DeepSeek V4.1

class Transformer(nn.Module):
    """DeepSeek-V4.1: embed -> expand to hc_mult copies -> blocks -> collapse -> logits. Building
    this sets the globals at the top of the file. The tokenizer only feeds the engram token map."""

    def __init__(self, args: ModelArgs, tokenizer=None):
        global world_size, rank, default_dtype
        world_size = dist.get_world_size() if dist.is_initialized() else 1
        rank = dist.get_rank() if dist.is_initialized() else 0
        default_dtype = torch.float8_e4m3fn if args.dtype == "fp8" else torch.bfloat16
        super().__init__()
        self.max_seq_len = args.max_seq_len
        self.temperature = args.temperature
        self.norm_eps = args.norm_eps
        self.hc_eps = args.hc_eps
        self.engram_layout = EngramLayout.from_args(args)
        self.engram_hash = (
            NgramHashState(args, self.engram_layout, tokenizer) if self.engram_layout is not None else None
        )
        self.embed = ParallelEmbedding(args.vocab_size, args.dim)
        self.layers = torch.nn.ModuleList()
        for layer_id in range(args.n_layers):
            self.layers.append(Block(layer_id, args, self.engram_layout))
        self.norm = RMSNorm(args.dim, self.norm_eps)
        self.head = ParallelHead(args.vocab_size, args.dim, self.norm_eps, self.hc_eps)
        self.mtp = torch.nn.ModuleList()
        self.target_layer_ids = args.dspark_target_layer_ids
        if args.dspark_block_size:
            for layer_id in range(args.n_mtp_layers):
                self.mtp.append(DSparkBlock(args.n_layers + layer_id, args))
                self.mtp[-1].embed = self.embed
                self.mtp[-1].head = self.head
        self.hc_mult = args.hc_mult
        self.vision = None
        if args.vision_enabled:
            self.vision = ViT(args)
            self.aligner = Aligner(args)
            # learned embeddings for the image span delimiters
            self.image_start = nn.Parameter(torch.empty(args.dim))
            self.image_end = nn.Parameter(torch.empty(args.dim))
            self.image_newline = nn.Parameter(torch.empty(args.dim))

    @torch.inference_mode()
    def forward(
        self, input_ids: torch.Tensor, start_pos: int = 0, images=None, token_types: torch.Tensor | None = None
    ):
        """input_ids: [b, s], every entry a real token id -- generate.py only ever passes positions it
        has already filled, so the padding it uses internally never reaches here. token_types /
        images carry the VL inputs built by image_processor.prepare_vl_inputs; image spans must lie
        inside the first (start_pos 0) chunk."""
        image_mask = None if token_types is None else token_types >= 0  # TEXT is -1
        # image tokens take no part in an n-gram and get no engram contribution; text-only needs no mask
        engram_mask = None if image_mask is None else ~image_mask
        engram_hashes = self.engram_hash(input_ids, start_pos, engram_mask) if self.engram_hash is not None else None
        h = self.embed(input_ids)
        if images is not None:
            assert start_pos == 0, "image spans must be prefilled in a single chunk"
            self.merge_image_embeddings(images, h)
        # Expand to hc_mult copies for Hyper-Connections
        h = h.unsqueeze(2).repeat(1, 1, self.hc_mult, 1)
        main_hiddens = []
        pre_mix = make_identity_pre_mix(h, self.hc_mult)
        for i, layer in enumerate(self.layers):
            if layer.engram is not None:
                h = layer.engram(h, engram_hashes[:, :, layer.engram.layer_hash_index, :], engram_mask)
            # the MTP head reads the attention input of its target layers, not their output
            if i in self.target_layer_ids:
                main_hiddens.append(h.mean(dim=2))
            h, pre_mix = layer(h, start_pos, pre_mix, image_mask)
        h = layer.hc_pre(h, pre_mix)
        logits = self.head(self.norm(h))
        output_ids = sample(logits, self.temperature)
        main_hidden = torch.cat(main_hiddens, dim=-1) if main_hiddens else None
        return output_ids, logits, main_hidden

class Attention(nn.Module):
    """Latent attention over two KV sources at once, concatenated into one `sparse_attn` call: a
    sliding window of raw KV, plus -- when compress_ratio > 0 -- `index_topk` compressed positions
    reaching further back. Q and the output projection are both low-rank, the latter grouped.

