Ask HN: What are the best optimizations you have made?

https://news.ycombinator.com/item?id=6912874

by elwell • 13 years ago

9 12 13 years ago

news.ycombinator.com

I recently added an index to a relatively large MySQL table that made a certain function go from taking about 15 seconds to less than 0.1 seconds.

penguinlinux• 13 years ago

Tweaked the caching layer for one of the busiest technology media site on the Internet. using only 2 varnish servers I was able to front millions of hits to 5 web back end nodes running wordpress. The configuration for varnish was tweaked so good that we even considered dropping Akamai.

sdogruyol• 13 years ago

Just yesterday i made 2 slow MySQL queries perform nearly 100x faster by replacing the reckless JOINs with smart subqueries.

agibsonccc• 13 years ago

Change my matrix library to a BLAS binding for machine learning. 150x speedup

kranner• 13 years ago

Replaced a naïve very large chart-drawing function in an iOS app with an implementation that uses CATiledLayer.

bret_maverick• 13 years ago

Rewrote a process which took 6 hours to finish to a process which takes 1 minute to finish by using some basic data structures (like a tree).

mattwritescode• 13 years ago

SQL server, query taking 24 minutes to run on a good day, when going down hill wind assisted.

Made a few small alterations and got the query running in sub 1 second. Boss had to have the code vetted 3 times because he could not believe it.

You have to take into consideration that it was originally written by an absolute muppet, and then altered by an `database expert`.

tsahyt• 13 years ago

No specific examples, but all of my best optimizations as in biggest-speedup were of algorithmic nature that actually improved asymptotic complexity.

In terms of my favorite ones, it's probably a piece of C code using SSE intrinsics to speed up intersection checking for a voxel raytracer I've been playing with last summer. After about 1.5 days of hacking I've managed to shave about 50% off the rendering time per frame. Nice learning experience but completely pointless in the end. Since it was still way too slow for any practical use, I started rewriting it and eventually stopped halfway through.

mrlyc• 13 years ago

The best optimisation I made was rewriting 2,650 lines of C as a seven line shell script. The previous programming team had written a data transfer program with its own implementation of ftp. I just used the one that was already on the computer.

iSloth• 13 years ago

I worked for a hosting company doing loads of boring provisioning stuff on servers and the core network, not really a fan of repetition so I started to slowly learn coding and replaced probably 80% of the jobs with scripts. So in total I coded away most of my daily work, although there was plenty more to be getting on with ;)

wikwocket• 13 years ago

Always love stories like this. I never realized the truth of the expression "Go away or I will replace you with a very small shell script" until I started writing shell scripts!

Stories like this can be inspirational, and they reinforce one of my favorite mottoes about computing: "Computers should work; people should think." Have the machines do the rote calculations, and free people to work on challenging creative tasks.

professorTuring• 13 years ago

I have changed the terrible workflow of the team I'm into. This is a group of developers which development process was the following for more than 15 years:

1. Programming with ultra-edit or similar on windows.

2. Never use a library (like STL, boost, libxml, qt...). Big "not invented here" problem.

3. Never thinking about design. Just getting the work done quick and dirty.

4. Copying the code to a remote Linux machine and compile with aged make scripts nobody understands.

5. Go through the whole development cycle without making a commit.

6. Integrate the set of changes from different developers (a huge task in this stage).

7. Not keeping track of bugs or tasks.

8. One meeting each 3 or 4 months.

It has been a job of years (I'm just one more into the team, I'm not the manager and I am the youngest and the last to arrive). I have completely changed their mentality about the development, now they:

1. use a modern I.D.E. (eclipse and qt creator).

2. use an automated tool to sync their code against the remote machine (winscp).

3. commit changes everyday and they integrate all changes everyday.

4. use Trac to keep tracking of the issues and milestones.

5. are starting to use the STL and they are willing to learn Qt and boost.

6. are using Jenkins to automate the compiling and testing process.

7. make code reviews and sometimes pair programming.

8. We meet every two weeks to discuss the status of the project.

The question may be: how I made it?

Like two years ago I asked my boss to be the responsible for the configuration management (a part of the enterprise had already implemented good development practices, but in this enterprise my team is like an independent republic). So I wrote some practices that I believed fitted the team and begin to apply them one at a time. I was very flexible about them (anyway I don't have the power to force my mates apply them).

Later I talked to my boss again and I told her that I wanted to take more responsibility into the team, I told her that I consider myself a great developer and that I was being given only small tasks to make with the team or big projects to do by myself. She acknowledged and gave me the biggest project (in which I'm currently working). With this project I took my chances and began a big refactorization of the old code (believe it is bad as hell). I could add some design patterns and explain them a few more, add some libraries... I know they trust me now much more than before but also they think I am a bit burdensome with all these changes...

Not everything is shiny and colorful anyways. My boss got promoted with more responsibility and one of my team colleagues got the promotion to lead the team (the organization is very big and old fashioned I had not even a chance to get the promotion, before giving it to me all of my colleagues should be retired).

I am very proud of myself achieving this great change into this big and slow enterprise, this change in the mentality of my coworkers. And I do have been rewarded with salary raises. I have greatly boosted the productivity of the team.

I consider there is still a lot to do [my coworkers should be trained better to do their everyday work (improve their c++ skills, they OO design ability, get to know more tools...), add development metrics, static testing tools... ], but it is a bit frustrating and difficult continuing making changes without the "manager title" and having to fight every battle against my coworkers.

Now I have asked for changing my role inside the enterprise to the Security Team (after finishing my Master Degree in Information Security) where I believe I can improve it in the same way I have improved this team (every department has bad relations with the security team because the manager is very theoretical and un-pragmatic) so I am sure I will be handy.

Or maybe I will find a CTO or CISO position in an startup =)

Edited: grammar and typos...

Since English is not my mother tongue any corrections are appreciated.

japhyr• 13 years ago

I take written notes in staff meetings when I see the same shit being discussed over and over again.

When the subject comes up again I say, "We've been through this before. Does anyone have anything new to add?"

Then we either pick up where we left off, or move on to more important issues.

Ask HN: What are the best optimizations you have made?

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