The 2nd Monitor

> silver coins known as "sterlings" were issued in the Saxon kingdoms, 240 of them being minted from a pound of silver... Hence, large payments came to be reckoned in "pounds of sterlings," a phrase later shortened

SuperBiasedMan

So the weight is actually where the name came from?

Dan Pantry

it has been in use since at least 400 AD

okay, we lose.

Pounds was known as libra from Roman times.

That's why the symbol is libra

So the romans (and lbs) came first

Mast

10:12 AM

Before the euro, we had the guilders. Also called florins.

SuperBiasedMan

We just had irish pounds :( Not imaginative.

Captain Obvious

1

Q: Find a serial port device through WMI (windows management instrumentation)

The idea here is to be able to find a USB serial port device connected during runtime, thus not knowing its port number, and use it in the application to retrieve information from the device. string comportInfo = string.Empty; using (var entitySearcher = new ManagementObjectSearcher("root\\CIMV...

SuperBiasedMan

Not that we had them for long.

Mast

Those were a couple hundred years old, but not as old as the sterlings IIRC.

Zak

@DanPantry I think that's about when my school was founded

Mast

10:14 AM

I still need to grab myself a decent LINQ book.

Looks like it's everything I've been missing in C++ all those times.

Dan Pantry

@Mast Why do you want a book for LINQ?

Its pretty simple stuff

Mast

I got the basics down. But I think it can do way more than I'm currently aware of.

Dan Pantry

LINQ is not that impressive. It's just higher order functions that are deferred until you enumerate the collection

If you want to read about something that needs a book (and is similar to LINQ): introtorx.com

Rx takes the higher-order functional style of LINQ one step further

Mast

Hmmm, looks good and complicated.

Dan Pantry

:D

Dan Pantry

10:30 AM

class redditor{
    Boolean isCool;
    redditor(Boolean isCool){
        this.isCool = isCool;
        theGate();
    }
    private void theGate(){
        if(this.isCool){
            System.exit();
        }
    }
}

I know this was joke code on reddit, but my god, there is so much wrong with this that I don't know where to start.

Captain Obvious

0

Q: Balancing extra backslashes while using preg_quote along with preg_replace

This is my first question on Code review, so please be lenient. I have a user defined expression like this - {geo} == "23.45" Which is evaluated at run-time, after the value of the macro, e.g. {geo} here is replaced. Following is the code I have, currently - $finalQuery = '{geo} == "23.45...

php regex

Jeroen Vannevel

I've got a book on LINQ

It's huge

Also 80% pointless

There are a few functions I could learn more about like .Zip() but aside from that.. They all work pretty much the same and once you understand deferred execution, you know most of its internals

There's interesting performance considerations to be made that require deeper LINQ knowledge though

One day I'll read the book and see if it handles those

Duga

too much / more a case for Code Review. Also not safe: someThing.addAll(SynchronizedSet) iterates over the set. And that needs external synchronization i.e. sychnronized(nextPageQueue). And you will have super high CPU load because you're constantly trying to empty that list. That's what blocking queues are for. — zapl 50 secs ago

Dan Pantry

@JeroenVannevel Yeah, LINQ makes it very very easy to write O(n^P) without realising it lol

~~(Where P is a polynomial obviously)~~ I don't know maths.

Polynomial = n^power + n. power is exponent, not polynomial. HURR DURR

I need to learn comp sci:\

Time complexity

In computer science, the time complexity of an algorithm quantifies the amount of time taken by an algorithm to run as a function of the length of the string representing the input. The time complexity of an algorithm is commonly expressed using big O notation, which excludes coefficients and lower order terms. When expressed this way, the time complexity is said to be described asymptotically, i.e., as the input size goes to infinity. For example, if the time required by an algorithm on all inputs of size n is at most 5n3 + 3n for any n (bigger than some n0), the asymptotic time complexity is...

This is in English, just not the English I know. Why can't these concepts be exlpained in basic terms..

Zak

@DanPantry Did you mean simple.wikipedia.org

Dan Pantry

10:37 AM

simple.wikipedia.org/wiki/Time_complexity#Polynomial_time

:(

Mast

@JeroenVannevel Yea, he LINQ I wrote yesterday is awfully slow.

