Cluebat-man to the rescue : General

Tech-ed Berlin 2009: Afterthoughts

vanDooren — Mon, 16 Nov 2009 20:47:40 GMT

All in all, tech-ed was worth it this year.

If you’re an an IT professional, then visiting tech-ed is a valuable learning experience. Even though most of my job involves off-the-shelf process control software, this software is still running on the Windows platform, and uses Windows and Microsoft technologies to work.

So for the purpose of administering and troubleshooting software on the windows platform, it is important to know how the software works, what it’s capabilities and configuration options are, and how it fits into the larger ‘Microsoft’ eco system.

By attending tech-ed and choosing the appropriate tracks, it is possible to keep a broad perspective. By knowing the important basic aspects of Windows 2008 and SQL server, Active Directory and other related things, I can get a better understanding, which will always come in handy eventually. Sooner or later we’ll run Windows 2008 and Vista, or ‘7’, or SQL server 2008, or something else.

And some things are downright practical already: The capabilities of powershell are astounding, and can definitely make life much easier in cases where now batch files are used that are not always easy to understand, or unable to provide much feedback when run as a scheduled task.

From that perspective, tech-ed was definitely a success.

Technorati Tags: General,Event,Teched

Installing Windows 7: Defeating the black screen

vanDooren — Mon, 16 Nov 2009 20:32:01 GMT

After tech-ed I am excited about developing for Windows 7, and playing with the parallel computing toolset that is going to be part of Visual Studio 2010. Since my existing partitions were already quite cramped, I thought I’d install 7 on a new disk so that I can put it on a 200 GB partition.

I bought a new 640GB Western Digital disk and set out to install Windows 7. all went fine until after the first reboot, when I got a black screen and my monitor fell in power save. I tried rebooting in safe mode but that didn’t work.

For some reason, Windows 7 can sometimes do something funky to the display settings, causing the video card to turn into a problematic mode.

After some fiddling around, I found out (thanks google) that I can press F8 to start Windows 7, and choose an option to force the video resolution to 640*480 and bot succesfully. I was then able to download the proper nvidia drivers, install them, and configure the proper display settings.

Technorati Tags: General,Windows

VMWare Server 2 Console WTF

vanDooren — Wed, 19 Aug 2009 09:48:00 GMT

I've been using VMWare Server 2 on a Vista 64 host to simulate a network environment for testing our operating procedures. Everything was working fine before I got on holiday. Now I am back for 2 weeks, and suddenly, VMWare thorws a wobbler.

Using the server console, I can start and stop local virtual machines, but whenever I try to connect to the console, I got the following error: 'Error opening the remote virtual machine machinename:8333\16:
An unexplained error occured.'

Brilliant. An error message that is as useless as a bookshelf made from mashed potatoes, that turns up without any changes to the system. And of course, googling did turn up many people with the same problem, but noone with a solution. Eventually, I found someone who suggested a solution for generic connection problems:

On the host computer you need to access the network properties for vmnet1.
find Internet protocol tcp/ip (v4) click properties
in the window use following DNS server address enter the static ip address displayed or enter the ip address 127.0.0.1
hit ok
hit ok again
done ! restart the machine to verify working

I have no idea why this is suddenly necessary, because the machine name is the local name and I can ping it without a problem. And VMWare consoles used to work just fine before my holiday, so I am really a bit annoyed with this. Still, the above fix worked like a charm so I am not going to complain too much.

Long time no see

vanDooren — Mon, 17 Aug 2009 06:53:00 GMT

It's been a while since I blogged here. Lack of inspiration, lack of time, lack of interest... Over the past couple of months, I've been occupied with other stuff.

The guest bathroom needed finishing, and my wife had a number of creative ideas that looked great but also needed a lot of time. I have started doing martial arts again, and I have been practising 2 times per week, so that is another 2 evenings no available for doing tech stuff. And the little time that I had left, I didn;t feel like programming.

But now I am back. I have started participating in the MSDN forums again, and I hope to write some more articles on ATL in the near future, because ATL is just cool.

My registration for tech-ed in Berlin has also been approved last week, so I will be blogging about that in november. Last year I didn't go, so most of the content should be new to me. Too bad they switched from Barcelona to Berlin. Spain can still be very nice in November. Then again, I won't miss the olive oil.

