20/Jun 2011
By admin
4 min. read
Consider the following piece of code:
void FindFrames(const S* seq, float d, UINT& outFrameA)
{
const UINT n= static_cast<UINT>(seq->fd.size());
outFrameA = 0;
while(outFrameA + 1 < n && seq->fd[outFrameA + 1] < d)
{
++outFrameA;
}
} Looks innocent, right? Well, it was slow enough to show up quite high in the profiler… It might seem surprising at first, but if you’ve done some console programming in the past, you can probably recognized our old foe - load-hit-store here.
9/Jun 2011
By admin
2 min. read
Camorra was a Polish demoscene group. They might have not gained same level recognition as Sunflower/Pulse, but they sure were one of the best squads in the first years of Polish PC scene. Camorra actually won the first Polish PC party - General Probe 1995. Sadly, couldn’t find this winning demo (Gust) anywhere. Let’s start with Gustation then. It’s their 64k intro from CAF 1995, took 2nd place behind Why by Adrar Design:
3/Jun 2011
By admin
5 min. read
Normally, I try to avoid C++ bashing, so trendy nowadays. It is what it is, but we’ve to use it anyway. Today, however I encountered a funny bug that made me wonder a little bit. Consider the following snippet:
10/Apr 2011
By admin
3 min. read
Imagine a situation where you’re debugging some problem and need to set a breakpoint in function that’s called very often from many points in your application (like operator[] in your array class for example). Thing is, you’re only interested in one particular codepath, as that’s where things go wrong, calls from other places are fine. If you simply set a breakpoint in line that interests you, it’ll trigger hundreds of times every frame, making it tricky to find the moment that’s interesting for us.
2/Apr 2011
By admin
3 min. read
This recent tweet: "SomeEnum blah : 8;" Added new enum elements so max value is now >127. GUESS WHAT HAPPENS.
— Fabian Giesen (@rygorous) April 1, 2011 from Ryg reminded me of another old story related to bitfields in C++. Consider the following piece of code:
typedef char BOOL;
...
// Some other file
struct SomeStruct
{
BOOL m_something : 1;
BOOL m_isVisible : 1;
BOOL m_somethingElse : 1;
BOOL m_someOtherStuff : 5;
.
18/Mar 2011
By admin
1 min. read
Remember Cruncher#? That’s my little tool for extracting structure layout information from PDB files. It’s pretty much done and I rarely modify it, but from time to time something irritates me enough to force me to get back to it. Recently I’ve added simple, but useful feature. If you double click member variable, it’ll automatically jump to it’s type definition (if it can find it, it must be another UDT). Example:
2/Mar 2011
By admin
3 min. read
Not sure if it has much sense in the era of Twitter (everyone who’s interested can easily find links there), but let’s try. Some of GDC2k11 proceedings:
Networking for Physics Programmers 2011, Glenn Fiedler (SCEA). PDF version here.
Crash Analysis and Forensic Debugging, Elan Ruskin (Valve).
Normal Offset Shadows, Daniel Holbert (High Moon Studios). Thanks, Ignacio!
NVIDIA Game Technology Theater videos + some slides. Found by Guille.
21/Feb 2011
By admin
5 min. read
As promised, today a little bit about mysterious ‘vector constructor iterator’. Essentially, it’s a function generated by MSVC to initialize arrays of UDTs. Unfortunately, sometimes compiler gets confused and tends to spit out superflous code. Consider the following example, taken almost as-is from certain engine (names hidden/changed to protect innocent):
16/Feb 2011
By admin
2 min. read
Recently, I’ve been looking a little bit what’s taking space in our executables and found an interesting ‘feature’ of MSVC. It has troubles with expanding floating-point constants that rely on another constants (…that rely on another constant, yes it requires 2 levels of indirection to break). Consider the following example:
5/Feb 2011
By admin
1 min. read
As you might know, our CEO is the author of the classic Epic Pinball (coded 100% in assembler, obviously :). I’ve spent long hours playing the original, especially the Deep Sea table. Recently, our company in cooperation with Big Blue Bubble, created an Iphone/Ipad version of this game. I don’t have an Iphone, but played it a little bit at the office and it’s just as entertaining as it was, especially the ‘table feeling’ is really well preserved.
