目前我正在使用 Python 进行图像检索。在本例中，从图像中提取的关键点和描述符表示为numpy.arrays。形状 (2000, 5) 的第一个和形状 (2000, 128) 的后者。两者都只包含 的值dtype=numpy.float32。
所以，我想知道使用哪种格式来保存我提取的关键点和描述符。即我总是保存 2 个文件：一个用于关键点，一个用于描述符 - 这算作我测量的一步。我比较了pickle, cPickle（协议 0 和 2）和 NumPy 的二进制格式.pny，结果让我很困惑：
我一直认为cPickle应该比pickle模块更快。但特别是协议 0 的加载时间在结果中确实很突出。有人对此有解释吗？是因为我只使用数字数据吗？好像很奇怪...
PS：在我的代码中，我基本上number=1000在每种技术上循环了 1000 次（），最后平均测量的时间：
timer = time.time
print 'npy save...'
t0 = timer()
for i in range(number):
numpy.save(npy_kp_path, kp)
numpy.save(npy_descr_path, descr)
t1 = timer()
results['npy']['save'] = t1 - t0
print 'npy load...'
t0 = timer()
for i in range(number):
kp = numpy.load(npy_kp_path)
descr = numpy.load(npy_descr_path)
t1 = timer()
results['npy']['load'] = t1 - t0
print 'pickle protocol 0 save...'
t0 = timer()
for i in range(number):
with open(pkl0_descr_path, 'wb') as f:
pickle.dump(descr, f, protocol=0)
with open(pkl0_kp_path, 'wb') as f:
pickle.dump(kp, f, protocol=0)
t1 = timer()
results['pkl0']['save'] = t1 - t0
print 'pickle protocol 0 load...'
t0 = timer()
for i in range(number):
with open(pkl0_descr_path, 'rb') as f:
descr = pickle.load(f)
with open(pkl0_kp_path, 'rb') as f:
kp = pickle.load(f)
t1 = timer()
results['pkl0']['load'] = t1 - t0
print 'cPickle protocol 0 save...'
t0 = timer()
for i in range(number):
with open(cpkl0_descr_path, 'wb') as f:
cPickle.dump(descr, f, protocol=0)
with open(cpkl0_kp_path, 'wb') as f:
cPickle.dump(kp, f, protocol=0)
t1 = timer()
results['cpkl0']['save'] = t1 - t0
print 'cPickle protocol 0 load...'
t0 = timer()
for i in range(number):
with open(cpkl0_descr_path, 'rb') as f:
descr = cPickle.load(f)
with open(cpkl0_kp_path, 'rb') as f:
kp = cPickle.load(f)
t1 = timer()
results['cpkl0']['load'] = t1 - t0
print 'pickle highest protocol (2) save...'
t0 = timer()
for i in range(number):
with open(pkl2_descr_path, 'wb') as f:
pickle.dump(descr, f, protocol=pickle.HIGHEST_PROTOCOL)
with open(pkl2_kp_path, 'wb') as f:
pickle.dump(kp, f, protocol=pickle.HIGHEST_PROTOCOL)
t1 = timer()
results['pkl2']['save'] = t1 - t0
print 'pickle highest protocol (2) load...'
t0 = timer()
for i in range(number):
with open(pkl2_descr_path, 'rb') as f:
descr = pickle.load(f)
with open(pkl2_kp_path, 'rb') as f:
kp = pickle.load(f)
t1 = timer()
results['pkl2']['load'] = t1 - t0
print 'cPickle highest protocol (2) save...'
t0 = timer()
for i in range(number):
with open(cpkl2_descr_path, 'wb') as f:
cPickle.dump(descr, f, protocol=cPickle.HIGHEST_PROTOCOL)
with open(cpkl2_kp_path, 'wb') as f:
cPickle.dump(kp, f, protocol=cPickle.HIGHEST_PROTOCOL)
t1 = timer()
results['cpkl2']['save'] = t1 - t0
print 'cPickle highest protocol (2) load...'
t0 = timer()
for i in range(number):
with open(cpkl2_descr_path, 'rb') as f:
descr = cPickle.load(f)
with open(cpkl2_kp_path, 'rb') as f:
kp = cPickle.load(f)
t1 = timer()
results['cpkl2']['load'] = t1 - t0