backend/cpp/llama/utils.hpp

// https://github.com/ggerganov/llama.cpp/blob/master/examples/server/utils.hpp

#pragma once

#include <string>
#include <vector>
#include <set>
#include <mutex>
#include <condition_variable>
#include <unordered_map>

#include "json.hpp"

#include "../llava/clip.h"

using json = nlohmann::json;

extern bool server_verbose;

#ifndef SERVER_VERBOSE
#define SERVER_VERBOSE 1
#endif

#if SERVER_VERBOSE != 1
#define LOG_VERBOSE(MSG, ...)
#else
#define LOG_VERBOSE(MSG, ...)                                            \
    do                                                                   \
    {                                                                    \
        if (server_verbose)                                              \
        {                                                                \
            server_log("VERBOSE", __func__, __LINE__, MSG, __VA_ARGS__); \
        }                                                                \
    } while (0)
#endif

#define LOG_ERROR(  MSG, ...) server_log("ERROR",   __func__, __LINE__, MSG, __VA_ARGS__)
#define LOG_WARNING(MSG, ...) server_log("WARNING", __func__, __LINE__, MSG, __VA_ARGS__)
#define LOG_INFO(   MSG, ...) server_log("INFO",    __func__, __LINE__, MSG, __VA_ARGS__)

//
// parallel
//

enum server_state {
    SERVER_STATE_LOADING_MODEL,  // Server is starting up, model not fully loaded yet
    SERVER_STATE_READY,          // Server is ready and model is loaded
    SERVER_STATE_ERROR           // An error occurred, load_model failed
};

enum task_type {
    TASK_TYPE_COMPLETION,
    TASK_TYPE_CANCEL,
    TASK_TYPE_NEXT_RESPONSE
};

struct task_server {
    int id = -1; // to be filled by llama_server_queue
    int target_id;
    task_type type;
    json data;
    bool infill_mode = false;
    bool embedding_mode = false;
    int multitask_id = -1;
};

struct task_result {
    int id;
    int multitask_id = -1;
    bool stop;
    bool error;
    json result_json;
};

struct task_multi {
    int id;
    std::set<int> subtasks_remaining{};
    std::vector<task_result> results{};
};

// TODO: can become bool if we can't find use of more states
enum slot_state
{
    IDLE,
    PROCESSING,
};

enum slot_command
{
    NONE,
    LOAD_PROMPT,
    RELEASE,
};

struct slot_params
{
    bool stream       = true;
    bool cache_prompt = false; // remember the prompt to avoid reprocessing all prompt

    uint32_t seed      = -1; // RNG seed
    int32_t  n_keep    =  0; // number of tokens to keep from initial prompt
    int32_t  n_predict = -1; // new tokens to predict

    std::vector<std::string> antiprompt;

    json input_prefix;
    json input_suffix;
};

struct slot_image
{
    int32_t id;

    bool request_encode_image = false;
    float * image_embedding = nullptr;
    int32_t image_tokens = 0;

    clip_image_u8 * img_data;

    std::string prefix_prompt; // before of this image
};

// completion token output with probabilities
struct completion_token_output
{
    struct token_prob
    {
        llama_token tok;
        float prob;
    };

    std::vector<token_prob> probs;
    llama_token tok;
    std::string text_to_send;
};

static inline void server_log(const char *level, const char *function, int line,
                       const char *message, const nlohmann::ordered_json &extra)
{
    nlohmann::ordered_json log
    {
        {"timestamp", time(nullptr)},
        {"level",     level},
        {"function",  function},
        {"line",      line},
        {"message",   message},
    };

    if (!extra.empty())
    {
        log.merge_patch(extra);
    }

    const std::string str = log.dump(-1, ' ', false, json::error_handler_t::replace);
    printf("%.*s\n", (int)str.size(), str.data());
    fflush(stdout);
}

//
// server utils
//

template <typename T>
static T json_value(const json &body, const std::string &key, const T &default_value)
{
    // Fallback null to default value
    return body.contains(key) && !body.at(key).is_null()
        ? body.value(key, default_value)
        : default_value;
}

inline std::string format_chatml(std::vector<json> messages)
{
    std::ostringstream chatml_msgs;

    for (auto it = messages.begin(); it != messages.end(); ++it) {
        chatml_msgs << "<|im_start|>"
                    << json_value(*it, "role",    std::string("user")) << '\n';
        chatml_msgs << json_value(*it, "content", std::string(""))
                    << "<|im_end|>\n";
    }

    chatml_msgs << "<|im_start|>assistant" << '\n';

    return chatml_msgs.str();
}

//
// work queue utils
//

struct llama_server_queue {
    int id = 0;
    std::mutex mutex_tasks;
    // queues
    std::vector<task_server> queue_tasks;
    std::vector<task_server> queue_tasks_deferred;
    std::vector<task_multi> queue_multitasks;
    std::condition_variable condition_tasks;
    // callback functions
    std::function<void(task_server&)> callback_new_task;
    std::function<void(task_multi&)> callback_finish_multitask;
    std::function<void(void)> callback_all_task_finished;

