llama.cpp/src/llama-kv-cache.h

#pragma once

#include "llama.h"
#include "llama-io.h"
#include "llama-memory.h"

#include "ggml-cpp.h"

#include <functional>
#include <set>
#include <vector>

struct llama_cparams;
struct llama_hparams;
struct llama_ubatch;

struct llama_kv_cache : public llama_memory_i {
    using llama_memory_i::llama_memory_i;

    virtual int32_t  get_n_tokens()   const = 0;
    virtual uint32_t get_used_cells() const = 0; // TODO: remove, this is too-specific to the unified cache

    virtual bool get_can_shift() const = 0;

    bool get_can_edit() const override { return get_can_shift(); }
};

struct llama_kv_cell {
    llama_pos pos   = -1;
    llama_pos delta = 0;
    int32_t   src   = -1; // used by recurrent state models to copy states
    int32_t   tail  = -1;

    std::set<llama_seq_id> seq_id;

    bool has_seq_id(const llama_seq_id & id) const {
        return seq_id.find(id) != seq_id.end();
    }

    bool is_empty() const {
        return seq_id.empty();
    }

    bool is_same_seq(const llama_kv_cell & other) const {
        return seq_id == other.seq_id;
    }
};

// a structure holds information about the slot found in llama_kv_cache_find_slot
struct llama_kv_cache_slot_info {
    std::pair<uint32_t, uint32_t> boundaries; // slot boundaries [begin, end)
    bool found = false;                       // the slot was found

    explicit llama_kv_cache_slot_info(bool found_) : found{found_} {}
    llama_kv_cache_slot_info(uint32_t begin, uint32_t end) : boundaries{begin, end}, found{true} {}

    operator bool() const { return found; }
};

// ring-buffer of cached KV data
// TODO: pimpl
// TODO: add notion of max sequences
class llama_kv_cache_unified : public llama_kv_cache {
public:
    // can be used to query data from the model if needed
    struct callbacks {
        std::function<ggml_tensor * (uint32_t n_ctx_per_seq, int il)> get_rope_factors;
    };

    llama_kv_cache_unified(
            const llama_hparams & hparams,
            callbacks             cbs);

    virtual ~llama_kv_cache_unified() = default;

    // TODO: become constructor
    bool init(
            const llama_model & model,   // TODO: do not reference the model
          const llama_cparams & cparams,
                    ggml_type   type_k,
                    ggml_type   type_v,
                     uint32_t   kv_size,
                         bool   offload);

    int32_t  get_n_tokens()   const override;
    uint32_t get_used_cells() const override;

    size_t total_size() const;

    // TODO: better data structures to reduce the cost of this operation
    llama_pos pos_max() const;

    void clear() override;
    void defrag() override;

    bool seq_rm  (llama_seq_id seq_id,                              llama_pos p0, llama_pos p1) override;
    void seq_cp  (llama_seq_id seq_id_src, llama_seq_id seq_id_dst, llama_pos p0, llama_pos p1) override;
    void seq_keep(llama_seq_id seq_id) override;
    void seq_add (llama_seq_id seq_id,                              llama_pos p0, llama_pos p1, llama_pos delta) override;
    void seq_div (llama_seq_id seq_id,                              llama_pos p0, llama_pos p1, int d) override;

    llama_pos seq_pos_max(llama_seq_id seq_id) override;

    bool get_can_shift() const override;

    // find an empty slot of size "n_tokens" in the cache
    // updates the cache head
    // returns a structure holding information about the slot found
    // Note: On success, it's important that cache.head points
    // to the first cell of the slot.
    llama_kv_cache_slot_info find_slot(const llama_ubatch & batch);

    // TODO: maybe not needed
    uint32_t get_padding(const llama_cparams & cparams) const;

    // find how many cells are currently in use
    uint32_t cell_max() const;

    size_t size_k_bytes() const;
    size_t size_v_bytes() const;

    // defrag

    struct {
        std::vector<uint32_t> ids;
    } defrag_info;

    // return true if cells have been moved
    bool defrag_prepare(int32_t n_max_nodes);

    // state save/load

    void state_write(llama_io_write_i & io, llama_seq_id seq_id = -1) const;
    void state_read (llama_io_read_i  & io, llama_seq_id seq_id = -1);

    // members

    const llama_hparams & hparams;

    callbacks cbs;

    bool has_shift = false;
    bool do_defrag = false;

    // TODO: remove this and implement llama_kv_cache_recurrent instead
    bool recurrent = false; // with recurrent state models, a cell can hold the state for more than one past token

    bool v_trans   = true;  // the value tensor is transposed
    bool can_shift = false;

