self.attention(self.attention_norm(x), start_pos, freqs_cis, mask)
        out = h + self.feed_forward(self.ffn_norm(h))
        return out