Wikipedia:Reference desk/Archives/Computing/2008 September 19

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September 19

YouTube

1. On my computer, Youtube videos load very slowly. It can sometimes take an hour for a whole video to be playable. How can I fix this?

2. What is the highest number of videos that one Youtube user has and who is that user?

February 15, 2009 (talk) 03:00, 19 September 2008 (UTC)

As for 1, what sort of internet connection do you have? Who's your ISP? If you simply have a slow connection, there's no way to speed it up. As for 2, I have no idea how you'd find that out, sorry. --Alinnisawest,^{Dalek Empress} (extermination requests here) 04:04, 19 September 2008 (UTC)

1) If you're using wifi you may simply be near the outer range of your Wifi hub's signal. (Indoors, This will be a lot less than the advertised range, usually.) APL (talk) 17:26, 19 September 2008 (UTC)

MS Access Database Issue

I have a database table with a field with around 800 records. The vast majority are null/empty (aroun 600) and the rest have a value. For some reason when filtering by 'null' only 47 of the records retrun when it should be 600. I have checked and these fields are definitely empty (i.e. no value, no spaces, no nothing). I've even done update-queries that add a value to each of the blank cells. Then I filter by that value and they all appear. I then find/replace said value with nothing and...back to the same issue. Any ideas what could be causing this? 194.221.133.226 (talk) 11:31, 19 September 2008 (UTC)

Null and an empty string ("") aren't the same thing. Instead of doing SELECT * FROM myTable WHERE myField=NULL try SELECT * FROM myTable WHERE myField=NULL OR myField="". If that doesn't work, try SELECT * FROM myTable WHERE Nz(myField,"")="" (which is similar but a bit slower since it uses an extra function). --98.217.8.46 (talk) 13:38, 19 September 2008 (UTC)

Overhead cost of get and set methods

In C++, C# and Java, if a class variable has the simplest possible get and set methods, how much slower will they run than if the underlying variable were public and other classes accessed it directly? Will compiler optimizations make any difference to this? NeonMerlin 14:16, 19 September 2008 (UTC)

Without optimization, overhead can be considerable compared to just setting the variable, basically:

• return address stacked
• address of the method to call fetched (direct call possible in C++ if not virtual)
• address of the object and parameter stacked
• method called
• address of the object and parameter popped out of the stack
• object's variable set with parameter
• return to caller from address on the stack

Now that's naïve compilation, any decent compiler will just have the variable set and be done with it. Anyhow, don't hand-optimize before you know you have a bottleneck, and preferably use optimization hints (such as "inline" in C++) if it comes to that. Equendil Talk 15:00, 19 September 2008 (UTC)

In any situation where the get/set methods could be replaced with direct field access, the cost will typically be the same either way. The get/set methods might be more expensive if optimizations are turned off or (in C++ only) if the method body isn't visible to the compiler. -- BenRG (talk) 17:18, 19 September 2008 (UTC)

Also of note... If you are not validating data in the set, you will end up validating it elsewhere. The point of a set is to ensure that object data is always valid and doesn't need to be validated elsewhere - which would be extra overhead. -- kainaw™ 02:14, 20 September 2008 (UTC)

C++ compiler

Hey , I want to learn C++.But to practise it ,what compiler or language interpreter is to be needed for my windows.what about Turbo C++ Explorer?Any suggestions please.Cheers —Preceding unsigned comment added by 137.101.129.155 (talk) 16:18, 19 September 2008 (UTC)

You can download a free version of C++ from Microsoft. Their C++ implementation used to be abyssmal but they've got their act together now. Just ignore all their .Net and MS Windows stuff and you'll get very good standards compliance. Dmcq (talk) 19:51, 19 September 2008 (UTC)

That would be MS Visual C++ 2008 Express Edition. -- Finlay McWalter | Talk 21:51, 19 September 2008 (UTC)

Actually, that's the free IDE. The free compiler, Headers and tools are officially released separately as part of the Windows SDK. As for the actual compiler implementation, i've always known Visual C++ to be exactly to the Visual C++ Specification and when they claimed conformance with other Specs later on, they were matching then as well. - Jimmi Hugh (talk) 17:44, 20 September 2008 (UTC)

There is also the Dev-C++ environment, which comes with MinGW variant of the highly regarded gcc. -- Finlay McWalter | Talk 22:00, 19 September 2008 (UTC)