Oh and in case anyone was wondering: I was re-awarded in July, so I'll be an MVP for another year.

The kerberos client received a KRB_AP_ERR_MODIFIED error

vanDooren — Thu, 02 Apr 2009 10:43:00 GMT

This is what I got in the event logs yesterday afternoon:

Event Type: Error
Event Source: Kerberos
Event Category: None
Event ID: 4
Computer: SE-SMURF01
Description:
The kerberos client received a KRB_AP_ERR_MODIFIED error from the server PC-BLABLA09$. The target name used was . This indicates that the password used to encrypt the kerberos service ticket is different than that on the target server. Commonly, this is due to identically named machine accounts in the target realm (FOO.BAR.STRIPE.LOCAL), and the client realm. Please contact your system administrator.

Event Type: Error
Event Source: Kerberos
Event Category: None
Event ID: 4
Computer: SE-SMURF01
Description:
The kerberos client received a KRB_AP_ERR_MODIFIED error from the server PC-BLA09$. The target name used was RPCSS/PC-BLA10. This indicates that the password used to encrypt the kerberos service ticket is different than that on the target server. Commonly, this is due to identically named machine accounts in the target realm (FOO.BAR.STRIPE.LOCAL), and the client realm. Please contact your system administrator.

I had replaced those machines a week ago, and everything seemed to work fine. So I didn't understand why these errors were suddenly popping up. The applications running on those computers where throwing a wobbler as well. Some googling later I found 2 remarks that were useful.

The first one was that someone fixed it by taking the computer out of the domain, renaming it, changing the SID, and changing the IP address. While this is overkill on the scale of killing a mouse with a thermonuclear weapon, it pointed in the direction of a network level problem.

The second remark was by a Microsoft employee who explained that DNS misconfiguration can be the source of problems like this. If kerberos thinks it is communicating with pcA it encrypts the kerb ticket with the password of pcA. but if the ticket then ends up on pcB because of the DNS mismatch, the above events will be logged.

At that moment I realized that I had changed the IP address of an adapter on PC-BLA10 because it conflicted with PC-BLA09. The reason everything worked fine initially was because that port had been left disconnected until 2 days ago when I configured the correct IP address. The conflict was resolved and the DNS information was updated, but that didn't mean that the DNS caches were up to date. So I cleared the DNS cache of the DNS server, and used ipconfig /flushdns to clear the resolver cache on the domain controller and PC-BLA10, and the problem disappeared.

Scheduled task would not run

vanDooren — Wed, 25 Feb 2009 08:13:00 GMT

The scheduled task for running ntbackup on our fileserver would not run anymore. It would stop with a return code of 0x80, and nothing worthwhile in the log file or event log. It ran fine for months, apart from the occasional hickup such as having no more free tapes in the loader, or a tape not being imported correctly.

I tried running the backup batch file manually, and that worked fine. I ran it under the dedicated backup account, and that worked fine too. But it wouldn't run automatically, and starting the task manually when logged in didn't work either. I couldn't find any useful debugging info so I turned to google. I found several people who has similar problems, but most had to do with a bug in the HID service which somehow interfered with ntbackup. I looked around some more and finally I found something that ended up giving me the final clue.

I opened up the task manager and noticed that there were 21 instances of xcopy still running, 23 instances of psexec, and 3 instances of ntbackup. These were probably left over from some tests I had done with the backup script of one of the new servers (a backup domain controller) which uses the 3 aforementioned programs.

After killing these dead processes I tried to run the backup task again, and everything worked fine this time. In my naivety, I had assumed that ending a task would end the processes it had spawned, but that seems to have been a mistake. Ah well, everything is working again, and now that I know the cause, I can prevent this from happening again.

This is why I try to understand a problem, rather than just rebooting the machine. A reboot would have fixed the problem in less time then I needed to figure this out. But then I wouldn't have known what happened (I hate that) and I wouldn't be able to prevent this from happening again. I would have been stuck in a regular but unknown problem -> reboot cycle.