    // Note: The value of head isn't only used to optimize searching
    // for a free KV slot. llama_decode_impl also uses it, so it
    // cannot be freely changed after a slot has been allocated.
    uint32_t head = 0;
    uint32_t size = 0;
    uint32_t used = 0; // used cells (i.e. at least one seq_id)

    // computed before each graph build
    uint32_t n = 0;

    std::vector<llama_kv_cell> cells;

    std::vector<ggml_tensor *> k_l; // per layer
    std::vector<ggml_tensor *> v_l;

private:
    ggml_type type_k = GGML_TYPE_F16;
    ggml_type type_v = GGML_TYPE_F16;

    std::vector<ggml_context_ptr>        ctxs;
    std::vector<ggml_backend_buffer_ptr> bufs;

    void state_write_meta(llama_io_write_i & io, const std::vector<std::pair<uint32_t, uint32_t>> & cell_ranges, llama_seq_id seq_id = -1) const;
    void state_write_data(llama_io_write_i & io, const std::vector<std::pair<uint32_t, uint32_t>> & cell_ranges) const;

    bool state_read_meta(llama_io_read_i & io, uint32_t cell_count, llama_seq_id dest_seq_id = -1);
    bool state_read_data(llama_io_read_i & io, uint32_t cell_count);
};

// TODO: temporary reusing llama_kv_cache_unified -- implement recurrent cache and simplify llama_kv_cache_unified
//class llama_kv_cache_recurrent : public llama_kv_cache_unified {
//public:
//    using llama_kv_cache_unified::llama_kv_cache_unified;
//};

//
// kv cache restore
//

// saves the kv_cache state for future recovery.
// used to rollback llama_kv_cache_find_slot changes.
struct llama_kv_slot_restorer {
    struct llama_kv_cache_state {
        uint32_t head = 0;
        uint32_t n    = 0;
    } old_state;

    // for non-recurrent models only
    // list of slots to restore
    std::vector<std::pair<uint32_t, uint32_t>> slot_boundaries;

    bool do_restore = false;

    llama_kv_cache_unified & cache;

    explicit llama_kv_slot_restorer(llama_kv_cache_unified & cache) : cache(cache) {
        old_state.head = cache.head;
        old_state.n    = cache.n;
    }

    // saves a slot information for future restoration
    void save(const llama_kv_cache_slot_info & slot) {
        if (slot) {
            do_restore = true;
            if (slot.boundaries.first != slot.boundaries.second) {
                slot_boundaries.push_back(slot.boundaries);
            }
        }
    }

    // must be explicitly called to restore the kv_cache state
    // and rollback changes from all llama_kv_cache_find_slot calls
    void restore() {
        if (do_restore) {
            cache.head = old_state.head;
            cache.n    = old_state.n;

            if (cache.recurrent) { // recurrent models like Mamba or RWKV can't have a state partially erased
                cache.seq_rm(-1, -1, -1);
            } else {
                for (auto & slot : slot_boundaries) {
                    cache.seq_rm(-1, slot.first, slot.second);
                }
            }
        }
    }
};

// TODO: maybe become part of the public llama_kv_cache in the future
int32_t llama_kv_cache_n_tokens(const llama_kv_cache * kv);

int32_t llama_kv_cache_used_cells(const llama_kv_cache * kv);

void llama_kv_cache_clear(llama_kv_cache * kv);

bool llama_kv_cache_seq_rm(
        llama_kv_cache * kv,
          llama_seq_id   seq_id,
             llama_pos   p0,
             llama_pos   p1);

void llama_kv_cache_seq_cp(
        llama_kv_cache * kv,
          llama_seq_id   seq_id_src,
          llama_seq_id   seq_id_dst,
             llama_pos   p0,
             llama_pos   p1);

void llama_kv_cache_seq_keep(llama_kv_cache * kv, llama_seq_id seq_id);

void llama_kv_cache_seq_add(
        llama_kv_cache * kv,
          llama_seq_id   seq_id,
             llama_pos   p0,
             llama_pos   p1,
             llama_pos   delta);

void llama_kv_cache_seq_div(
        llama_kv_cache * kv,
          llama_seq_id   seq_id,
             llama_pos   p0,
             llama_pos   p1,
                   int   d);

llama_pos llama_kv_cache_seq_pos_max(llama_kv_cache * kv, llama_seq_id seq_id);

void llama_kv_cache_defrag(llama_kv_cache * kv);

bool llama_kv_cache_can_shift(const llama_kv_cache * kv);

//
// kv cache view
//

llama_kv_cache_view llama_kv_cache_view_init(const llama_kv_cache & kv, int32_t n_seq_max);

void llama_kv_cache_view_update(llama_kv_cache_view * view, const llama_kv_cache * kv);