Comments for Yet Another Eliot Blog

Comment on My Take on Lag Compensation in MW3 by Eliot

Eliot — Mon, 06 Feb 2012 13:01:31 +0000

Thanks for clearing that up. I was focusing on the handicap added to Black Ops and MW3. It was slightly noticeable on Black Ops but I feel its really apparent on MW3. I really appreciate the old school tie into Quake. I will definitely have a read.

Comment on My Take on Lag Compensation in MW3 by Furyhunter

Furyhunter — Fri, 03 Feb 2012 05:29:20 +0000

I’m beginning to think “lag compensation” is a misnomer for this particular problem in the game. The concept of lag compensation, I believe, came around the time of Half-Life. The server keeps a temporary storage of game states from previous server ticks (up to about half a second in the Delagged Quake 3 mod, iirc) and, when calculating hits from guns, it “rewinds” the game state to a point where it compensates for the time it took for the player’s shot to reach the server, using that cache. As a result, the server is calculating the player’s hit close to where it would have appeared on the player’s screen as opposed to when the server heard of the player’s shot.

This kind of compensation was implemented in Call of Duty in as early as the first game, however I can’t be sure which game — all I know is that it exists in CoD2 and beyond. If it wasn’t in the game, it’d be hard as hell to play the game in high latency environments on the console (as is common in matchmaking).

The “lag compensation” put in with Black Ops and MW3 is actually a sort of handicap that the server imposes, and instead of sending the most recent game state deltas, it sends one from a previous point, to create artificial “latency” on the client. The client still has a low “true” latency, but it’s getting data that is older then what is being sent to the other clients. As a result, the client is sending player state data to the server in its “future” where it only sees the past — and other players see the “future” that the lagged player is sending as the present, allowing them to see you before you see them.

This article explains a bit about Quake 3 networking (what CoD is built on), to make it easier to understand just how the deltas might be generated to create the “compensation”. http://trac.bookofhook.com/bookofhook/trac.cgi/wiki/Quake3Networking

Comment on Using the Jackson Maven Plugin by Eliot

Eliot — Wed, 25 Jan 2012 23:31:08 +0000

Hi Joe,

You are right. It should read Using the Jackson Maven Artifact. I think long tail keyword research got the best of me.

Comment on Using the Jackson Maven Plugin by Joe

Joe — Sun, 15 Jan 2012 11:56:17 +0000

Hi,
Thanks for the writeup but I’m not really seeing any jackson plugin here. Maybe you meant to say jackson library? The thing is maven plugins are something very different.
Cheers.

Comment on Jack Human… WTH?!? by Eliot

Eliot — Thu, 12 Jan 2012 13:02:42 +0000

Hi Sadensy,

Which search engine is FireFox’s search set to? You should see an icon to the left of where you type in text for a search. If you hover your mouse over the icon it will tell you what engine you are using.

Comment on Jack Human… WTH?!? by alfiesaden

alfiesaden — Wed, 04 Jan 2012 11:05:01 +0000

hello – is it just me !! can any one explain why when i type in the firefox browser “blog.eliotpearson.com” i get a different site yet whe i type it in google its ok? could this be a bug in my system or is any one else having same probs ?
sadensy

Comment on Project Euler Problem 1 Revisited by Eliot

Eliot — Thu, 15 Dec 2011 16:09:15 +0000

Yes, I posted it on Reddit. You are completely right. Lines 15 – 17 can be:

val ceiling = args.head.toLong
val factors = args.tail.map(s => s.toLong).toList

That is one less val and a great example of using head and tail. Thanks for pointing me in the right direction.:)

Comment on Project Euler Problem 1 Revisited by dbcfd

dbcfd — Thu, 15 Dec 2011 14:34:53 +0000

Not sure if you’ll post this on reddit, but you’ll want to check out List head/tail. That will eliminate your usage of args(0) and argList.slice. ceiling is equivalent to argList.head, while factors becomes argList.tail.map(s=> s.toLong)

Comment on Project Euler Problem 1 by Eliot

Eliot — Thu, 15 Dec 2011 13:23:45 +0000

Very good point brute force is not needed for this one. Thanks for the explanation.

Comment on Project Euler Problem 1 by Xavier

Xavier — Thu, 15 Dec 2011 06:57:58 +0000

Well, you don’t need Scala or any other programming language, good old math can do it for you

solution
= sum of multiples of 3 < 1000
+ sum of multiples of 5 < 1000
- sum of multiples of 15 < 1000 (because multiples of 15 are added twice)

sum of n first numbers = n*(n+1)/2
sum of n first multiples of x = x*n*(n+1)/2

there are 333 multiples of 3 < 1000 (last one is 333 * 3 = 999)
there are 199 multiples of 5 < 1000 (last one is 199 * 5 = 995)
there are 66 multiples of 15 < 1000 (last one is 66 * 15 = 990)

I know that many people with coding skills will try to brute-force every project-euler problems… but some of those problems actually don't need to be brute-forced.