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July 11

Algorithm for Union of Sets

Let us denote ${\displaystyle I=\{1,\dots ,n\}}$, and denote ${\displaystyle P_{k}(A)=\{B|B\subseteq A,|B|\leq k\}}$.

I am looking for an efficient algorithm to transform ${\displaystyle \{A_{i}\}\in P_{n}(P_{n}(I))}$ into ${\displaystyle \{\cup _{a\in A_{i}}{a}\}}$.

Thanks in advance! 31.154.81.65 (talk) 10:25, 11 July 2016 (UTC)

Expressed with words, ${\displaystyle P_{k}(A)}$ is a set of k-element subsets of some ${\displaystyle A}$, right?

Then ${\displaystyle P_{n}(I)}$ is a set of n-element subsets of ${\displaystyle I}$. However, ${\displaystyle I=\{1,\dots ,n\}}$ is itself an n-element set, so it has just one n-element subset: ${\displaystyle I\subseteq I}$, hence ${\displaystyle P_{n}(I)=\{I\}}$.

Consequently ${\displaystyle P_{n}(P_{n}(I))}$ is a set of n-element subsets of a singleton ${\displaystyle P_{n}(I)=\{I\}}$, so it is ${\displaystyle \{\{I\}\}}$ if ${\displaystyle n=1}$, or an empty set otherwise.

Alas I can't get the ${\displaystyle \{A_{i}\}\in \ldots }$ part. Do you mean 'a singleton belonging to'...? If so, ${\displaystyle \{A_{i}\}\in P_{n}(P_{n}(I))}$ could only be ${\displaystyle \{A_{i}\}=\{I\}=\{\{1\}\}}$, so ${\displaystyle A_{i}=\{1\}}$ for ${\displaystyle n=1}$ (and does not exist at all for ${\displaystyle n\neq 1}$) and I can't see the reason for the ${\displaystyle i}$ index at ${\displaystyle A_{i}}$... --CiaPan (talk) 12:07, 11 July 2016 (UTC)

I'm sorry for the typo... I fixed my mistake (replacing equality sign with inequality sign). 31.154.81.65 (talk) —Preceding undated comment added 13:36, 11 July 2016 (UTC)

So, P_n(I) is simply the power set of I (where I = {1, 2, ... n}), and could be denoted P(I). Then P_n(P_n(I)), or more simply P_n(P(I)), is a truncated power set of P(I), containing only those sets of sets which have n or fewer elements from P(I). And your {A_i} is an element of that truncated power set of the power set?

In other words, you have a list of at most n lists of integers, the integers themselves ranging from 1 to n, the lists of integers presumably unsorted, with the additional constraints that the individual lists of integers have no duplication and that no two lists of integers from your list of lists would be the same even if sorted, and you want an efficient way to merge this list of lists into a single list containing, without duplication, exactly those integers which appeared in any list of your list of lists. Presumably you hope that these constraints will allow for a more efficient algorithm. Note that our article merge algorithm discusses the merging of sorted lists; I don't know what we have on the merging of unsorted lists without duplication. -- ToE 14:51, 11 July 2016 (UTC)

Okay, I'll read the article about merge algorithm carefully. Thank you for the idea to read this! 31.154.81.65 (talk) 05:55, 12 July 2016 (UTC)

If you can tell us your actual task, it would help us know if we are up against an XY problem. The multiple roles of n -- it is both the maximum value of the integers in your sets and is the maximum size of the elements which are in the truncated power set of the power set of I -- strike me as unlikely to arise naturally.

Your task, as I understand it, has the (perhaps slight) advantages over simply merging unsorted lists with possible duplication in that you know that the individual sets of integers themselves contain no duplication. Note that some languages offer set abstract data types which are often implemented "using more efficient data structures, particularly various flavors of trees, tries, or hash tables." Our article mentions the expected union and add operations, but I see that Python's built-in set type also offers an update operation, which "update the set, adding elements from all others." (In essence, a ∪= augmented assignment.) Even if you wish to roll your own solution, the library implementations may offer suggestions for optimization. -- ToE 20:31, 12 July 2016 (UTC)

• Assuming ToE did represent correctly the problem, a solution that is optimal in time (but disastrous in space) would be to read all the lists once to find the maximum value ${\displaystyle n_{max}\leq n}$, then create a boolean array of ${\displaystyle n_{max}}$ elements set to false, then read all the list and flip the bits in the array when the value is found. If you know ${\displaystyle n}$ you do not even need to do the first pass, and there is no way to do it more efficiently (you will eventually have to read all the elements of all the lists, and practically, the bit-flipping is easy to vectorize in many programming languages such as Python). Returning the sorted union is trivial then.

The downside of course is that if there is reason to suspect that ${\displaystyle n_{max}}$ is much larger than the size of the final list, the array will be much bigger than it would need to be by other methods. Tigraan 09:01, 12 July 2016 (UTC)

uninstall Yahoo! powered

Yesterday I installed an update of Freemake Video Downloader. It seemed to install a browser hijacker. It installed "Yahoo! Powered" and I can't uninstall it. Is that a browser hijacker? Bubba73 16:44, 11 July 2016 (UTC)

Well, I ran Revo Uninstaller and that seemed to get it. Bubba73 19:22, 11 July 2016 (UTC)

That would be Search.yahoo.com browser hijacker -- There are instructions for manual removal which are somewhat complicated (depending on OS & browser). This seems to be the most recent and comprehensive:. --2606:A000:4C0C:E200:A073:98E5:BA6B:E905 (talk) 23:35, 12 July 2016 (UTC)

July 12

Would the graphics card R9 390X or gtx1070 fit on the motherboard GA-H81M-S1?