    // Add a new task to the end of the queue
    int post(task_server task) {
        std::unique_lock<std::mutex> lock(mutex_tasks);
        if (task.id == -1) {
            task.id = id++;
        }
        queue_tasks.push_back(std::move(task));
        condition_tasks.notify_one();
        return task.id;
    }

    // Add a new task, but defer until one slot is available
    void defer(task_server task) {
        std::unique_lock<std::mutex> lock(mutex_tasks);
        queue_tasks_deferred.push_back(std::move(task));
    }

    // Get the next id for creating anew task
    int get_new_id() {
        std::unique_lock<std::mutex> lock(mutex_tasks);
        return id++;
    }

    // Register function to process a new task
    void on_new_task(std::function<void(task_server&)> callback) {
        callback_new_task = callback;
    }

    // Register function to process a multitask
    void on_finish_multitask(std::function<void(task_multi&)> callback) {
        callback_finish_multitask = callback;
    }

    // Register the function to be called when the batch of tasks is finished
    void on_all_tasks_finished(std::function<void(void)> callback) {
        callback_all_task_finished = callback;
    }

    // Call when the state of one slot is changed
    void notify_slot_changed() {
        // move deferred tasks back to main loop
        std::unique_lock<std::mutex> lock(mutex_tasks);
        for (auto & task : queue_tasks_deferred) {
            queue_tasks.push_back(std::move(task));
        }
        queue_tasks_deferred.clear();
    }

    // Start the main loop. This call is blocking
    [[noreturn]]
    void start_loop() {
        while (true) {
            // new task arrived
            LOG_VERBOSE("have new task", {});
            {
                while (true)
                {
                    std::unique_lock<std::mutex> lock(mutex_tasks);
                    if (queue_tasks.empty()) {
                        lock.unlock();
                        break;
                    }
                    task_server task = queue_tasks.front();
                    queue_tasks.erase(queue_tasks.begin());
                    lock.unlock();
                    LOG_VERBOSE("callback_new_task", {});
                    callback_new_task(task);
                }
                LOG_VERBOSE("callback_all_task_finished", {});
                // process and update all the multitasks
                auto queue_iterator = queue_multitasks.begin();
                while (queue_iterator != queue_multitasks.end())
                {
                    if (queue_iterator->subtasks_remaining.empty())
                    {
                        // all subtasks done == multitask is done
                        task_multi current_multitask = *queue_iterator;
                        callback_finish_multitask(current_multitask);
                        // remove this multitask
                        queue_iterator = queue_multitasks.erase(queue_iterator);
                    }
                    else
                    {
                        ++queue_iterator;
                    }
                }
                // all tasks in the current loop is finished
                callback_all_task_finished();
            }
            LOG_VERBOSE("wait for new task", {});
            // wait for new task
            {
                std::unique_lock<std::mutex> lock(mutex_tasks);
                if (queue_tasks.empty()) {
                    condition_tasks.wait(lock, [&]{
                        return !queue_tasks.empty();
                    });
                }
            }
        }
    }

    //
    // functions to manage multitasks
    //

    // add a multitask by specifying the id of all subtask (subtask is a task_server)
    void add_multitask(int multitask_id, std::vector<int>& sub_ids)
    {
        std::lock_guard<std::mutex> lock(mutex_tasks);
        task_multi multi;
        multi.id = multitask_id;
        std::copy(sub_ids.begin(), sub_ids.end(), std::inserter(multi.subtasks_remaining, multi.subtasks_remaining.end()));
        queue_multitasks.push_back(multi);
    }

