創建 LMDB 數據

給個例子，記錄一下

import sys
import numpy as np
import lmdb


caffe_root = '/home/amax/xyc/caffe-master/'
sys.path.insert(0, caffe_root + 'python')
import caffe

N = 40

X = np.zeros((N, 3, 32, 32), dtype=np.uint8)
y = np.zeros(N, dtype=np.int64)


map_size = X.nbytes * 10

env = lmdb.open('mylmdb', map_size=map_size)

with env.begin(write=True) as txn:
    # txn is a Transaction object
    for i in range(N):
        datum = caffe.proto.caffe_pb2.Datum()
        datum.channels = X.shape[1]
        datum.height = X.shape[2]
        datum.width = X.shape[3]
        datum.data = X[i].tobytes()  # or .tostring() if numpy < 1.9
        datum.label = int(y[i])
        str_id = '{:08}'.format(i)

        # The encode is only essential in Python 3
        txn.put(str_id.encode('ascii'), datum.SerializeToString())