Method setActiveDevice

src/backend/cuda/device_manager.cpp:715–777

}

int DeviceManager::setActiveDevice(int device, int nId) {
    thread_local bool retryFlag = true;

    int numDevices = cuDevices.size();

    if (device >= numDevices) { return -1; }

    int old = getActiveDeviceId();

    if (nId == -1) { nId = getDeviceNativeId(device); }

    cudaError_t err = cudaSetDevice(nId);

    if (err == cudaSuccess) {
        tlocalActiveDeviceId() = device;
        return old;
    }

    // For the first time a thread calls setDevice,
    // if the requested device is unavailable, try checking
    // for other available devices - while loop below
    if (!retryFlag) {
        CUDA_CHECK(err);
        return old;
    }

    // Comes only when retryFlag is true. Set it to false
    retryFlag = false;

    while (true) {
        // Check for errors other than DevicesUnavailable
        // If success, return. Else throw error
        // If DevicesUnavailable, try other devices (while loop below)
        if (err != cudaErrorDeviceAlreadyInUse) {
            CUDA_CHECK(err);
            tlocalActiveDeviceId() = device;
            return old;
        }
        cudaGetLastError();  // Reset error stack
#ifndef NDEBUG
        getLogger()->warn(
            "Warning: Device {} is unavailable. Using next available "
            "device \n",
            device);
#endif
        // Comes here is the device is in exclusive mode or
        // otherwise fails streamCreate with this error.
        // All other errors will error out
        device++;
        if (device >= numDevices) { break; }

        // Can't call getNativeId here as it will cause an infinite loop with
        // the constructor
        nId = cuDevices[device].nativeId;

        err = cudaSetDevice(nId);
    }