@DanPantry @Zak Feel free to write it :-)

Dan Pantry

@Mast I can't write it, I dont understand time complexity in the first place

At least not to the degree I need to understand algorithms well enough

Mast

@DanPantry Yea, I was linking your message hoping Zak would go for it. Or @JeroenVannevel for that matter.

Dan Pantry

I just know O(n) is okay, O(1) is great, and O(n^p) is the Very Bad Thing

Mast

Somebody.

Zak

10:41 AM

@DanPantry What's to understand? It's just a measure of how (time to execute) changes with respect to (size of input)

Duga

I think moderators can but I would copy paste and adjust for their guidelines in the process: meta.codereview.stackexchange.com/questions/2436/… — zapl 56 secs ago

Mast

@DanPantry That's about as much as I got, yea.

Dan Pantry

@Zak Moreover the different types of time complexity.

Zak

So, n is the size of your input

Dan Pantry

F.e, polynomial time complexitly.

Jeroen Vannevel

10:42 AM

That's not the slow aspect of LINQ. LINQ has a lot of optimizations for that with lazy evaluation and eager-exiting

Dan Pantry

NP problems

etc

Jeroen Vannevel

It's mostly about heap allocations with all the overhead objects it creates

Mast

And there's logarithmics in there.

Zak

O(1) means that it always takes a constant amount of time no matter how big the input

Dan Pantry

@JeroenVannevel Yes, but you can still write O(n^4) easier with LINQ without realisign it - compared to for example writing 4 for loops deep.

@Zak no, I get that, I know what the basic ones are like o 1 o n and on2

Jeroen Vannevel

10:43 AM

@DanPantry fair enough

Dan Pantry

but O(log n) for example

Zak

Okay, do you know how log works?

Jeroen Vannevel

I think (log n) is better than (n)

Dan Pantry

I've only just learned what an asymptote is, so would I be right in assuming that O(log n) isnt' as linear as O(n) but rather takes less time (ish) per element

because log is an asymptotic function (right?)

Jeroen Vannevel

but then there's also (log n * n)

Dan Pantry

10:43 AM

so it never quite reaches n, but gets closer and closer to it

Mast

@DanPantry You never learned tan functions?

Jeroen Vannevel

tangens? I learned those.. 8 years ago

once

Dan Pantry

@Mast We don't learn that (at least in my school) until A Level Maths, which I dropped out of.

Zak

@DanPantry Essentially, log(n) is to n, what n is to n^n

Dan Pantry

Because I had to start working.

all I know is tan is the tangent line to a circle

where it touches the circle at exactly one point

Zak

10:46 AM

basically, log(n) increases exponentially slower as n increases

Mast

tan is the missing key once you've learned what sin and cos are. tan is what finishes the deal

Dan Pantry

@Mast might be worth me learning sin and cosine too then :p

Zak

great example is binary search

Dan Pantry

@Zak so, in a sense, it approaches the limit N slower than linear increases

Jeroen Vannevel

@Zak That's a hard way of saying log(x) is the b in a^b = x

Dan Pantry

10:46 AM

basically O(log n) < O(n) in terms of complexity

Zak

@JeroenVannevel maybe, but I think easier to grasp

Binary search: with 2 nodes, 1 computation

4 nodes, 2 computations

1,024 nodes, 10 computations

1 million nodes, 20 computations

1 billion, 30 computations

Dan Pantry

that went from 2 to 1024 pretty fast.

Zak

nodes =2^n

computations = n

that's what log is (in essence)

Dan Pantry

didnt realise binary trees were that efficient.

Mast

Dan Pantry

10:48 AM

So.. yes, log is an asymptotic function :P

It approaches n in smaller and smaller increments but never quite reaches it

I always imagine asymptotes as reaching the speed of light (because that's where I learned them from)

you can approach the speed of light but never quite hit it because that would require infinite energy

same deal with log?

where n is the speed of light

Zak

not exactly

Dan Pantry

and obviously log can be used to get the approximate exponent of a value

Zak

Dan Pantry

@Zak nailed it

Zak

log(n) is always increasing

and will, eventualy, reach infinity

but it will increase exponentially slower than n

so yeah

O(n) increases linearly, which is fine

O(n^y) is bad

Dan Pantry

10:51 AM

didn't realise logarithms could reach their Nth term

Zak

log(n) < n for n >= 1

Dan Pantry

so logarithms aren't asymptotic, then

Zak

but if n is infinitely large

log(n) can be infinitely large too, just considerably smaller than n

Dan Pantry

What branch of mathematics is this called? I think I should probably learn about it

calculus?

