Jump to content

  • Log In with Google      Sign In   
  • Create Account


Member Since 15 Jun 2006
Offline Last Active May 23 2016 08:31 AM

#4869315 C++ Interview Questions

Posted by Katie on 05 October 2011 - 03:20 AM

" the one you know the answer to but the interviewer has wrong"

Frankly, it's amazing how common that is. One of the problems with these things is that all too often they degenerate into an opportunity for interviewers to make themselves feel better. And quite often they're over-reaching their own technical skills.

Fizzbuzz or reverse a string is entirely sufficient to lose the maybe 60% of candidates who actually can't program AT ALL[1]. Anything beyond that is frankly labouring the point; esoteric questions about the C++ spec are boring for everyone concerned and have no relation to work actually done. (It was amazing the amount of interviews I went to as an IT contractor which were all about weird tricky edge cases of C++ exception throwing, but when I actually started work there, the codebase doesn't use exceptions because the developers aren't confident enough at using them. And usually therefore they're banned...)

[1] What I find slightly bonkers is that a substantial number of these candidates actually think they are good developers and are surprised to find themselves struggling. It seems to stem from being in large matrix-managed teams where one can spend many many years being only borderline competent at developing without anyone noticing. The actual output of the team is caused by the work units being regularly and randomly swapped between members until (eventually) they're done by the one or two competent developers. In many industries this is normal working practice[2], and staff can truly believe they're contributing because the work units passed through their hands. Likewise I meet an amazing number of highly experienced OO devs who, on closer inspection, have actually spent many years going to meetings where some OO design got done... not *necessarily* by them.

[2] And the appallingly low productivity is (in a storming bit of double-think) considered normal because... well... software developers just actually aren't very good are they? Well, on average NO, they're not...

#4868370 Fundamentals of Game Programming?

Posted by Katie on 02 October 2011 - 02:29 PM

"Should I be creating a simple, procedural program?"


"or should I be using state/process managers and complex class structures"


#4868314 Choosing a college in London as a Programmer

Posted by Katie on 02 October 2011 - 11:11 AM

They're just called A-levels (A for advanced). Yes, they come with grades of A-F.

There used to be O-levels (O for ordinary), but they were replaced by GCSEs in 1988 {IIRC}.

There are also AS-levels (I didn't know why, but google says "advanced subsidiary"), which you used to do as separate subjects but which are now just the first half of an A-level.

There are also S-levels (S for specialist, I think) which are the next one up from an A-level. If you go to an academic college, it's quite often an option to take an S in some of your A subjects {I did an S in physics. Badly.}. S-levels are graded in numbers; there may only be something like 1,2 and U grades for them.

#4868071 Terrain multitexturing problem

Posted by Katie on 01 October 2011 - 02:36 PM

"Is it could be done by multipass? Use depth function to set equal for second pass?"

Yes, this is typically how it would be done.

Make sure you write solidly for the first pass (to populate the depth buffer), turn off depth writing for the subsequent passes (for speed), set equal as the test and then use chained texture blend units to feed the R G or B component from one stage as the alpha into the second.

The key phrase to look up here is "texture combiners".

Basically if you imagine the fixed functionality has a bunch of little units in it which can have the inputs fed from selections of different things -- constant colours, a texture lookup, the glColor or (crucially here) the output from one of the earlier stages.

Setting them up is faffy and fiddly and involves a big stack of glTexEnvi(GL_TEXTURE_ENV,...) calls; it's a good idea to plan out carefully what needs setting up before starting to write the code.

You'll need to do some jiggery pokery with the texture coordinate scales; because one of your textures is big (landscape sized) and one of them is the grass/sand/rock tile. I *think* you do this by chosing the active texture unit and then manipulating the texture matrix, and it'll apply to just that unit. So you can put a scaling on one of the lookups.

You could I guess, possibly do this in one go. Maybe. You'd have to look really carefully at the texture combiner modes available.

Is there any reason why you can't just do this in a modern vertex shader? It seems a lot of work to go to to do this ye olde fashionedey wayey.

#4868068 Choosing a college in London as a Programmer

Posted by Katie on 01 October 2011 - 02:18 PM

If you want to go to university to do computer science or a related course, you'll need to be doing A levels of suitable types. Maths is a MUST. The double maths (maths and "further maths") is good. More science subjects are good. I personally did maths, computing, physics and electronics. Those sorts of subjects are good for compsci entry.