    compress_ratio > 0 does not mean the layer compresses its own KV: only kv_source_layers do,
    the rest read that same cache.
    """

    def __init__(self, layer_id: int, args: ModelArgs):
        super().__init__()
        self.layer_id = layer_id
        self.dim = args.dim
        self.n_heads = args.n_heads
        self.n_local_heads = args.n_heads // world_size
        self.q_lora_rank = args.q_lora_rank
        self.o_lora_rank = args.o_lora_rank
        self.head_dim = args.head_dim
        self.rope_head_dim = args.rope_head_dim
        self.nope_head_dim = args.head_dim - args.rope_head_dim
        self.n_groups = args.o_groups
        self.n_local_groups = self.n_groups // world_size
        self.window_size = args.window_size
        self.compress_ratio = args.compress_ratios[layer_id]
        self.eps = args.norm_eps

        self.attn_sink = nn.Parameter(torch.empty(self.n_local_heads, dtype=torch.float32))
        self.wq_a = Linear(self.dim, self.q_lora_rank)
        self.q_norm = RMSNorm(self.q_lora_rank, self.eps)
        self.wq_b = ColumnParallelLinear(self.q_lora_rank, self.n_heads * self.head_dim)
        self.wkv = Linear(self.dim, self.head_dim)
        self.kv_norm = RMSNorm(self.head_dim, self.eps)
        self.wo_a = ColumnParallelLinear(
            self.n_heads * self.head_dim // self.n_groups,
            self.n_groups * args.o_lora_rank,
            dtype=torch.bfloat16,
        )
        self.wo_b = RowParallelLinear(self.n_groups * args.o_lora_rank, self.dim)
        self.softmax_scale = self.head_dim**-0.5

        is_backbone = layer_id < args.n_layers
        self.is_kv_source = is_backbone and layer_id in args.kv_source_layers
        self.is_index_source = is_backbone and layer_id in args.index_source_layers
        self.compressor: Compressor | None = None
        self.indexer: Indexer | None = None
        if self.is_kv_source:
            self.compressor = Compressor(args, layer_id)
        if self.is_index_source:
            self.indexer = Indexer(args, layer_id)

        self.window_kv_cache: torch.Tensor
        self.register_buffer(
            "window_kv_cache",
            torch.zeros(args.max_batch_size, args.window_size, self.head_dim),
            persistent=False,
        )
        if self.is_kv_source:
            self.compress_kv_cache: torch.Tensor
            self.register_buffer(
                "compress_kv_cache",
                torch.zeros(
                    args.max_batch_size,
                    args.max_seq_len // self.compress_ratio,
                    self.head_dim,
                ),
                persistent=False,
            )
        if self.compress_ratio:
            original_seq_len, rope_theta = (
                args.original_seq_len,
                args.compress_rope_theta,
            )
        else:
            # disable YaRN and use base rope_theta in pure sliding-window attention
            original_seq_len, rope_theta = 0, args.rope_theta
        freqs_cis = precompute_freqs_cis(
            self.rope_head_dim,
            args.max_seq_len,
            original_seq_len,
            rope_theta,
            args.rope_factor,
            args.beta_fast,
            args.beta_slow,
        )
        self.freqs_cis: torch.Tensor
        self.register_buffer("freqs_cis", freqs_cis, persistent=False)

class SharedAttentionRuntime:
    """What attention layers hand down the stack instead of recomputing. Layers run in order and
    every source writes before its consumers read, so one slot each is enough and nothing needs
    resetting between forwards. Sources: compress_kv and index_k from kv_source_layers, topk_idxs
    from index_source_layers, candidates from candidate_source_layer."""

    def __init__(self):
        self.compress_kv: torch.Tensor | None = None
        self.index_k: torch.Tensor | None = None
        self.topk_idxs: torch.Tensor | None = None
        self.candidates: torch.Tensor | None = None


# Only ever one model per process, same as world_size / rank / default_dtype above.
shared_attn = SharedAttentionRuntime()