File a bug report and make Visual Studio a better product

vanDooren — Thu, 22 Jan 2009 06:50:00 GMT

If you find a bug in Visual Studio, report it on http://connect.microsoft.com If the bug affects the version of VS that is in development at that time, there is a significant chance it will get fixed before the next release. Just this week I got confirmation that all 3 bugs that I filed in the last months have been resolved.

The first one is a nasty one. If you add an ATL project to an existing, non-empty solution, the ATL wizards will either hang the IDE or fail to work when adding an ATL object. I found a workaround for it, but it involved hand editing the solution file.

The second one is a small bug in the TR1 regex parser. No workaround, other than to restructure the regex.

And the last one was an error in the MSDN documentation about open modes with the fopen family, which counts as a bug because it triggered runtime errors.

All 3 have been fixed. I especially appreciate the first one. I am working on ATL projects, and I develop my COM server in the same solution as a couple of related non-ATL projects. So every time I work with ATL projects, I can have a warm and fuzzy feeling that because of me, VS is now a better product. :)

Cold, Coffee, and Developers

vanDooren — Fri, 09 Jan 2009 07:04:00 GMT

We are going through an unusual spell of cold weather at the moment. It was -15C when I left for work this morning. The intense cold also caused some of the outside water pipes on our site to freeze. In particular, the ones running to the temporary trailers where I am located atm. No water -> no coffee....

Except for me, that is. I have been making my own coffee for a long time now (pouring hot water over a filter with hand ground arabica beans). This means not only am I the only one here drinking good coffee, the last 2 days I was the only one drinking coffee :D.

And I know several peopel whose day did not begin well because of it. But I didn't gloat. Poking fun at people going through caffeine withdrawal is just too dangerous ;)

And for something compeltely different; I read this on Raymond's blog:

Generally speaking, programmers don't do the visual design. I mean, these are people who are lucky if they are wearing matching socks when they come to work, if they even remember to wear socks at all. And you want them to design a color scheme?

I usually manage to wear matching socks, but when it comes to choosing interior decoration, paint colors, curtains and other stuff, my wife is firmly in charge. She has a veto on my clothes too :)

Maybe there are people which are both great developers and great graphics designers. But I'm not one of them, for sure. I prefer command line apps, services, COM servers, drivers, and other low level stuff. I am good with code, not with graphical stuff. The rare few times I need to have a GUI, the best I can come up with is the default grey dialog based application, and a menu if I am feeling creative.

Don't people read anymore before commenting?

vanDooren — Wed, 03 Dec 2008 10:37:00 GMT

Blogs are funny things. We all have different reasons to write blog posts. Apart form the general stuff that almost everybody sometimes writes about (opinion pieces, general comments about something or other) I like writing tech articles.

Programming is my hobby, and sometimes I like to set myself a challenge, or want to see what sort of interesting things I can do with a given API / language / platform. Afterwards, I write an article about what I did, partially because I actually like writing things like that, and partially because you don't know if you understand something fully until you can sucessfully explain it to someone else, leaving out no details.

You'd be amazed about how many things you take for granted until you are forced to explain them step by step. And you'll quickly find out that some things you've never thought about twice were wrong.

Anyway, It takes a lot of time to write a detailed article about something technical (much longer than you'd expect). And I always hope that if you care enough about it to comment on it, you've actually read it. But sadly, I am often disappointed.

Take this article for example. I wrote it as an example of how it is possible to create a fifo queue without locks. In the article I mention that there is 1 writer, and 1 reader, and that my implementation is thread safe, specifically because of that. And after all, this is a simplified proof of concept of something, so lack of advanced features (like signalling) is to be expected.

And yet a lot of people comment the same thing every time 'Your code is wrong, this bit has a race condition. this is a basic mistake' and variations thereof. And then I think to myself 'Yes, of course there is a bloody race condition. That is why I mention that there should be only 1 reader and 1 writer!' What makes it even worse is that a number of people already commented this, and that I've already answered that comment several times.

I am definitely not a prima donna programmer. I never mind explaining something about my code or design, even if I have to do it a couple of times. And I really welcome comments, bugreports and other feedback about my code. If I made a mistake, I'd like to know. But I hate it when people start spewing comments without even bothering to read the article and / or the comments that have already been posted. Is it really that hard not to make an idiot of yourself?