    // updatethe remaining subtasks, while appending results to multitask
    void update_multitask(int multitask_id, int subtask_id, task_result& result)
    {
        std::lock_guard<std::mutex> lock(mutex_tasks);
        for (auto& multitask : queue_multitasks)
        {
            if (multitask.id == multitask_id)
            {
                multitask.subtasks_remaining.erase(subtask_id);
                multitask.results.push_back(result);
            }
        }
    }
};

struct llama_server_response {
    typedef std::function<void(int, int, task_result&)> callback_multitask_t;
    callback_multitask_t callback_update_multitask;
    // for keeping track of all tasks waiting for the result
    std::set<int> waiting_task_ids;
    // the main result queue
    std::vector<task_result> queue_results;
    std::mutex mutex_results;
    std::condition_variable condition_results;

    void add_waiting_task_id(int task_id) {
        std::unique_lock<std::mutex> lock(mutex_results);
        waiting_task_ids.insert(task_id);
    }

    void remove_waiting_task_id(int task_id) {
        std::unique_lock<std::mutex> lock(mutex_results);
        waiting_task_ids.erase(task_id);
    }

    // This function blocks the thread until there is a response for this task_id
    task_result recv(int task_id) {
        while (true)
        {
            std::unique_lock<std::mutex> lock(mutex_results);
            condition_results.wait(lock, [&]{
                return !queue_results.empty();
            });
            LOG_VERBOSE("condition_results unblock", {});

            for (int i = 0; i < (int) queue_results.size(); i++)
            {
                if (queue_results[i].id == task_id)
                {
                    assert(queue_results[i].multitask_id == -1);
                    task_result res = queue_results[i];
                    queue_results.erase(queue_results.begin() + i);
                    return res;
                }
            }
        }

        // should never reach here
    }

    // Register the function to update multitask
    void on_multitask_update(callback_multitask_t callback) {
        callback_update_multitask = callback;
    }

    // Send a new result to a waiting task_id
    void send(task_result result) {
        std::unique_lock<std::mutex> lock(mutex_results);
        LOG_VERBOSE("send new result", {});
        for (auto& task_id : waiting_task_ids) {
            // LOG_TEE("waiting task id %i \n", task_id);
            // for now, tasks that have associated parent multitasks just get erased once multitask picks up the result
            if (result.multitask_id == task_id)
            {
                LOG_VERBOSE("callback_update_multitask", {});
                callback_update_multitask(task_id, result.id, result);
                continue;
            }

            if (result.id == task_id)
            {
                LOG_VERBOSE("queue_results.push_back", {});
                queue_results.push_back(result);
                condition_results.notify_one();
                return;
            }
        }
    }
};

//
// base64 utils (TODO: move to common in the future)
//

static const std::string base64_chars =
             "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
             "abcdefghijklmnopqrstuvwxyz"
             "0123456789+/";

static inline bool is_base64(uint8_t c)
{
    return (isalnum(c) || (c == '+') || (c == '/'));
}

static inline std::vector<uint8_t> base64_decode(const std::string & encoded_string)
{
    int i = 0;
    int j = 0;
    int in_ = 0;

    int in_len = encoded_string.size();

    uint8_t char_array_4[4];
    uint8_t char_array_3[3];

    std::vector<uint8_t> ret;

    while (in_len-- && (encoded_string[in_] != '=') && is_base64(encoded_string[in_]))
    {
        char_array_4[i++] = encoded_string[in_]; in_++;
        if (i == 4)
        {
            for (i = 0; i <4; i++)
            {
                char_array_4[i] = base64_chars.find(char_array_4[i]);
            }

            char_array_3[0] = ((char_array_4[0]      ) << 2) + ((char_array_4[1] & 0x30) >> 4);
            char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
            char_array_3[2] = ((char_array_4[2] & 0x3) << 6) +   char_array_4[3];

            for (i = 0; (i < 3); i++)
            {
                ret.push_back(char_array_3[i]);
            }
            i = 0;
        }
    }

    if (i)
    {
        for (j = i; j <4; j++)
        {
            char_array_4[j] = 0;
        }

        for (j = 0; j <4; j++)
        {
            char_array_4[j] = base64_chars.find(char_array_4[j]);
        }

        char_array_3[0] = ((char_array_4[0]      ) << 2) + ((char_array_4[1] & 0x30) >> 4);
        char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
        char_array_3[2] = ((char_array_4[2] & 0x3) << 6) +   char_array_4[3];

        for (j = 0; (j < i - 1); j++)
        {
            ret.push_back(char_array_3[j]);
        }
    }

    return ret;
}

//
// random string / id
//

static std::string random_string()
{
    static const std::string str("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz");

    std::random_device rd;
    std::mt19937 generator(rd());

    std::string result(32, ' ');

    for (int i = 0; i < 32; ++i) {
        result[i] = str[generator() % str.size()];
    }

    return result;
}

static std::string gen_chatcmplid()
{
    std::stringstream chatcmplid;
    chatcmplid << "chatcmpl-" << random_string();
    return chatcmplid.str();
}