29/Jan 2011
By admin
2 min. read
Been working on some wrappers over data containers allowing to move code to SPU easier recently and found myself in need of a compile-time log2 (for shifts, so integers only). Luckily, it’s pretty straightforward to achieve using some template voodoo and boils down to using fact that log2(x) == log2(x / 2) + 1:
23/Jan 2011
By admin
5 min. read
About a year ago I published a few articles on my experiments with C++ reflection system. It extracts all the type information from PDB files. Nice thing - it’s all automatic and requires none to very little source code changes. One thing I didn’t like was problem with adding metadata to our types/fields. It’s mostly for editing purposes, but wouldn’t it be nice to have at least a help/description string for fields?
31/Dec 2010
By admin
2 min. read
One of my Christmas presents (that I bought myself) was WD TV Live Plus media streamer. I left my projector back in Warsaw (sniff) and I was tired of watching stuff on my 15” laptop. WD TV is a pretty neat little machine, it effortlessly plays every video I throw at it. The only problem I had was that it seemed to struggle with TMPlayer subtitle format which is very popular in Poland for some reason.
28/Dec 2010
By admin
4 min. read
Wouldn’t it be nice to get all four of those with some container type? Sadly, it seems quite tricky. Vector gives the most efficient iteration and pretty good insertion (at tail), but is more problematic when it comes to look-up & removal. Intrusive linked lists are pretty good here, but pointer chasing may hurt during iteration. Hash map falls somewhere in the middle, but again - iteration will most probably be slower than vector (we have to skip over empty buckets).
20/Nov 2010
By admin
2 min. read
On Thursday/Friday we had DIG conference here in London. I was quite surprised there is something like that and even more surprise when I found out it’s actually quite big, with DE & other local companies, local universities, hordes of students and interesting lectures. I come from a country where game development is still considered exotic, not very serious career choice. It’s a refreshing change to participate in gaming event organized with so huge support from the city, with London mayor attending.
14/Nov 2010
By admin
7 min. read
(I’m seriously running out of subtitle ideas). Some years ago I started to toy with an memory tracing/debugging tool idea. First proof-of-concept implementation has been created in few days and while it worked with a very simple test app, it required major overhaul before integrating with any real-world program. Somewhere in February 2008 I had a new version, that proved itself very useful during my adventure with enhanced version of certain PC RPG (as it later turned out, it was by far the most memory stressing project’).
10/Nov 2010
By admin
2 min. read
I encountered an interesting problem today. Consider the following piece of code:
namespace Test
{
struct Lol {};
struct Cat {};
struct Foo
{
virtual void Do(Lol&);
virtual void Do(Cat&);
};
struct Bar : public Foo
{
virtual void Do(Lol&);
void DoSomethingElse()
{
Cat cat;
Do(cat);
}
};
} Question: what happens when you execute Bar::DoSomethingElse?
Answer: nothing, as trying to compile this piece of code will result in the following error: ‘Test::Bar::Do’ : cannot convert parameter 1 from ‘Test::Cat’ to ‘Test::Lol &’.
25/Oct 2010
By admin
2 min. read
Gave tr1::unordered_map a try, it seems to do perfectly average, nothing spectacular, nothing awful, except for predict_grow with 4 byte objects, where it’s almost 10x slower than the next implementation (that’s not an anomaly, it happens every time).
I also found a bug in RDE where I overoptimized it a little bit - could result in a crash when searching for item that’s just been removed. It slowed fetch by about 3%, however later I found a way to remove some branches and sped it up by ~6% again, so final version is even faster.
22/Oct 2010
By admin
8 min. read
Big weekend news were EA releasing some of their codebase source, including parts of EASTL. Given that the original EASTL document has been the main inspiration for my RDE STL experiment, I was very interested in finally seeing the code itself. First impression - it’s still big. It is leaner than STL, but it is a big library. That’s quite understandable if you remember it’s not a local, one studio thing, it’s used by the whole organization.
9/Oct 2010
By admin
4 min. read
Few years ago I wrote a short article about dealing with heap corruptions (buffer over/underruns). I mentioned that even after applying described techniques, the biggest problem with overruns is that they’re detected when memory block is freed, not when the actual corruption happens. Those two moments can be very far apart from each other, which complicates debugging. I described some workarounds, but they were not really anything I’d call a satisfying solution.