Visual Studio 2008 on Windows 2003

vanDooren — Fri, 21 Nov 2008 20:39:00 GMT

I've had a weird problem on my development station for some time now. Every time I ended a debugging session of a C# project, visual studio froze for about 10 seconds. It also happened if I changed project settings, but I never had any problems with C++ projects.

My development station at work is a DELL Precision 670 running windows 2003 server. It has 2 dual core Xeon cpus, 4 GB of memory, an nvidia 8500 graphics board and a WD sata hard disk. It is fast, so any lags or slowness would not be hardware related.

Now, if I was Mark Russinovich, I would use my extensive debugging experience to track down the underlying problem. But I am not, and since the majority of my work is C++, and I don't start and stop debugging sessions frequently, I could not be bothered to spend a lot of time to hunt down the problem. Installing VS2008 SP1 didn't fix the problem so I suspected it had something to do with my local configuration.

Today I finally figured it out: This was caused by the windows 2003 'Enhanced Internet Security configuration'. Removing that from my system solved the problem and VS2008 was finally as snappy as I'd expect.

I don't know exactly what the problem was, but C# projects do much more with XML and html than C++ projects. I think it is probable that C# projects do something that triggers the security configuration, which then doesn't respond because there is no user to acknowledge a prompt. 10 seconds looks like a reasonable connection timeout, so it is at least plausible.

I still would like to figure out the real cause of the problem, but at least my problem is solved. If you experience anything similar on Windows 2003, it might be worth trying this.

In my case I simply removed the entire Enhanced Internet Security configuration from my system. It is not connected to the internet, so the risk is pretty much nonexistent.

Passed 70-290 today

vanDooren — Fri, 14 Nov 2008 21:48:00 GMT

I have been silent on my blog for the last couple of weeks. This is because I spent all my time preparing for my first Microsoft exam in a couple of years. But it has been worth it. Today I passed the Microsoft certification exam 70-290: Managing and Maintaining a Windows Server 2003 Environment.

As I am really a software developer, cunningly disguished as a sysadmin, I doubted I would make it at the first attempt. But I took a lot of time to prepare, and tested all the topics in a test environment.

Long story short: I aced the exam with a perfect 100% score :)
The lady in the test centre told me that I was only the second to ever ace a Microsoft exam like that in that test centre, and the first outsider. The other guy
worked there as a trainer.

What makes this particular exam score even sweeter is that
a) I only used the MSPress book (no exam cram crap)
b) I pulverized the record high scores of the guys in the ICT department. :D

Definitely a nice way to start the weekend.

Funny picture

vanDooren — Tue, 28 Oct 2008 10:49:00 GMT

One of the forums that I visit daily (well, I am the moderator after all...) has a funny picture thread.

This one made me laugh out loud:

Installing Zune software without internet connection

vanDooren — Fri, 24 Oct 2008 05:42:00 GMT

Last week I bought myself a zune, and since my main computer during the day is my company laptop, I wanted to install it on that one. Unfortunately, going to zune.net didn;t help because the first thing the installer does is to check if Windows Update is enabled. And if it isn't, it aborts. Of course, if you don;t have an internet connection at all, it aborts as well.

My laptop is ruled by company policies, and security is not a laughing matter here. Regardless of what my opinions are, I am not going to tamper with that, since that would be very much a 'Bad Thing (tm)'.

After a lof of googling I discovered that a lot of people have this problem, and the folks at Zune.net seem to think that this situation needs no special attention. Luckily I found the solution on a zune forum. There are lot of alternate approches, but they require some degree of hacking with settings, which I do not want to do.

Download the client package which contains all the files, and not the setup shim you can find on Zune.net
Extract the files
Navigate to the packages folder in x86 folder.
Install wmfdist11-windowsxp-x86-enu.exe
Install windowsxp-kb915865-v11-x86-enu.exe
Install zune-x86.msi
Restart the computer
Connect your Zune and wait for the driver isntallation and device detection

For x64 the setup will be similar, but you won't need the kb patch. It shouldn't be too hard to figure out which files to install if you have an x64 system.

I have to admit I am a bit disappointed by Microsoft and the Zune folks for not explaining this in the FAQ on Zune.net or somewhere else where you can easily find it.

