Tensorflow record 1. Download Tensorflow 2. Create a simple model

3. Training The primary use case is to automatically save checkpoints during and at the end of training. This way you can use a trained model without having to retrain it, or pick-up training where you left of—in case the training process was interrupted. …


Kafka is a distributed publish-subscribe messaging system. Publish-subscribe refers to a pattern of communication in distributed systems where the producers/publishers of data produce data categorized in different classes without any knowledge of how the data will be used by the subscribers. The consumers/subscribers can express interest in specific classes of data and receive only those …


ARIMA, Autoregressive Integrated Moving Average Model


Advantage: Easy.

1. Time series or after differencing must be stationary.
2. Only linear relationship.

stationary means now trend, no seasonality.

p–lags Auto-Regressive
d–n differ can be stationary. Integrated
q–lags of error Moving Average


1.synchronized & asynchronized

To share final variable in multiple threads, must use synchronized or volatile.

2. mutual exclusion or visibility
mutual exclusion: only one thread can hold a lock at a time.
visibility: make sure the later thread can see the former thread changes to data.

Atom operation might not be thread safe.
thread can save duplicates of variable in itself memory.

Eight Queen

Eight Queen Problem

This idea is from https://www.cnblogs.com/bigmoyan/p/4521683.html. It greatly reduces the space complexity compare to any 2D array solution.