Zak

I guess.

Honestly, just go straight to "Learn logarithms"

And you should be able to grasp it pretty easily

Basically, any kind of n^y is bad, because computation gets less efficient at scale

Dan Pantry

10:54 AM

Yeah, I know that much

Zak

O(n) is okay, because efficiency is constant

Dan Pantry

quadratic time = The Very Bad Thing

that's why you don't (or try to avoid) doing two nested for - like iterating a two-dimensional array

Zak

log(n) is great because efficiency gets exponentially better at scale

@DanPantry yep

Captain Obvious

0

Q: CRUD strongly typed data access

I have a data access class which looks something like below, using CompanyX.DataAccess.CompanyXTableAdapters; namespace CompanyX.DataAccess { public class CompanyXDataAccess { #region Invoice public CompanyX.InvoiceDataTable GetInvoiceByID(int ID) { ...

c# design-patterns sql-server

1

Q: Multithreaded Webcrawler in Java

I am working on a multi-threaded webcrawling program in Java. Each WebCrawler starts at a root page and repeatedly extracts new links and writes them to a database. I have included most of the code below: public class WebCrawler implements Runnable { private ConnectionPool connectionPool; priva...

java multithreading web-scraping

Dan Pantry

hooray computer science

I would join the Compsci SE but I don't think I know enough for them to even want to answer my questions]

Zak

10:55 AM

log(n^n) is, essentially, O(n)

Dan Pantry

They could just tell me to piss off :P

Zak

It's not really, but for practical purposes, they're similar

Dan Pantry

yeah, thats what I thought. Isnt' there a difference though? Otherwise you wouldn't create the log(n^n) notation.

I would imagine the variance is very slight

Zak

log[base n] n^n = n

log [base A] B^C = variable

depending on A, B and C

Dan Pantry

This doesn't actually solve any questions :(

Zak

10:57 AM

just means, in terms of scale

log(n) is one step down

Dan Pantry

unless you mean to say that when you said log(n^n) you actually meant log(n^y)

Zak

N^n is one step up

Dan Pantry

I should probably do some work.. I'll check back in later

Zak

so if something takes O(n) time

something that takes log(n^y) time will be within an order of magnitude of O(n)

log(log(n^[y^z])) same thing

it might be double, or a tenth, or 23 times more/less efficient

but it won't be exponentially different

And the key to making a computation log(n) complex

is to be able to ignore as much of the imput, as quickly as possible

hence binary trees are great because each computation cuts out half of the tree as irrelevant

hi @Polarbear0106

@Polarbear0106 IS there a good reason for posting that here, or is it spam?

Because if it is, delete it before I flag it.

Polarbear0106

it isnt spam

what do you think about the website`?

Zak

11:03 AM

In what sense?

Polarbear0106

the design

SuperBiasedMan

I notice you posted it in multiple random chatrooms. If you're just trying to advertise then yes it is spam.

Zak

@Polarbear0106 If you want a design review / general feedback. Formulate a question and post it somewhere appropriate.

@Polarbear0106 Just throwing up a link in random chatrooms is going to get you all sorts of negative attention

SuperBiasedMan

He's been sent for a time out according to someone in the GameDev.se chat.

skiwi

Monking

Zak

11:09 AM

@skiwi Monking

@SuperBiasedMan I figured it was something like that, but didn't seem like malicious intent so I figured I'd try and communicate first.

skiwi

Wow, someone spoke so unclear over the phone that I thought he was from another country

Zak

hi @FuzzyLogic

chillworld

monking @FuzzyLogic

Fuzzy Logic

hi. just browsing. what's up in here?

SuperBiasedMan

@Zak Yeah, same. But then I saw they'd done the same on 4 other chats without explanation.

Welcome

Zak

11:15 AM

@FuzzyLogic Not much at the moment

SuperBiasedMan

You missed an improvised lecture on time complexity.

