A savings account is used to store salary/savings in a bank. This is a concurrent object (RAM) based account. For educational purposes only.

withdraw() from an account blocks until the account has the necessary balance. transfer() from an account also blocks until the source account has the necessary balance. Preferred withdrawls are performed, if waiting.

Using 2 separate conditions avoids unnecessary waking up of non-preferred withdrawls when preferred withdrals are present.

Course: Concurrent Data Structures, Monsoon 2020
Taught by: Prof. Govindarajulu Regeti

deposit(k):
1. Acquire common lock.
2. Deposit to account.
3. Signal that account has currency.
4. Release common lock.

withdraw(k, pref):
1. Acquire common lock.
2. Update pending preferred withdrawls.
3. Wait until sufficient balance available.
4. Withdraw from account.
5. If non-zero balance, then signal it.
6. Update pending preferred withdrawls.
7. Release common lock.

transfer(k, from, pref):
1. Withdraw from source account.
2. Deposit to this account.

## OUTPUT
Setting up accounts ...

Starting transfers ...
6: [21] 100 from 3
4: [55] 100 from 5
7: [145] 100 from 1
0: [195] 100 from 9
5: [199] 100 from 6
2: [68] 100 from 8
1: [36] 100 from 6
3: [39] 100 from 0
9: [22] 100 from 3
8: [73] 100 from 2
3: [139] done
0: [195] done
4: [155] done
9: [122] done

Boss donates 1000 to all
5: [1199] done
2: [1068] done
1: [1036] done
8: [1173] done
7: [1245] done
6: [1021] done

See SavingsAccount.java for code, Main.java for test, and repl.it for output.

references

• The Art of Multiprocessor Programming :: Maurice Herlihy, Nir Shavit