This post is split out from my main summary of Algorithms to Live By by Brian Christian and Tom Griffiths. Check out that summary to learn more about the book.
Time management books advocate different strategies to prioritise tasks.
Which strategy is ideal depends on your goal
Different strategies optimise for different things. For example:
- Earliest Due Date (starting with the task due first) minimises the lateness of your latest task.
- Moore’s Algorithm (a variation on Earliest Due Date) minimises the number of late tasks.
- Shortest Processing Time (SPT) (doing the quickest tasks first) minimises the amount of time other people waiting on you. Getting Things Done advocates a strategy along these lines — to immediately do any task that takes less than 2 minutes. This strategy also reduces the number of outstanding tasks hanging over you.
Best way to get out of debt? It depends
Two popular debt reduction strategies are:
- Debt avalanche. Pay off highest interest rate debts first and then work your way down the list. This strategy is optimal for reducing your total amount of debt, and corresponds to the Weighted SPT strategy.
- Debt snowball. Pay off the smallest debts first. This is the debt-equivalent of the SPT/Getting Stuff Done strategy of doing every task under 2 minutes first. It reduces your number of debts rather than the total amount, but can minimise hassles like dealing with multiple bills and collection phone calls.
Which strategy is better remains an active controversy in the personal finance space.
Tractability of scheduling problems
Sometimes tasks are blocked by other tasks (“precedence constraints”). Such constraints can make a problem intractable.
Luckily, the ability to switch tasks partway through (aka “pre-emption”) can make an intractable problem tractable. (But beware that context switching comes at a cost, as discussed in my main summary.)
Surprisingly, even uncertainty can help make a problem tractable — knowing the start times and durations of all jobs in advance can make it practically impossible to compute the optimal schedule, while reacting as tasks come in is much easier.
The best scheduling strategy
The best general-purpose scheduling strategy is probably the Weighted SPT with switching. Weighted SPT is like SPT, but accounting for the fact that some tasks may be more important than others.
Here’s how to apply it:
- Calculate the “density” of each task by dividing its importance by the amount of time it takes to complete. In a business context, importance could be a project’s monetary value, and the density could be its hourly rate.
- Start with the high-density tasks and move down the list.
- Each time a new task comes in, compare its density to the one you’re already working on. If the new task’s density is higher, switch to that task. Otherwise, keep working on your current task.