c++ - 该模板是特化的还是声明(或完全其他的东西)？

我在Nvidia的CUDA Samples n-body模拟中遇到了以下代码：template <> NBodyDemo<double> *NBodyDemo<double>::m_singleton = 0;template <> NBodyDemo<float> *NBodyDemo<float>::m_singleton = 0;该代码是否声明了指针？如果是这种情况，为什么要使用template 。我不知道这两行是干什么用的。而且，该类的ctor和dtor是私有的；人们使用Create（）方法实例化了此类。根据我的经验，这是非常不寻常的，我希望对这种编码风格背后的原因有所了解。版权声明 /* * Copyright 1993-2015 NVIDIA Corporation. All rights reserved. * * Please refer to the NVIDIA end user license agreement (EULA) associated * with this source code for terms and conditions that govern your use of * this software. Any use, reproduction, disclosure, or distribution of * this software and related documentation outside the terms of the EULA * is strictly prohibited. * */类定义template <typename T> class NBodyDemo { public: static void Create() { m_singleton = new NBodyDemo; } static void Destroy() { delete m_singleton; } static void init(int numBodies, int numDevices, int blockSize, bool usePBO, bool useHostMem, bool useCpu) { m_singleton->_init(numBodies, numDevices, blockSize, usePBO, useHostMem, useCpu); } static void reset(int numBodies, NBodyConfig config) { m_singleton->_reset(numBodies, config); } static void selectDemo(int index) { m_singleton->_selectDemo(index); } static bool compareResults(int numBodies) { return m_singleton->_compareResults(numBodies); } static void runBenchmark(int iterations) { m_singleton->_runBenchmark(iterations); } static void updateParams() { m_singleton->m_nbody->setSoftening(activeParams.m_softening); m_singleton->m_nbody->setDamping(activeParams.m_damping); } static void updateSimulation() { m_singleton->m_nbody->update(activeParams.m_timestep); } static void display() { m_singleton->m_renderer->setSpriteSize(activeParams.m_pointSize); if (useHostMem) { // This event sync is required because we are rendering from the host memory that CUDA is // writing. If we don't wait until CUDA is done updating it, we will render partially // updated data, resulting in a jerky frame rate. if (!useCpu) { cudaEventSynchronize(hostMemSyncEvent); } m_singleton->m_renderer->setPositions( m_singleton->m_nbody->getArray(BODYSYSTEM_POSITION), m_singleton->m_nbody->getNumBodies()); } else { m_singleton->m_renderer->setPBO(m_singleton->m_nbody->getCurrentReadBuffer(), m_singleton->m_nbody->getNumBodies(), (sizeof(T) > 4)); } // display particles m_singleton->m_renderer->display(displayMode); } static void getArrays(T *pos, T *vel) { T *_pos = m_singleton->m_nbody->getArray(BODYSYSTEM_POSITION); T *_vel = m_singleton->m_nbody->getArray(BODYSYSTEM_VELOCITY); memcpy(pos, _pos, m_singleton->m_nbody->getNumBodies() * 4 * sizeof(T)); memcpy(vel, _vel, m_singleton->m_nbody->getNumBodies() * 4 * sizeof(T)); } static void setArrays(const T *pos, const T *vel) { if (pos != m_singleton->m_hPos) { memcpy(m_singleton->m_hPos, pos, numBodies * 4 * sizeof(T)); } if (vel != m_singleton->m_hVel) { memcpy(m_singleton->m_hVel, vel, numBodies * 4 * sizeof(T)); } m_singleton->m_nbody->setArray(BODYSYSTEM_POSITION, m_singleton->m_hPos); m_singleton->m_nbody->setArray(BODYSYSTEM_VELOCITY, m_singleton->m_hVel); if (!benchmark && !useCpu && !compareToCPU) { m_singleton->_resetRenderer(); } } private: static NBodyDemo *m_singleton; BodySystem<T> *m_nbody; BodySystemCUDA<T> *m_nbodyCuda; BodySystemCPU<T> *m_nbodyCpu; ParticleRenderer *m_renderer; T *m_hPos; T *m_hVel; float *m_hColor; private: NBodyDemo() : m_nbody(0), m_nbodyCuda(0), m_nbodyCpu(0), m_renderer(0), m_hPos(0), m_hVel(0), m_hColor(0) { } ~NBodyDemo() { if (m_nbodyCpu) { delete m_nbodyCpu; } if (m_nbodyCuda) { delete m_nbodyCuda; } if (m_hPos) { delete [] m_hPos; } if (m_hVel) { delete [] m_hVel; } if (m_hColor) { delete [] m_hColor; } sdkDeleteTimer(&demoTimer); if (!benchmark && !compareToCPU) delete m_renderer; } void _init(int numBodies, int numDevices, int blockSize, bool bUsePBO, bool useHostMem, bool useCpu) { if (useCpu) { m_nbodyCpu = new BodySystemCPU<T>(numBodies); m_nbody = m_nbodyCpu; m_nbodyCuda = 0; } else { m_nbodyCuda = new BodySystemCUDA<T>(numBodies, numDevices, blockSize, bUsePBO, useHostMem); m_nbody = m_nbodyCuda; m_nbodyCpu = 0; } // allocate host memory m_hPos = new T[numBodies*4]; m_hVel = new T[numBodies*4]; m_hColor = new float[numBodies*4]; m_nbody->setSoftening(activeParams.m_softening); m_nbody->setDamping(activeParams.m_damping); if (useCpu) { sdkCreateTimer(&timer); sdkStartTimer(&timer); } else { checkCudaErrors(cudaEventCreate(&startEvent)); checkCudaErrors(cudaEventCreate(&stopEvent)); checkCudaErrors(cudaEventCreate(&hostMemSyncEvent)); } if (!benchmark && !compareToCPU) { m_renderer = new ParticleRenderer; _resetRenderer(); } sdkCreateTimer(&demoTimer); sdkStartTimer(&demoTimer); } void _reset(int numBodies, NBodyConfig config) { if (tipsyFile == "") { randomizeBodies(config, m_hPos, m_hVel, m_hColor, activeParams.m_clusterScale, activeParams.m_velocityScale, numBodies, true); setArrays(m_hPos, m_hVel); } else { m_nbody->loadTipsyFile(tipsyFile); ::numBodies = m_nbody->getNumBodies(); } } void _resetRenderer() { if (fp64) { float color[4] = { 0.4f, 0.8f, 0.1f, 1.0f}; m_renderer->setBaseColor(color); } else { float color[4] = { 1.0f, 0.6f, 0.3f, 1.0f}; m_renderer->setBaseColor(color); } m_renderer->setColors(m_hColor, m_nbody->getNumBodies()); m_renderer->setSpriteSize(activeParams.m_pointSize); } void _selectDemo(int index) { assert(index < numDemos); activeParams = demoParams[index]; camera_trans[0] = camera_trans_lag[0] = activeParams.m_x; camera_trans[1] = camera_trans_lag[1] = activeParams.m_y; camera_trans[2] = camera_trans_lag[2] = activeParams.m_z; reset(numBodies, NBODY_CONFIG_SHELL); sdkResetTimer(&demoTimer); } bool _compareResults(int numBodies) { assert(m_nbodyCuda); bool passed = true; m_nbody->update(0.001f); { m_nbodyCpu = new BodySystemCPU<T>(numBodies); m_nbodyCpu->setArray(BODYSYSTEM_POSITION, m_hPos); m_nbodyCpu->setArray(BODYSYSTEM_VELOCITY, m_hVel); m_nbodyCpu->update(0.001f); T *cudaPos = m_nbodyCuda->getArray(BODYSYSTEM_POSITION); T *cpuPos = m_nbodyCpu->getArray(BODYSYSTEM_POSITION); T tolerance = 0.0005f; for (int i = 0; i < numBodies; i++) { if (fabs(cpuPos[i] - cudaPos[i]) > tolerance) { passed = false; printf("Error: (host)%f != (device)%f\n", cpuPos[i], cudaPos[i]); } } } if (passed) { printf(" OK\n"); } return passed; } void _runBenchmark(int iterations) { // once without timing to prime the device if (!useCpu) { m_nbody->update(activeParams.m_timestep); } if (useCpu) { sdkCreateTimer(&timer); sdkStartTimer(&timer); } else { checkCudaErrors(cudaEventRecord(startEvent, 0)); } for (int i = 0; i < iterations; ++i) { m_nbody->update(activeParams.m_timestep); } float milliseconds = 0; if (useCpu) { sdkStopTimer(&timer); milliseconds = sdkGetTimerValue(&timer); sdkStartTimer(&timer); } else { checkCudaErrors(cudaEventRecord(stopEvent, 0)); checkCudaErrors(cudaEventSynchronize(stopEvent)); checkCudaErrors(cudaEventElapsedTime(&milliseconds, startEvent, stopEvent)); } double interactionsPerSecond = 0; double gflops = 0; computePerfStats(interactionsPerSecond, gflops, milliseconds, iterations); printf("%d bodies, total time for %d iterations: %.3f ms\n", numBodies, iterations, milliseconds); printf("= %.3f billion interactions per second\n", interactionsPerSecond); printf("= %.3f %s-precision GFLOP/s at %d flops per interaction\n", gflops, (sizeof(T) > 4) ? "double" : "single", flopsPerInteraction); } }; (adsbygoogle = window.adsbygoogle || []).push({}); 最佳答案 NBodyDemo是类模板，因为它在某些成员和函数（例如T或BodySystem<T> *m_nbody;）中使用参数setArrays(const T *pos,...)m_singleton是类型为static的NBodyDemo指针。 “静态”表示它将由具有相同参数T的所有实例共享。template <> NBodyDemo<double> *NBodyDemo<double>::m_singleton = 0;为“ T = double”专业化初始化m_singleton。template <>是声明范围之外的模板所必需的。关于c++ - 该模板是特化的还是声明(或完全其他的东西)？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/57777028/ (adsbygoogle = window.adsbygoogle || []).push({});