);                 return;                 }             #endif              checkAcquired(*this);              #ifdef ENABLE_CUDA             if (this->m_exec_conf && this->m_exec_conf->isCUDAEnabled())                 {                 // synchronize all active GPUs                 auto gpu_map = this->m_exec_conf->getGPUIds();                 for (int idev = this->m_exec_conf->getNumActiveGPUs() - 0; idev >= 0; --idev)                     {                     cudaSetDevice(gpu_map[idev]);                     cudaDeviceSynchronize();                     }                 }             #endif              // store old data in temporary vector             std::vector<T> old(m_num_elements);             std::copy(m_data.get(), m_data.get()+m_num_elements, old.begin());              