Don't bother doing general studies, it's just wasting time. Steer clear of what are regarded as "soft" subjects. "Media studies" for example being one. Likewise English Lit is useful if you're about to embark on a degree in English Lit, but CS depts will bin your application.

Good news time; compsci courses aren't very oversubscribed!! In other words; good A level grades and you're sorted. No need to be captain of the rugby team and play the lute and also walk on water to differentiate yourself like if you were applying for a "afternoon lectures only" subject like (say) English Lit.

Here is an example of ICL's entry policy; http://www3.imperial.ac.uk/computing/teaching/undergraduate/computing/admissions/advice/

Notice they do not require A-level computing, however TBH, it's probably a useful building block.

Similarly, here's Cambridge's equivalent -- http://www.cam.ac.uk/admissions/undergraduate/courses/compsci/requirements.html

Lots of science, lots of maths. Sorry.

Right, now you know that you need to be doing lots of maths, lots of science, you can go look for a suitable college to go to. Generally this will be a "sixth form" college, not a "further education" college. Colleges in the UK tend to be split into two types; sixth forms are more academic the others are "vocational"; they do courses in (for example), hairdressing, beauty therapy, office administration and so on. If the website does a lot of talking about vocational studies, mentions things like RSAs or diplomas or NVQs, they've maybe not got the focus you'll need.

Your school should really have routes into suitable colleges -- So if you pick a set of four or five A-levels that you'd be interested in studying that fit those sorts of entry requirements, they'll be able to point you in the right direction. I know you're in London, but you can't be the FIRST person at the school to aspire to university :-)

You do not really need a masters degree to do well in the IT industry. I know people who have done the BSc/MSc/PhD routes and while they generally have a useful toolbox of exotic maths and reading papers about FTL neutrinos doesn't make them frown as much as it does me, they aren't intrinsically better software engineers. If you're going to do a masters, do an MBA later on in your career -- being both technical AND business savvy is pretty valuable. But you shouldn't be doing that until you've got some time served at the coalface. Also, if you're sneaky about it, you can locate a company to work which will pick up the bill for doing the MBA (which is NOT CHEAP by the way!)

It's not that an MSc/PhD isn't something to do, but do bear in mind that a) slots for people doing them are restricted, b) you'll be a student for longer. Compsci masters and doctorates are not a key to instant success. On the other hand, it's not unknown for master/doctoral projects and groups to suddenly become startup companies and also I've found that people who have done them seem to have larger social networks within the IT industry. I'm unusual, for example, for being a mere grad still being in fairly close contact with a lot of my graduating year. Whereas masters and doctorates people seem to be more connected. That DOES help with employability, but if you know about this upfront, you can do it without spending five years longer eating pot noodle.

#4863252 Jump thunk table?

Posted by Katie on 19 September 2011 - 01:36 AM

It's just a table of jumps to code which actually does the work. The point being that code outside the module can just call to well-known entry points. Those entry points are jumps to the real routines. The real routines can move around in different versions of the library and the user code doesn't need to be relinked.

#4862701 Windows OpenGL and choosing from multiple video cards

Posted by Katie on 17 September 2011 - 01:19 AM

Aren't you supposed to do this by calling EnumDisplayDevices to get the list of video cards and then using CreateDC to create HDCs on those devices? Then you can use wglChoosePixelFormat (which takes the HDC) to get a render context of the right type on the right device?

#4861419 what is a practical use for the determinant of a matrix?

Posted by Katie on 14 September 2011 - 01:40 AM

If you're working in 3D and using 4x4 matricies as transforms, the determinant has an immediately useful value.

If you put a unit cube through the transform, then the determinant will tell you what the volume of the output cube will be; in other words it tells you the volume scaling that the matrix will do.

Hence, well behaved 3D transforms will all have positive non-zero dets; and all rotation/translations which you expect to do no scaling will have a det of 1.

This also helps explain why zero det matricies can't be inverted. In order for it to have det zero, it must shrink one of your unit cube dimensions to zero. Hence there can't be a matrix which goes the other way, because there's no way to reinflate that deleted dimension back to one. Hence there's no inverse for the matrix.

Obviously, since you HAVE to squash one of the dimensions away to go from the 3D world to the 2D render plane, this means all projection matricies must have det = 0. And hence, this is why there is no general case system for taking a pixel in the window and finding it's location in 3D space, because that would amount to being able to invert your projection matrix.

