The document discusses code efficiency and provides tips for improving efficiency in different areas. It recommends first measuring performance to identify actual problems before optimizing. It also suggests profiling code with Terminal tools on Mac to detect issues, avoiding initializing objects in loops, lazy initialization when possible, minimizing disk I/O, and being aware of network latency from requests and responses. Big O notation is also introduced to classify algorithm efficiencies.

1. Code Efficiency
Nur Nachman | nurnachman.wordpress.com |
nurnachman@icloud.com

2. Who am I
Nur Nachman
Software Developer
Tel-Aviv

3. First, do nothing
Because there’s no problem yet

4. Measure
You don’t know what’s the problem until you’ve
measured it

5. Areas of efficiency
Memory
Algorithmic
I/O
Network

6. What you control
In a client-server architecture, you can control
the client and server-side efficiency. Though
you can’t control what's in the middle: cellular
network bandwidth.

7. Easy
Look for easy wins
(It’s not cheating)

8. Profiling with Terminal (mac)
top
ps -p {pid}
lsof -p {pid}
fs_usage {pid}
heap {pid}
leaks {pid}
sysdiagnose {pid}
* {pid} = process id

9. Init in loops
Avoid instantiating objects inside loops

10. Lazy init
Instantiate an object only when it’s required

11. Graph inits
Instantiating some objects means instantiating
a lot of sub-objects that live inside the object

12. Printling
print(now());
doSomethingNonEfficient();
print(now());

13. Big O Notation
O(1) = constant (single action)
O(n) = linear (loop)
O(n^2) = quadratic (nested loops)

14. Minimize disk i/o
Only read/write to disk when needed - it's
intensive

15. Net latency
latency = request + processing + response

16. Thank you!
Nur Nachman | nurnachman.wordpress.com |
nurnachman@icloud.com