ChallengeWhat does this code do?
time to read 1 min | 29 words
More posts in "Challenge" series:
- (01 Jul 2024) Efficient snapshotable state
- (13 Oct 2023) Fastest node selection metastable error state–answer
- (12 Oct 2023) Fastest node selection metastable error state
- (19 Sep 2023) Spot the bug
- (04 Jan 2023) what does this code print?
- (14 Dec 2022) What does this code print?
- (01 Jul 2022) Find the stack smash bug… – answer
- (30 Jun 2022) Find the stack smash bug…
- (03 Jun 2022) Spot the data corruption
- (06 May 2022) Spot the optimization–solution
- (05 May 2022) Spot the optimization
- (06 Apr 2022) Why is this code broken?
- (16 Dec 2021) Find the slow down–answer
- (15 Dec 2021) Find the slow down
- (03 Nov 2021) The code review bug that gives me nightmares–The fix
- (02 Nov 2021) The code review bug that gives me nightmares–the issue
- (01 Nov 2021) The code review bug that gives me nightmares
- (16 Jun 2021) Detecting livelihood in a distributed cluster
- (21 Apr 2020) Generate matching shard id–answer
- (20 Apr 2020) Generate matching shard id
- (02 Jan 2020) Spot the bug in the stream
- (28 Sep 2018) The loop that leaks–Answer
- (27 Sep 2018) The loop that leaks
- (03 Apr 2018) The invisible concurrency bug–Answer
- (02 Apr 2018) The invisible concurrency bug
- (31 Jan 2018) Find the bug in the fix–answer
- (30 Jan 2018) Find the bug in the fix
- (19 Jan 2017) What does this code do?
- (26 Jul 2016) The race condition in the TCP stack, answer
- (25 Jul 2016) The race condition in the TCP stack
- (28 Apr 2015) What is the meaning of this change?
- (26 Sep 2013) Spot the bug
- (27 May 2013) The problem of locking down tasks…
- (17 Oct 2011) Minimum number of round trips
- (23 Aug 2011) Recent Comments with Future Posts
- (02 Aug 2011) Modifying execution approaches
- (29 Apr 2011) Stop the leaks
- (23 Dec 2010) This code should never hit production
- (17 Dec 2010) Your own ThreadLocal
- (03 Dec 2010) Querying relative information with RavenDB
- (29 Jun 2010) Find the bug
- (23 Jun 2010) Dynamically dynamic
- (28 Apr 2010) What killed the application?
- (19 Mar 2010) What does this code do?
- (04 Mar 2010) Robust enumeration over external code
- (16 Feb 2010) Premature optimization, and all of that…
- (12 Feb 2010) Efficient querying
- (10 Feb 2010) Find the resource leak
- (21 Oct 2009) Can you spot the bug?
- (18 Oct 2009) Why is this wrong?
- (17 Oct 2009) Write the check in comment
- (15 Sep 2009) NH Prof Exporting Reports
- (02 Sep 2009) The lazy loaded inheritance many to one association OR/M conundrum
- (01 Sep 2009) Why isn’t select broken?
- (06 Aug 2009) Find the bug fixes
- (26 May 2009) Find the bug
- (14 May 2009) multi threaded test failure
- (11 May 2009) The regex that doesn’t match
- (24 Mar 2009) probability based selection
- (13 Mar 2009) C# Rewriting
- (18 Feb 2009) write a self extracting program
- (04 Sep 2008) Don't stop with the first DSL abstraction
- (02 Aug 2008) What is the problem?
- (28 Jul 2008) What does this code do?
- (26 Jul 2008) Find the bug fix
- (05 Jul 2008) Find the deadlock
- (03 Jul 2008) Find the bug
- (02 Jul 2008) What is wrong with this code
- (05 Jun 2008) why did the tests fail?
- (27 May 2008) Striving for better syntax
- (13 Apr 2008) calling generics without the generic type
- (12 Apr 2008) The directory tree
- (24 Mar 2008) Find the version
- (21 Jan 2008) Strongly typing weakly typed code
- (28 Jun 2007) Windsor Null Object Dependency Facility
Comments
It looks like a functional language, maybe f# or Clojure returning a list messages
Google tells me that it's Erlang.I can't understand it for the life of me, but It looks like a small server process, maybe doing unnatural acts on processes.
This is Erlang code. I'm not fluent in Erlang, but I think it starts some Erlang processes and delegates handling of messages to one of those services. Every time this process receives a message it delegates the message to the next "child process".
Don't know Erlang either, but I think I spot some syntax errors/typos:
{stop, normal, State ); --> {stop, normal, State }.
an in handle_call() I guess there's a } missing at the end before the dot, as well as a (maybe optional?) comma in terminate() after ... = State.
I might be wrong though.
its lambda expressions in F# I think but am not sure
It is a map/reduce algorithm written using the gen_server behavior from the OTP erlang library.
Wow, so that's THE map/reduce... I'm totally disappointed, after having heard so much about it i expected it to have at least 200 lines of code.
Nice to see Myspace implementation:
http://code.google.com/p/qizmt/
load balancer in erlang code.
Cadet354,
Great! You got it!
Now, how does it work? :-)
init runs Num threads.
handle_call (Msg, From, State) handled asynchronously (gen_server: cast) request.
(Processes, (CurrentIndex +1) rem Num, Num) selects the next thread that will work.
P.S. I apologize for my bad English
Cadet354,
I'll quibble with threads vs. processes, but you are correct.
Yes, lightweight erlang threads, not OS threads.
@Ayende: Is it something that you've built or did you find the code in some other app?
If you built it, for what project do you use it? I am thinking about Erlang course that we've participated one week ago :-)
It was a sample code that I had written in that course.
Using lists:nth in this way is a bad idea. Quadratic behaviour ahoy!
Possible fixes:
1) switch to using arrays or one of the dictionary libraries
2) change your state to keep two lists: the processes you haven't used this round yet, and the ones you have. When the first list runs out, reverse the second and use it again.
Additionally, it's now trivial to add more processes, if desired.
@Oliver
Your first correction is wrong, the other two are right
Comment preview