common.h

#pragma once

#include <cstddef>
#include <cassert>
#include <cmath>
#include <iostream>
#include <fstream>
#include <sstream>
#include <memory>
#include <source_location>
#include <vector>
#include <list>
#include <stack>
#include <map>
#include <unordered_map>
#include <set>
#include <any>
#include <variant>
#include <optional>
#include <chrono>
#include <functional>
#include <cuda_runtime_api.h>
#include <cublas_v2.h>
#include <spdlog/spdlog.h>

class CUDAError : public std::runtime_error {
public:
    CUDAError(cudaError_t errorCode, std::source_location location) 
        : std::runtime_error(format(errorCode, location)), errorCode(errorCode), location(location) {}

public:
    const cudaError_t errorCode;
    const std::source_location location;

private:
    static std::string format(cudaError_t errorCode, std::source_location location) {
        return spdlog::fmt_lib::format("CUDA error: {} (at {}:{})", 
            cudaGetErrorString(errorCode), location.file_name(), location.line());
    }
};

inline cudaError_t checkCUDA(cudaError_t retValue, const std::source_location location = std::source_location::current()) {
    if (retValue != cudaSuccess) {
        (void)cudaGetLastError();
        throw CUDAError(retValue, location);
    }
    return retValue;
}

inline cublasStatus_t checkCUBLAS(cublasStatus_t retValue, const std::source_location location = std::source_location::current()) {
    if (retValue != CUBLAS_STATUS_SUCCESS) {
        throw std::runtime_error(spdlog::fmt_lib::format("CUBLAS error: {} (at {}:{})", 
            cublasGetStatusString(retValue), location.file_name(), location.line()));
    }
    return retValue;
}

inline thread_local std::stack<cudaStream_t> stackCUDAStreams;

inline cudaStream_t getCurrentCUDAStream() {
    if (stackCUDAStreams.empty()) {
        return 0;
    }
    return stackCUDAStreams.top();
}

struct CUDAStreamContext {
    cudaStream_t stream;

    CUDAStreamContext(cudaStream_t stream) : stream(stream) {
        stackCUDAStreams.push(stream);
    }
    CUDAStreamContext(const CUDAStreamContext &) = delete;
    CUDAStreamContext(CUDAStreamContext &&) = delete;
    
    ~CUDAStreamContext() {
        assert(stackCUDAStreams.top() == stream);
        stackCUDAStreams.pop();
    }
};

struct CUDAStreamWrapper {
    cudaStream_t stream;

    CUDAStreamWrapper() {
        checkCUDA(cudaStreamCreate(&stream));
    }
    CUDAStreamWrapper(const CUDAStreamWrapper &) = delete;
    CUDAStreamWrapper(CUDAStreamWrapper &&) = delete;

    ~CUDAStreamWrapper() {
        checkCUDA(cudaStreamDestroy(stream));
    }
};

struct CUDAEventWrapper {
    cudaEvent_t event;

    CUDAEventWrapper(unsigned int flags = cudaEventDefault) {
        checkCUDA(cudaEventCreateWithFlags(&event, flags));
    }
    CUDAEventWrapper(const CUDAEventWrapper &) = delete;
    CUDAEventWrapper(CUDAEventWrapper &&) = delete;

    ~CUDAEventWrapper() {
        checkCUDA(cudaEventDestroy(event));
    }
};


/**
 * 1. hold one when entered from external code (set `device` to -1 to avoid device change)
 * 2. hold one when switching device
 * 3. hold one with `disableCache` when calling external code that may change the device
 */
class CUDADeviceContext {
public:
    CUDADeviceContext(int device = -1, bool disableCache = false) : disableCache(disableCache) {
        if (cacheDisabled()) {
            // no previous context => we might entered from external code, reset cache
            // previous context is reset on => external code may be executed, reset
            currentDeviceCache = -1;
        }
        
        ctxs.push(this);
        lastDevice = getDevice();
        if (device >= 0) {
            setDevice(device);
        }

        if (disableCache) {
            // we are about to call external code, reset cache
            currentDeviceCache = -1;
        }
    }
    CUDADeviceContext(const CUDADeviceContext &) = delete;
    CUDADeviceContext(CUDADeviceContext &&) = delete;

    ~CUDADeviceContext() {
        if (disableCache) {
            // retured from external code, cache is not reliable, reset
            currentDeviceCache = -1;
        }

        setDevice(lastDevice);
        assert(ctxs.top() == this);
        ctxs.pop();

        if (cacheDisabled()) {
            // ctxs.empty() => we are about to return to external code, reset cache
            // otherwise => we are a nested context in a previous context with reset on, we might continue to execute external code, reset
            currentDeviceCache = -1;
        }
    }

    const bool disableCache;
    int lastDevice;


public:
    static int getDevice() {
        int idx = -1;
        if (cacheDisabled() || currentDeviceCache < 0) {
            checkCUDA(cudaGetDevice(&idx));
        } else {
            idx = currentDeviceCache;
        }
        currentDeviceCache = cacheDisabled() ? -1 : idx;
        return idx;
    }
private:
    static void setDevice(int idx) {
        // TODO: deal with stream when switching device
        assert(idx >= 0);
        if (!cacheDisabled() && currentDeviceCache == idx) {
            return;
        }
        checkCUDA(cudaSetDevice(idx));
        currentDeviceCache = cacheDisabled() ? -1 : idx;
    }

private:
    static inline thread_local std::stack<CUDADeviceContext *> ctxs;
    static inline thread_local int currentDeviceCache = -1;

    static bool cacheDisabled() {
        return ctxs.empty() || ctxs.top()->disableCache;
    }
};

inline cudaDeviceProp *getCurrentDeviceProperties() {
    static thread_local std::map<int, cudaDeviceProp> props;

    int deviceId = CUDADeviceContext::getDevice();
    if (!props.contains(deviceId)) {
        cudaDeviceProp prop;
        checkCUDA(cudaGetDeviceProperties(&prop, deviceId));
        props[deviceId] = prop;
    }
    return &props.at(deviceId);
}

template<typename T>
constexpr T ceilDiv(T a, T b) {
    return (a + b - 1) / b;
}

template<typename T>
constexpr int log2Up(T value) {
   if (value <= 0)
       return 0;
   if (value == 1)
       return 0;
   return log2Up((value + 1) / 2) + 1;
}

struct CUBLASWrapper {
    cublasHandle_t handle = nullptr;

    CUBLASWrapper() {
        checkCUBLAS(cublasCreate(&handle));
    }
    CUBLASWrapper(CUBLASWrapper &&) = delete;
    CUBLASWrapper(const CUBLASWrapper &&) = delete;
    ~CUBLASWrapper() {
        if (handle) {
            checkCUBLAS(cublasDestroy(handle));
        }
    }
};

inline std::shared_ptr<CUBLASWrapper> getCUBLAS() {
    static thread_local std::weak_ptr<CUBLASWrapper> inst;
    std::shared_ptr<CUBLASWrapper> result = inst.lock();
    if (result) {
        return result;
    }
    result = std::make_shared<CUBLASWrapper>();
    inst = result;
    return result;
}