Fuzzy Logic

sounds interesting ^_^

Dan Pantry

It was :)

Though I probably won't retain al ot of it I appreciate the info nonetheless

SuperBiasedMan

Just remember O(log(n)) < O(n) < O(n ^ 2), that's my main take away

Dan Pantry

Yup, same

Or condensed further: Binary trees are great

SuperBiasedMan

11:22 AM

But I appreciated hearing an explanation Zak, I think I got it :)

Zak

glad to help :)

The thing to take away is that something being 10,100,1000 times better/worse is insignificant

compared to how that changes when the scale changes

SuperBiasedMan

Indeed. And nested for loops are the devil's work.

Zak

pretty much. Best thing to think about:

"If everything was 10 times bigger/longer/etc.", how much more time would this code take to run?

you want the answer to be 10 or lower

preferably log(10)

10^(# of nested loops) is not a good answer

skiwi

@SuperBiasedMan O(n log n) is also a very improtant one

Fuzzy Logic

Do you actually calculate Big-O? I never have. I'm familiar enough with it though that intuitively, I just tend to know how a function will fit.

SuperBiasedMan

11:27 AM

In most of what I'm doing (at least right now) the primary bottleneck is always bad stuff like reading multi GB JSON files.

skiwi

I'd say that actively investing time in optimization before you run the code is premature optimization

SuperBiasedMan

Stuff that can't be reduced.

Fuzzy Logic

though, I guess if I were an engineer it would matter more, when you have to prove your designs :)

skiwi

But if you know that you are dealing with very bad performance in Big-O terms and you can fix it with no more effort than the naive implementation, then why not?

Dan Pantry

@FuzzyLogic When working with big data, you have to

I work in the largest commercial credit firm in the world. Complexity is important when searching through records.

skiwi

11:29 AM

@DanPantry Doesn't the database (with indexes) handle most of it already?

Dan Pantry

One of our constraints for one of our features is to search potentially billions of records with a query and it must return in under 4 seconds.

Zak

@skiwi Actively optimizing code is usually premature, but just having a general awareness of the complexity you're implementing is IMO, very important

Dan Pantry

@skiwi The tradeoff with indexes is space.

Calculating indexes is expensive - and so are updating them.

With the amount of data we have its getting to the point where it is simply not feasible to index the fields we want.

In that case we use full text searching

Zak

@DanPantry what language(s) do you program in for work? just curious

Dan Pantry

I discussed this issue with Vogel and Mug before, essentially we are going to run into scaling issues down the road - I'm 99% sure of it.

SuperBiasedMan

11:30 AM

Yeah there's premature optimisation but then there's just being mindful of time complexity when you know it will matter.

Dan Pantry

so I'm trying to suggest we pipe records to a separate database like ElasticSearch which is there specifically for full text searching.

skiwi

But can you still reason about Big-O if you are writing things purely in SQL? That's more my worry

Dan Pantry

That does increase redundancy, however if the records are read-only then it doesn't matter as long as they are kept up-to-date.

@Zak Our stack is JavaScript, SQL, C#.NET 4.5

I personally write JavaScript and some C#.

@skiwi our SQL devs don't tend to, but I do think in terms of that when I see their SQL code and any algorithms we do on the server side (for whatever reason, for example, transforming data from 3rd party sources).

It's not premature optimisation when speed is a feature and part of the specification :-)

Zak

Yeah, it's a case of: You should optimise before you start (design / structure) and after you finish (review) but not when actually writing the thing

Dan Pantry

You can't optimise before you start.

But you should plan ahead for reasonable concerns down the road.

Zak

11:34 AM

I mean, designing a structure / system / algorithm / whatever so that it'll run at a required level of time-complexity

Dan Pantry

For example, if you're going to be doing full text searching on literally hundreds of gigabytes of data, it makes sense to use a service like ElasticSearch with redundant read-only copies instead of putting the load of that search on a SQL box with everything else.

That lends you so much better to horizontal scaling than vertical scaling (Which is the root of all evil)

BTW, if I sound like I know what I am talking about, I don't. I'm just good at bluffing.

YMMV.

Zak

@DanPantry You and everybody else in the world :)

Nobody doing anything interesting knows what they're doing

skiwi

@DanPantry But you'd also need to take into account the O-complexities of whatever the database uses to insert, select and delete

Dan Pantry

@skiwi We can reasonably assume those to either be 1) constant or 2) out of our control.

As a result, it doesn't make sense to factor those into any calculations of algorithm efficiency.