I am not the only one with a corporate laptop and a zune, and many people seem to have had this problem, judging by the number of hits I got.

It seems the Zune decision makers want to force people to be online.

My 2 new kitchen knives

vanDooren — Mon, 20 Oct 2008 06:00:00 GMT

This has been sitting in my drafts folder for a long time, but I finally got around to finishing this blog post. The knife shop in a nearby city held a firesale, and my wife told me I could go and have a look and see if there was anything worth having... I don't what I did to earn this but I wasn't about to complain.

So after some consideration I decided to buy 2 kitchen knives with a 20% discount. Still nowhere near cheap, but not a bad price, and I had wanted to buy good knives for a long time already. The knives we had up until now are cheap made in china items, made from crappy steel, and way to soft to hold a decent edge. These are the kind of knives found in the average household. Honing, hones and staight razors are my main non-programming hobbies, but up until now, good kitchen knives were not on the household priorities list. Blessings be on my wife for being this generous :)

The first one I picked was the Kai Shun dm-0701 general purpose kitchen knife. It's edge is 6 inches long, and it is made from pattern welded steel which was hammered and folded 5 times to end up with 32 layers of steel. Despite being stainless its Rockwell hardness is 61 +-1, which means that it should take and hold a near-razorsharp edge.

The second knife was the Wusthof 4972 Japanese style vegetable knife. It's edge is also 6 inches long, and it is made from high quality stainless steel. It has a Rockwell hardness of 58, which should make it a bit easier to hone. I don't know hat to expect of the edge retention qualities, though they should be OK.

The Kai, with the belgian blue whetstone on the background

The Wusthof, with the yellow coticule in the background.

The good

Both knives are of a very good quality despite being stainless. The Kai factory edge was sharp enough for my taste, which is rare enough. Factory edges cannot be trusted. They might be sharp enough, but there is a variation, and the factory edge is in no way indicative of the quality of the blade.

I already used both knives, and the balance and the feel of them are excellent. I have already fallen in love with the Japanese knife after I used it to cut meat, and I didn't feel any resistance from the meat. I am still undecided on the Wusthof. I have never used that blade style and I still have to get used to it. Atm my bias is positive.

The bad

Not much bad to speak of yet, except that the knives come without detailed information about the steel, and without honing guidelines. To be honest, this is a bit like complaining that the average car does not come with tuning instructions. 99% of the people wouldn't know true sharpness or quality steel if it hit them in the face (it would be a brief experience :D).

Of the remaining 1% who do care, 99% think that honing a knife is no more complicated that drawing it through some e-z-sharp applicance with ceramic discs (shudder...) or whacking it against a steel 'like they do in the movies'.

Only people with a passion for honing or knives will generally really care about the things I mentioned, so I don't hold it against the manufacturers that they don't supply it with the knives. The information was easily accessible on the internet on various kitchen knife blogs.

The ugly

I was pretty disappointed with the sales pitch I got at the shop where I bought those knives. I quickly discovered that I knew more about knives than the sales woman when I asked questions about the steel that was used in the different knives.

Me: Hi, could you tell me a bit about the different types of steel that is used in these knives? Which kinds do you sell?
Her: Huh ????????
Me: Do you have any Japanese carbon steel knives?
Her: Huh ????????
Me: Ok do you have any knives that would rust if I let them stay wet for too long?
Her: Oh no. We don't sell those. Why would anyone want to have such knives. That would be very unhiegenic I would think.

Now, while it is true that carbon steel knives will rust if you leave them wet, they will not do so if you care for them. Stainless steel lets you get away with a lot of abuse, but carbon steel doesn't. A professional chef told me that I'd be appalled at how a lot of restaurants store their knives. Carbon knives can generally take better edges, and force you to care for them.

The verdict

I've had these knives for a couple of months now. After honing them by hand (took awhile to find the best stone and technique to sharpen the wusthof) they are now very sharp, and excellent cutters. Both knives are superb, and welcome additions to my kitchen.

They are different though. The Kai takes the sharpest edge, and is a great pull cutter (i.e. you slice by pulling the knive across or through something) while the Wusthof -due to its shape- is a great push cutter.