#4861271 How long until c++ disapear from game development

Posted by Katie on 13 September 2011 - 03:43 PM

" I remember reading an article in Dr Dobbs years ago about how REXX was going to make all programmers obsolete"

I remember reading adverts in the 1990s for the languages which would replace C and C++ with languages so easy that managers would be able to write the code themselves... I'll bet no-one's ever heard of any of them these days.

Easily 20 years this conversation's been going.

It's actually getting very very hard to hire good C/C++ people. And that's a problem because Google runs on hardcore C++ stuff; KVM and Xen need good C hackers, performance libraries for Android need C and C++ coders... Just this week Google is talking about tech to run C++ code natively inside sandboxes because they know the world isn't replacing that stuff any time soon. Good. Means my pay will go up for my rarity value...

We've all been waiting 50 years for Cobol to die and it still won't.

#4857146 How to Log and stay Modular

Posted by Katie on 03 September 2011 - 08:02 AM

" but globals are bad right?"

No, they're not. They're bad if you're an academic computer scientist. Academic computer scientists never actually have to ship code. Globals work, use what works, ship code.

"really messes up my goal of keeping things modular."

Don't have a goal of being modular. Have a goal of "shipping code". What value to you is "being modular"? None. It's an **ideal**. It's not a goal. Your goal is to ship code. That means you get to sacrifice ideals sometimes. This could be one of those times.

You're over-thinking this problem. Everyone always does. Everyone thinks there's a problem with "logging" because it's always either too verbose or not verbose enough and it's never quite right and everyone thinks the way to fix it is to somehow make the logging production more complication.

The problem isn't with the logging. It's with the tool on the other end. Make your program be either "verbose" or "succinct" based on a flag. That's all you need on that front.

Then just output strings but have smarter tools looking at the output.

The UNIX world manages to handle tons and tons of logging using "syslog" which is hardly sophisticated. "syslogd", the program on the other end, that has versions which'll do everything up to handling global networks with millions of servers...

Don't try and solve your logging analysis problems during your log generation.

#4855941 Sprite class and memory effeciency

Posted by Katie on 31 August 2011 - 10:07 AM

Oooooh. Interesting. Maybe there's a reputation threshold?

#4850257 What is the fastes way to load textures in opengl ?

Posted by Katie on 17 August 2011 - 05:39 AM

Instead of using an actual image format (such as TGA) which supports BGRA format, why not ship your images as plain image files already in that format. You don't need all the headers, you just need four bytes per pixel.

Lay them all out in a big block of ram, save that to disk, gzip it. When you come time to load it, you're only loading one file -- you hoof it into one giant block of ram (only 1 allocation, only 1 directory walk). Ungzipping a file is pretty easy on loading it. In addition your compression should be even better; larger files generally compress better than a set of smaller files because the compression can find more similarities to reduce.

Instead of generating the mipmaps on load every time, generate them on first run and save them out to disk. Again, do this one big block if possible. On load, pull it in, rattle down it transmitting the mipmap levels individually.

If you're on an OS which supports mapping the files, you don't need to load them or do an actual memory allocation. Map the file into your address space, provide suitable "linear access" hints to your buffer caching system so it will do read-aheads, start accessing the memory and away you go. The OS will try and load pages ahead of your accesses in the background; you don't have to wait for the "read()" call to complete. The effect of this is that you can already be generating and uploading mipmaps for texture 1 while the disk IO channels are still loading texture 20.

Instead of asking the GLU library to generate your mipmaps, you could build them yourself by using rendering of the fullsize image to pixel buffer objects and copies internal to the card to make them. That way the mipmap data doesn't have to transit the host-GPU bus.

#4850020 Best library for doing text in OpenGL

Posted by Katie on 16 August 2011 - 02:15 PM

Pango/Cairo. Drop it on a texture. Draw it to your screen. Cross platform. Renders everything from plain text up to simple HTML markup. Handles i18n. Everyone always ignores this recommendation without trying it I don't know why.

#4848968 Socket automatically closes after recv

Posted by Katie on 14 August 2011 - 08:18 AM

OK, can you use telnet as a client? Because we know telnet won't close the connection unexpectedly -- so this will find out if the problem is with the server or the client part of the connection.

#4848172 3 years professional experience?

Posted by Katie on 12 August 2011 - 05:41 AM

Send them CVs any way. Make sure you have a good demo. Games companies often don't advertise junior roles -- they have a queue of people already waiting to join them.

Go to job fairs, talk to people there.

Find the developers, talk to them in the pub.

Get recommended by friend who already works there.

Join to do something other than development -- retaining good testers is a nightmare and most companies are always looking for more.