SuperBiasedMan

I only started here in January and back then I didnt know a tenth of what I know now

skiwi

11:37 AM

Them being out of control still affects the total O-complexity

Dan Pantry

@skiwi No.

The speed of the database does not affect the time complexity of the algorithm.

skiwi

I'm still confused where you are running the algorithm

Dan Pantry

In the same way that the amount of cache you have in your CPU doesn't affect the complexity of your algorithm.

The time complexity of your algorithm will be the same no matter where you run it

It may take more time to run that algorithm

Based on hardware specs

skiwi

Time complexity is directly linked to the data structures you're using

Dan Pantry

But time complexity doesn't aim to tell you exact time of execution, it aims to tell you the relative time of execution of an algorithm compared to other time complexities.

Fuzzy Logic

11:39 AM

Big-O is used to measure other things besides time isn't it?

Zak

I think skiwi is trying to say that if your algorithm includes functions that are native to the database

then those functions will still affect the time-complexity, even if you have no control over them

Dan Pantry

Of course they will

skiwi

Say in C# you could be storing data in a Set, List or Dictionary or some more sophisticated data structure, but on the database side the data is stored in data structures that offer better time complexities, hence why we use databases over persisting it manually in an application

Dan Pantry

But there's no point us factoring those in, because we can't control the implementation of those.

Zak

Maybe, but you should know what effect they will have

After all, if those functions execute in O(n) time

Dan Pantry

11:41 AM

That's not my job :p my DBAs do all the SQL writing

Zak

then there's no point optimising anything else below that

Dan Pantry

I see your point. I think I might have misunderstood what @Skiwi was saying

@FuzzyLogic Big-O doesnt' give you absolute time measurements per sé, it just tells you how long you can expect -relative to the other complexities - algorithm A will take.

As the set of data scales

So O(n) insertions might be okay for data sets of 10.

Fuzzy Logic

yeah, I know. but it also applies to r/w and cpu load doesn't it?

Dan Pantry

But if you do an O(n) insertion on a data set with 10000 members in... you're in trouble.

Zak

I think the point that's being made is that if you have a definitive number (4 seconds) you have to meet. You should know the general time-complexity of everything your algorithm does/requires. And then once you're within an order-of-magnitude of your required number, things like actual numbers and hardware specs can be enough to push it below the value you need

Dan Pantry

11:45 AM

Yeah, I suppose

either way, I am 99.9999% sure that we are going to go over the 4 second limit

Because the SQL devs eschewed full text searching (despite it being perfect for the job) and are using a normal WHERE with LIKE.

skiwi

Them not taking into consideration your advice seems to be a bad idea...

Dan Pantry

We did initially use full text searching

I'm not sure why they got rid of it.

Maybe it could have been indexing concerns, but you'd have to put an index on each of the searchable columns to achieve reasonable performance anyway

Captain Obvious

0

Q: `r` permutations of `n`

I have written this snippet to find k-permutations of n, i.e. if i have an array of n=3 {0,1,2}, then k=2 permutations will be {{0, 1}, {0, 2}, {1, 0}, {1, 2}, {2, 0}, {2, 1}}. Can somebody review it and help me optimize / reduce its complexity (I don't want to use recursive function): "_getAllP...

javascript

Fuzzy Logic

^^ speaking of Big-O

Dan Pantry

for (; index < input.length; index++) {

oh god

This could be done using a simple .map call :(

would make it a lot neater

I am confused.

OP:

SuperBiasedMan

11:53 AM

for loops that ommitt one of the three statements always look weird to me.

Dan Pantry

> (I don't want to use recursive function):

He then proceeds to use a recursive function?

SuperBiasedMan

I think they're asking to have it refactored to not be recursive.

Dan Pantry

Hm.

Also, his r is never initialised.

SuperBiasedMan

It's an argument of the function

Dan Pantry

@SuperBiasedMan I know, but I would have expected that to have been an optional parameter

Jeroen Vannevel

11:56 AM

^ that's a parameter

SuperBiasedMan

@DanPantry Ah ok. I thought you might have just missed it cause I did at first.

Dan Pantry

same for usedIndicies and allPermutations.

SuperBiasedMan

(also yes, parameter. I'm in Python mode)

Dan Pantry

Both of those sound like variables that are created during the lifetime of the function.