Both knives are a joy to use once they are sharp (the wusthof was finicky to get right) and as with all sharp things: keep them safely away from curious kids :)

Windows Instant On

vanDooren — Fri, 17 Oct 2008 09:54:00 GMT

Something I picked up on slashdot today: Microsoft is checking if people would want an 'instant on' version of Windows.

As compelling as it sounds, I don't think it is that big a deal, and they shouldn't waste their time with it. These days, evey computer and laptop supports Standby or Hibernation. Between the 2 of those, there is no reason why Microsoft should invent an 'Instant On' option that is limited in what you can do, if it is perfectly possible to resume from hibernation or standby in the same amount of time and have a fully functional system at your fingertips.

But let's for the moment assume that my computer support neither of those options.

My home laptop is an old P3 1GHz with 700 MB RAM. It is not part of a domain , and is fully usable 15 - 20 seconds after I touch the power button. Instant enough for me. My workstations are the same, only it takes 20 seconds or something like that for the system to POST. So even the instant on feature would not save me from having to wait.

Then there are my machines at work. They are part of an enterprise domain. Booting windows takes a relatively short time. It's only when I log in that the wait begins. The delay before I can actually use my laptop is long enough that I can go to the coffee machine, get hot water and brew my own coffee by manually pouring hot water over a drip filter with hand ground beans. By the time my cup of coffee is full, it can happen that I can access the start menu, though that is not a given. Usually it takes another 5 - 10 minutes before the system has finished doing whatever it needs to do.

The reason of course is that -as in a typical enterprise- there are so many group policies which are refreshed. Then there is the virus scanner that is starting its scan, remote management software (sms) that is started, system checks that are performed, services that are started, ...

So Instant On wouldn't help me much there, because the amount of stuff that is going on would be the same. Of course they could prevent this prom happening, but I am pretty sure that no domain admin wants to allow a computer on the network if it hasn't jumped through all the hoops to make sure that it is compliant with all the policies and limitations that are required by the corporate policies.

It would probably best if they ditch Instant On right now, and start focusing on Windows 7, making it robust and responsive.

Small bug in the MSDN documentation

vanDooren — Thu, 09 Oct 2008 06:02:00 GMT

Hardly worth mentioning, but there is a minor bug in the documentation of fopen and its friends. The remarks section lists the open mode encoding for 16 bit unicode as UTF16-LE instead of UTF-16LE.

As I said it is very minor, but if you use fopen, care about the documentation and have 5 minutes to spare, you can hop over to my bug report on connect and add a vote.

Installing a service pack: how much space do you need.

vanDooren — Tue, 07 Oct 2008 09:57:00 GMT

Yesterday I had to install VS2008 SP1 on a computer with limited disk space on C:\

Even though VS2008 itself was installed on D:\ the installer (which is 800MB) still required 3.3 GB of space on C:\

I molested C: until I had enough space to perform the upgrade, but I felt something was wrong. After some searching it turns out that due to various issues, the rule of thumb for Microsoft issued service packs is that you should have approximately 4 times the size of the service pack itself as free space.

So for VS2008 SP1 update, you need 4 x 800MB == 3.2GB of free space on C:\
It might be possible to manipulate it a bit by setting %temp% to another drive or so. Whatever.

How not to ask question on a forum

vanDooren — Mon, 06 Oct 2008 06:29:00 GMT

Here is another person who needs to learn some netiquette (emphasis mine).

Hey,
well, I will not describe my situation because it is not part of my question and has nothing directly to do with it and would only lead to false assumptions as it already did...
My question is ... <snip>
Not that I am implying anything, but seeing that the discussion may drift to an entirely different topic directly, please do not return the question of why I am wanting to do this. I do know what I am doing and why I would need this.

Any help would be greatly appreciated.
Regards,
pd

His question would have a much better chance of being answered if he'd recognised that the people answering questions are actual people. We are volunteers, doing this to help and because some questions are actually very interesting. Treating us like helpdesk personnel is not something that we generally appreciate.

We sometimes spend a lot of effort to answer a complex question if the situation is very interesting. Or perhaps because the issue is something advanced that might be helpful to ourselves one day. Denying us the interesting bits and treating us like a bad manager treats his serfs is more likely to cause the reaction 'well, in that case figure it out on your own'.