Eclipse Ganymede edition? I use it for programming C in embedded device is quite amazed at how it is comparable to commercial IDE's in terms of ease of use and exceed them in terms of functionality. --antilived^{T | C | G} 06:23, 20 September 2008 (UTC)

Silent Laptop

I am in the process of buying a new laptop and one of the most important features on it is that is must be silent. Besides reading the reviews and choosing a good one, what else can I do? I thought about buying a solid-state drive. Is there anything else that I can do? Perhaps exchanging the fan?Mr.K. (talk) 16:21, 19 September 2008 (UTC)

To what degree is performance important? What about keyboard size? If neither matters, subnotebooks like the ASUS Eee PC tend to have no moving parts, and are totally silent. The downside is that subnotebooks are too slow to play modern games, may be too slow for things like YouTube or watching DVDs, and have cramped keyboards.

If you need a more powerful laptop, the general tradeoff is that more power requires more cooling, which means a noisier fan. Laptop hard drives are nearly silent these days. --Carnildo (talk) 19:49, 19 September 2008 (UTC)

Carnildo is right, the hard drive question doesn't really come into it. Solid state drives, are far too expensive per gigabyte to equal hard drives to the same size. Save yourself some money and stick with convention. As for fans, oil cooling is a promising concept. It is silent, and hugely effective. No-one has ever tried it on a laptop.My name is anetta (talk) 22:13, 19 September 2008 (UTC)

Well weight might be a factor, oil is not that light and will add weight to the laptop for sure. Another factor might be that laptops have plastic covers, unlike PC with metal case, so that hinders the overall heat dissipation of the oil itself, and an aluminium-alloy case will increase cost by quite a bit. --antilived^{T | C | G} 06:21, 20 September 2008 (UTC)

If you have some more money left, you could get an Apple MacBook or MacBook Air, these thingies are really silent (but can heat up your balls if you have it too long on your legs!) HardDisk (talk) 08:01, 20 September 2008 (UTC)

Well, thanks for the infos so far. I thought about an SSD not because normal HD makes too much noise, but because they heat the laptop. I thought an SSD would not produce so much heat. —Preceding unsigned comment added by Mr.K. (talk • contribs) 08:24, 20 September 2008 (UTC)

That's news for me! Since when did the hard disk overcome the processor to become the hottest object in your laptop? Kushal (talk) 13:08, 20 September 2008 (UTC)

HD heat is insignificant. If you want a (physically) cool laptop (as well as silent), you make things a lot more difficult. You see, the slower a fan goes, the quieter it gets. But also hotter.My name is anetta (talk) 14:35, 20 September 2008 (UTC)

sun solaris os

How can I use intialisation file to customise my desk top environment?41.219.201.193 (talk) 17:51, 19 September 2008 (UTC)

Video Streaming Rates

I was reading through Data rate units#Megabit per second, and the numbers don't add up. For example, assume that there is a DVD (4.7 GB), which is 4,812,800,000,000 bits. The DVD is 2 hours, or 7200 seconds. Divide 4.8 trillion bits by 7,200 seconds and you get 668,444,444 bits per second, or 668 megabits per second. The 8 Mbits per second number given only results in about 950 MB for a two-hour movie.--Keepsbooks 44 (talk) 18:57, 19 September 2008 (UTC)

You have a few mistakes in your calculations. First of all, it's not 4,812,800,000,000 because while you're on the right track about multiplying by 1024, it's actually (~4.7) * (1024)^3, or ~5,046,586,572.8 bytes. Divide this by the 7,200 seconds and you get 700,914.8 bytes per second. Divide this by (1024)^2 and multiply by 8 (to get bytes->bits), and you get 5.348 Mbit/sec. At 8Mbit/sec, a 2hr movie would be 7.03125 GB, not 950 MB. -Wirbelwindヴィルヴェルヴィント (talk) 19:17, 19 September 2008 (UTC)

Google Calculator is handy for this kind of calculation. Single-sided double-layer DVDs hold up to 8.5GB, so 7GB for the movie makes sense. — Matt Eason ^{(Talk • Contribs)} 19:22, 19 September 2008 (UTC)

OK. Thanks. I forgot about the 8 bits per byte thing.--Keepsbooks 44 (talk) 19:39, 19 September 2008 (UTC)

Careful: single-layer DVDs hold about 4.71 × 10⁹ ≈ 4.38 × 2³⁰ bytes. Double-layer DVDs hold about 8.54 × 10⁹ ≈ 7.96 × 2³⁰ bytes. -- BenRG (talk) 22:43, 19 September 2008 (UTC)