A method is provided for reducing consumption of a memory in a propagation process for a neural network (NN) having fixed structures for computation order and node data dependency. The memory includes memory segments for allocating to nodes. The method collects, in a NN training iteration, information for each node relating to an allocation, size, and lifetime thereof. The method chooses, responsive to the information, a first node having a maximum memory size relative to remaining nodes, and a second node non-overlapped with the first node lifetime. The method chooses another node non-overlapped with the first node lifetime, responsive to a sum of memory sizes of the second node and the other node not exceeding a first node memory size. The method reallocates a memory segment allocated to the first node to the second node and the other node to be reused by the second node and the other node.