Phrancis

12:20 PM

Monking

Fuzzy Logic

12:32 PM

hi @Phrancis. nice avatar ^_^

Phrancis

Hahah, thanks :)

Captain Obvious

1

Q: Re-sorting an array of integers based on distinct digits from even to odd

My task was to receive an array of integers and then reassemble the array as required: The array size is to be of element index 0 The next element(index 1) has the number of even distinct digits(digits that appear in only one integer input but not the rest). And the next pairs(if any) of elemen...

c++

Jeroen Vannevel

12:55 PM

github.com/stars/manojjsm

I felt special

turns out I'm just one of many

4

Vogel612

1:26 PM

Monking

Zak

In the review queues, under "close as duplicate". It shows the "question" and the "duplicate". Which is the one being VTC'd?

specifically, here

meta.codereview.stackexchange.com/review/close/105

Vogel612

the one with Question marked as active tab is the one VTC'd

at least that's what I'd expect

Captain Obvious

0

Q: Whats the correct approach to deal callbacks in NodeJs?

I'm working on this simple project I can't get my head around callbacks in Nodejs. What I'm trying to do is get some data and display it in a nice format in slack. But before I can do that there are quite a few steps I have to take, which makes it more complicate for me to follow through callback...

javascript node.js callback

Zak

@Vogel612 It's also what I'd expect. But in this case the "question" is 2 years old and asked by @rolfl and the "duplicate" is 2 days old by the guy who's been a bit over-enthusiastic with his tag privileges

Vogel612

meta duplicates are not strictly chronoligical

in general the better question is the dup target

Zak

1:38 PM

I get that, but I'd like to know which one I'm VTCing before I do it

Vogel612

that being said, I'm not sure whether these are even dups, so I skipped..

Heslacher

@Zak If I see this correctly the "Duplicate" is asked 2 days ago and rolfl 6 days ago.

monking @Vogel612 btw

Vogel612

@Heslacher there's two review tasks

Zak

@Heslacher Oh yeah, I keep forgetting how SE displays current-year dates

Now I definitely want to know which one is the one I'm voting on. Not just for this, but for future reference too.

Heslacher

@Vogel612 I see

Zak

1:41 PM

nvm, I did the simple thing I should've thought of. Went to visit the actual questions to see which had open close votes

It's the "question"

Duga

You're really not supposed to ask two questions in one question (since it makes it hard to select the "right" answer if one answer focuses on one and another on the second), but that's somewhat immaterial since neither is appropriate for SO; you should read the TOS for boots.com for 1) and asking for a more elegant solution is more appropriate for code review for 2) — Foon 21 secs ago

Dan Pantry

his arms are heavy
knees weak coffee mug ready
there's bugs in the backlog already
code spaghetti

(its one of those days)

Vogel612

that's not a full metric haiku, is it?

also Haiku aren't our meme...

Dan Pantry

I am no linguist so probably not

Its a play on Eminem's Lose Yourself

Captain Obvious

0

Q: i got feedback from one company that this code is not good. Could you say what is wrong here?

here is example of code public class IndexerV2 implements Indexer{ private static final Logger log = Logger.getLogger(IndexerV2.class.toString()); private List<String[]> list = new ArrayList<>(); /** * only one key/value pair will be stored * if file has more than one key/value pair ...

java

Zak

1:46 PM

His arms are heavy
Knees weak coffee mug ready
Its code spaghetti

That would be a haiku

3

Phrancis

> The title is awful
It's hard to tell what the code does
Here a vote to close

3

Duga

If you were unsure, or only had a hunch, and don't have any real idea whether your suggestion would even work, then you really should not have made this suggestion in a code review, whether you turn out to be correct or not. It's fine to raise the question and discuss whether it might be of benefit to change the order, but surely there are more important things to focus on. The point of code reviews is to educate and motivate, and I think that your suggestion probably did neither. — Gary McGill 14 secs ago

Zak

@Phrancis I would star, but that middle line has one too many syllables. maybe s/It's hard to tell/ I can't tell?

Phrancis

@Zak Hm, too late to edit :(

Zak

Also, s/The title is awful/[Title is awful] or [The title's awful]

If Haiku's are going to be a meme, I think it's important to get the rules straight form the outset :)

Phrancis

1:58 PM

I'm about as good at writing haikus as I am at writing Java; that is to say, not very good.

3

Zak