And apart from the fact that the motivation to answer has left me already, the thing with complex questions is that the devil is in the details. If you don't tell us exactly what you are trying to do, and which problem you are trying to solve, then how are we supposed to know a) what causes the problem, and b) how to solve it.

EDIT: I discovered after some digging that he had asked this question before, and the original thread was closed by a moderator because it could be useful to malware authors. Personally I don't agree with this decision. But the OP should have mentioned this in his new thread. That way we would have known something more. And it doesn't change the fact that he should have described his problem more clearly.

Programmer discovers that floating point numbers have a floating point

vanDooren — Thu, 02 Oct 2008 05:05:00 GMT

I hang out in the MSDN forums on a regular basis, to see if there’re any questions that need answering. Usualy this is pretty unexciting, but every now and again, the asker really needs a reality check.

This thread came up some time ago, and it refuses to die.

The first thing that stands out is the title itself : ‘A very serious bug in MS Visual C++’. Sensationalist headlines like this almost always indicate a serious misunderstanding on the part of the author. It also indicates someone who is very, very sure of himself, because it excludes any possibility that he himself might be wrong.

The initial message itself was the classical example of ‘newbie discovers floating point numbers, it’s the end of the world as we know it’

If you haven’t bothered following the link, this is his gripe:

            double a=111.567,b=111,c;
            c=a-b;

            // and you will receive
            //
            //a=111.56699999999999
            //b=111.00000000000000
            //c=0.56699999999999307
            //
            //instead => a=111.567, b=111, c=0.567;

Yawn… another programmer who discovers that the floating point format does not guarantee fixed decimal correctness. The results are correct within the required precision of the floating point format, so all is well.

A is no 111.567 because it is a floating point number, and not a fixed point number. In any case, googling for ‘what every computer programmer should know about floating point’ will get you a paper that explains this issue in detail.

The original poster also explains that he has tested with every compiler from VC6 to VC2008, and they are all wrong. That in itself should have been a clue to think twice before using such a preposterous title.

Various people tried to explain the problem, but to no avail. Here are a handful of quotes from the OP (who is building an ERP system...) in the course of the discussion:

· Industry standard ??? I am not agreeing with you. There are laws of mathematics which must be respected by all. I can not agree that 111,567 is equal to 111.56699999999999 because of simple reason that it is not equal.

You cover me with theory. Thank you. But things are much simpler.
I think that something fundamental such as a declaration of fractional numbers and their actions should not be in so surrounded way. I think that the variables with floating point ('double') are unusable at this time, because they do not always give accurate results. And I would like experts from Microsoft, which deal with these issues, in some way to offer basic solution to this problem.
All indicate the standard IEEE as a dogma. I am not familiar with the IEEE simply because I do not have time. But once the standard makes it impossible to use a certain type of fundamental variables and actions with them, maybe it is better to consider changes in the standard

But it gets even better! A second poster enters the discussion with the claim

‘I am absolutely astounded by two things here:
1. That this math bug is still floating around (I remember when it was a CPU issue)
2. That people here claim that it is not a bug in c++ in VS2003 or later’

Someone then explains that his SUN stations give the same results, just to indicate that this problem has nothing to do with compiler errors (or CPU dependency) whatsoever.

But it wasn’t meant to be. What did the second poster reply?

‘Thanks for testing it for me on the SPARC system.
Perhaps it is some bizarre feature of hardware-based floating point present in modern CPUs? This may account for why similar code compiled on older compilers (VS6) (who don't have modern FCPU knowledge) yields expected results.

…

It's a bit amusing when the system can't even handle a result with one decimal place!’

Ah well.

If people are misguided, you can do your best to make them see. But if they want nothing to do with ‘reality’, then you can’t force them to understand.

After all, the powers of reason are futile in face of the powers of persuasion that allow someone to think every CPU, compiler and engineer / programmer / scientist in existence is wrong.

Windows 7 Engineering blog

vanDooren — Wed, 01 Oct 2008 13:47:00 GMT

I just stumbled upon the engineering blog for Windows 7. Seems interesting enough to follow in order to have a better idea about what Windows 7 will be like from a technical point of view.