{
    "vocab_size": 129280,
    "dim": 5120,
    "moe_inter_dim": 2304,
    "n_layers": 40,
    "n_mtp_layers": 3,
    "dspark_block_size": 5,
    "dspark_noise_token_id": 128799,
    "dspark_target_layer_ids": [37, 38, 39],
    "dspark_markov_rank": 256,
    "dspark_n_routed_experts": 128,
    "dspark_n_activated_experts": 3,
    "n_heads": 64,
    "n_routed_experts": 384,
    "n_shared_experts": 1,
    "n_activated_experts": 6,
    "score_func": "sqrtsoftplus",
    "route_scale": 1.5,
    "swiglu_limit": 10.0,
    "q_lora_rank": 1280,
    "head_dim": 512,
    "rope_head_dim": 64,
    "norm_eps": 1e-20,
    "o_groups": 8,
    "o_lora_rank": 1024,
    "window_size": 128,
    "kv_source_layers": [2, 8, 14, 20],
    "index_source_layers": [2, 8, 14, 20, 24, 28, 32, 36],
    "original_seq_len": 65536,
    "rope_theta": 10000,
    "rope_factor": 16,
    "beta_fast": 32,
    "beta_slow": 1,
    "index_n_heads": 32,
    "index_head_dim": 128,
    "index_topk": 512,
    "candidate_source_layer": 20,
    "candidate_topk_blocks": 2048,
    "candidate_block_size": 8,
    "hc_mult": 4,
    "hc_sinkhorn_iters": 20,
    "hc_eps": 1e-06,
    "engram_layer_ids": [1, 14],
    "engram_vocab_size": 16000000,
    "engram_num_embeddings": [384006168, 384016682],
    "engram_max_ngram_size": 4,
    "engram_pad_id": 2,
    "engram_compressed_vocab_size": 99092,
    "dtype": "fp8",
    "expert_dtype": "fp4",
    "compress_rope_theta": 160000,
    "compress_ratios": [0, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0],
    "vision_n_layers": 32,
    "vision_dim": 1024,
    "vision_n_heads": 16,
    "vision_inter_dim": 2816,
    "vision_patch_size": 14,
    "vision_downsample_ratio": 3,
    "vision_max_n_token": 1024,
    "vision_min_pixels": 295936,
    "vision_max_wh_ratio": null,
    "image_token_id": 129264,
    "engram_n_heads": 8,
    "engram_head_dim": 256,
    "vision_rope_theta": 10000
}

    def hc_mixes(self, x: torch.Tensor, hc_fn: torch.Tensor, hc_scale: torch.Tensor, hc_base: torch.Tensor):
        """x: [b,s,hc,d], hc_fn: [mix_hc, hc*d], hc_scale: [3], hc_base: [mix_hc]. Returns the
        pre / post / comb coefficients, split out of one projection of the flattened stream."""
        # normalized over the whole flattened hc*d stream, one statistic per token
        x = x.flatten(2).float()
        rsqrt = torch.rsqrt(x.square().mean(-1, keepdim=True) + self.norm_eps)
        mixes = F.linear(x, hc_fn) * rsqrt
        return hc_split_sinkhorn(mixes, hc_scale, hc_base, self.hc_mult, self.hc_sinkhorn_iters, self.hc_eps)

    def hc_pre(self, x: torch.Tensor, pre_mix: torch.Tensor):
        """Collapse the hc copies into one, weighted by pre_mix. [b,s,hc,d] x [b,s,hc] -> [b,s,d]"""
        y = torch.sum(pre_mix.unsqueeze(-1) * x.float(), dim=2)
        return y.to(x.dtype)

    def hc_post(self, x: torch.Tensor, residual: torch.Tensor, post: torch.Tensor, comb: torch.Tensor):
        """Expand the sublayer output back to hc copies and mix the residual in through `comb`.
        x: [b,s,d], residual: [b,s,hc,d], post: [b,s,hc], comb: [b,s,hc,hc] -> [b,s,hc,d]"""
        y = post.unsqueeze(-1) * x.unsqueeze(-2) + torch.sum(comb.unsqueeze(-1) * residual.unsqueeze(-2), dim=2)
        return y.type_as(x)