move align.py to psi_demo

python/paddle_fl/mpc/examples/data_alignment/README.md

-## Data Alignment
-
-### 1. Introduction
-
-Data alignment is used for alignment of data set owned by multi parties without leaking any privacy information of data. Concretely, all data of data owners are numbered the same number for the same data. When align, all data owners input the set of data number and get a set of number for the intersection.
-
-
-
-### 2. Example
-
-Here is an example for data alignment between two parties. The `align.py` is a script used for  each party. The set of data number of the two parties are saved in `data_0.txt` and `data_1.txt` respectively. You can directly run `run.sh` for running this example in single machine.
-

python/paddle_fl/mpc/examples/data_alignment/data_0.txt

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python/paddle_fl/mpc/examples/data_alignment/data_1.txt

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python/paddle_fl/mpc/examples/data_alignment/run.sh

-#!/bin/bash
-ENDPOINTS=0:127.0.0.1:11111,1:127.0.0.1:22222
-
-python align.py --party_id=0 --endpoints=$ENDPOINTS --data_file=data_0.txt 2>&1 >/dev/null &
-
-python align.py --party_id=1 --endpoints=$ENDPOINTS --data_file=data_1.txt --is_receiver

python/paddle_fl/mpc/examples/psi_demo/README.md

+## Data Alignment Tool
+
+This is an example of using the `alignment` function to build a command line tool of PSI (Private Set Intersection).
+
+### Usage
+
+```bash
+python align.py --party_id=$PARTY_ID --endpoints=$END_POINTS --data_file=$FILE_NAME [--is_receiver]
+```  
+### Example
+
+Take data alignment between two parties , e.g., Alice (whose party_id is 0, IP address is 'A.A.A.A', port is 11111) and Bob (whose party_id is 1, IP address is 'B.B.B.B', port is 22222), as an example. Alice and Bob would like to find the intersection of alice_data.txt and bob_data.txt respectively, and Bob is intended to receive the final result. 
+
+On each party:
+
+*  **Alice**
+
+```bash
+python align.py --party_id=0 --endpoints=0:A.A.A.A:11111,1:B.B.B.B:22222 --data_file=alice_data.txt
+```
+
+*  **Bob**
+
+```bash
+python align.py --party_id=1 --endpoints=0:A.A.A.A:11111,1:B.B.B.B:22222 --data_file=bob_data.txt --is_receiver