Simple bank simulation
Optional assignment for higher grade (1 point)
This is a new 1 point higher grade assignment replacing the N Thread barrier assignment.
In this higher grade assignment you will do a simple simulation of money transfers between bank accounts.
Git pull
In order to get the new source files and the updated Makefile for this new
assignment, you need to pull the updates from the GitHub repo.
git pullOverview
In the higher-grade/src directory you find the following files.
- bank.h
- Header file with the API of the simple bank.
- bank.c
- The implementation of the bank API.
- bank_test.c
- A program testing the implemented bank API.
The bank API
The simple bank API is defined in bank.h.
A single bank account is represented by the following C structure.
typedef struct {
int balance;
} account_t;What more is needed to be added to the structure?
- One ore more pthread mutex locks?
- Anything else?
These are the functions in the simple bank API.
/**
* account_new()
* Creates a new bank account.
*
* balance
* The initial balance for the new account.
*
* NOTE: You may need to add more parameters.
*
*/
account_t* account_new(unsigned int balance);
/**
* account_destroy()
* Destroys a bank account, freeing the resources it might hold.
*
* account:
* Pointer to a bank account.
*
*/
void account_destroy(account_t* account);
/**
* transfer()
* Attempts to transfer money from one account to another.
*
* amount:
* Amount to transfer.
*
* from:
* The account to transfer money from. Money should only be transferred if
* thee are sufficient funds.
*
* to:
* The account to transfer the money to.
*
* return value:
* Return -1 if not sufficient funds in the from account. Otherwise returns 0.
*
*/
int transfer(int amount, account_t* from, account_t* to);Add synchronization
You must add the needed synchronization.
Prevent deadlocks
You must make sure to prevent deadlocks.
Pthread mutex locks
This is an example of how you can declare and initialize a Pthread mutex lock.
pthread_mutex_t mutex;
if (pthread_mutex_init(&mutex, NULL) < 0) {
perror("Init mutex lock");
exit(EXIT_FAILURE);
}Testing the bank API implementation
In bank_test.c you find a working program testing your implementation.
Compile and run the test of the simple bank API.
Compile:
make, and run the test program:
./bin/bank_testExample of correct synchronization
This is an example showing two rounds of correct synchronization.
Account Amount
------------------
0 500
1 0
2 0
3 200
4 0
5 0
6 0
7 0
8 0
9 0
------------------
Sum: 700
Round 1 of 100
From Amount To Result
7 ---- 200 ---> 8 Insufficient funds
1 ---- 200 ---> 7 Insufficient funds
2 ---- 200 ---> 7 Insufficient funds
0 ---- 150 ---> 4 Ok
3 ---- 200 ---> 0 Ok
Account Amount
------------------
0 550
1 0
2 0
3 0
4 150
5 0
6 0
7 0
8 0
9 0
------------------
Sum: 700
Total amount of money was initially 700 and is now 700.
System invariant (conservation of money) not broken.Example of incorrect synchronization
In this example, everything looks ok in round 4, but in round 5 a race condition is detected.
Round 4 of 100
From Amount To Result
8 ---- 050 ---> 3 Insufficient funds
1 ---- 200 ---> 7 Insufficient funds
4 ---- 100 ---> 6 Insufficient funds
2 ---- 150 ---> 6 Insufficient funds
4 ---- 150 ---> 7 Insufficient funds
Account Amount
------------------
0 500
1 50
2 0
3 50
4 0
5 0
6 100
7 0
8 0
9 0
------------------
Sum: 700
Total amount of money was initially 700 and is now 700.
System invariant (conservation of money) not broken.
Round 5 of 100
From Amount To Result
4 ---- 250 ---> 9 Insufficient funds
9 ---- 150 ---> 3 Insufficient funds
8 ---- 100 ---> 0 Insufficient funds
0 ---- 100 ---> 5 Ok
0 ---- 100 ---> 9 Ok
Account Amount
------------------
0 400
1 50
2 0
3 50
4 0
5 100
6 100
7 0
8 0
9 100
------------------
Sum: 800
Total amount of money was initially 700 and is now 800.
RACE CONDITION: System invariant (conservation of money) broken!Deadlock
You must make sure the simulation never deadlocks. If a deadlock occur, the simulation will halt, for example like this.
Round 57 of 100
From Amount To Result
1 ---- 250 ---> 7 Insufficient funds
6 ---- 150 ---> 3 Insufficient funds
6 ---- 100 ---> 3 Insufficient funds
9 ---- 100 ---> 7 Insufficient funds
8 ---- 100 ---> 5 Ok
Account Amount
------------------
0 50
1 50
2 50
3 50
4 0
5 100
6 0
7 100
8 300
9 0
------------------
Sum: 700
Total amount of money was initially 700 and is now 700.
System invariant (conservation of money) not broken.
Round 58 of 100
From Amount To Result
0 ---- 200 ---> 1 Insufficient funds
2 ---- 050 ---> 7 Ok
3 ---- 200 ---> 7 Insufficient funds