Would the graphics card R9 390X or gtx1070 fit on the motherboard GA-H81M-S1?201.79.70.197 (talk) 12:19, 12 July 2016 (UTC)

It should since those you mentioned are standard PCIe video cards anyway, but what matters more is if they fit inside the case you're using. Blake Gripling (talk) 12:57, 12 July 2016 (UTC)

And you want to make sure it works with the power supply. The GTX1070 is rated around 150W, so it should work easily with any power supply that is at least 500W. The R9 390X is rated around 250W. So, you will want 600+W. Because the price isn't much different between 500 and 600W power supplies, I usually get more than I need. If you are using a small power supply (like a 350W that comes free with many cases), you will have issues with using either card. 209.149.113.4 (talk) 14:10, 12 July 2016 (UTC)

Oh Yes, I know about the power supply thing, and I will buy one if needed. Anyway my current Graphics card is gt 730. Thanks for the help 201.79.78.164 (talk) 16:53, 12 July 2016 (UTC)

While the case is far more likely to be a problem, I wouldn't assume they definitely fit all motherboards. Some motherboards may place components (particularly heatsinks) which will block excessively long cards, either for the main slot or the second slot if it's a double width card (as many are). Admittedly this isn't very common nowadays for a single card, still you should always check. I don't know what the PCIe standards for physical clearance are but I'm pretty sure they did not and possibly still don't require the sort of physical clearance some cards need. So a motherboard could be fully compliant but still not be able to fit the card. Nil Einne (talk) 06:02, 13 July 2016 (UTC)

Movie maker sought

What is highly praised?

Requirement is, something that can make me select points (from and to) of a video clip, more than one time in one go… – An easy to use tool is sought. A portable software is desirable, however…

Apostle (talk) 18:11, 12 July 2016 (UTC)

Arranging video clips in a desired sequence can be done using a program called a Non-linear editing system. Misplaced Pages has a List of video editing software and a Comparison of video editing software. AllBestFaith (talk) 23:41, 12 July 2016 (UTC)

Password Protector; Lockdown protection sought

Peeps, what’s highly praised? Btw, I possess Folderlock (currently installed; this provided Bitlocker – I believe bitlocker is unbreakable, and good, unless you guys re-correct me), Keepass (Portable acquired, and wired), AxCrypt (needs internet connection)... -- Apostle (talk) 18:17, 12 July 2016 (UTC)

Apostle, it is not clear what your question is. Are you asking for "consumer feedback" about some encryption products? If so, Misplaced Pages's reference desk is probably not the place to use; it is intended for factual questions (eg "which company sells product X") rather than opinion. Tigraan 11:33, 13 July 2016 (UTC)

If you read Misplaced Pages's article on BitLocker you will see that it is good but not unbreakable.--Shantavira| 14:38, 13 July 2016 (UTC)

July 13

Windows 9x

Theoretically if Microsoft had continued to develop and invest in the DOS-based Win9x line instead of switching to NT, could they have produced a 64-bit OS running on-top of DOS that took full advantage of modern hardware capabilities? — Preceding unsigned comment added by 89.185.7.252 (talk) 14:39, 13 July 2016 (UTC)

There is no reason that DOS couldn't be altered and compiled to take advantage of a 64-bit CPU. Keep in mind that jumping to 64-bits isn't always an advantage in every single possible application. So, playing an old DOS game in 64-bit DOS won't make it better. 209.149.113.4 (talk) 16:06, 13 July 2016 (UTC)

Well, this entails a sort of Sorites paradox.... When does a sufficiently-modified DOS system cease to be DOS anymore? If you add all the code, piece by piece, to make DOS behave like a modern system... haven't you ended up replacing it with the modern software?

A lot of features you take for granted today were absolutely missing from DOS. For example, the DOS operating system provided very little in the way of memory management, and essentially zero memory protection. Could you use a modern Intel CPU architecture in real mode and still call it "64 bit"?

DOS did not provide multiprocessing. There was no thread model, and there was no process model; these software abstractions simply did not exist and were not provided as a system service; obviously, there was no multi-CPU support either. Application software either ran serially, or used hardware interrupts, or used an application-provided threading model.

DOS never provided support for the internet protocol. The entirety of computer network application software that we now know and love - things like web browsers, for example - would require application-provided network abstractions and hardware device drivers.

You can read about DOS in our articles; and if you are technically adept, you can study FreeDOS and DOSBox, or download their source code, to see what DOS programming looks like in the 21st century.

Don't be fooled by superficial appearances: although many new systems provide a command line interface, modern systems are very dissimilar from DOS. DOS did very little, compared to modern system software; consequently, many DOS application programmers had to write lots of difficult, non-portable software to make their application features work. You should not fall into the trap of conflating all text-mode systems with DOS. For example, you can run a terminal or shell in most operating systems, but that's not DOS. If you really dislike colorful graphics, you can boot modern Microsoft software - or linux or OS X, for that matter - to a text-only-mode command-line terminal... but these modern operating systems still do things much differently than DOS.

Nimur (talk) 09:04, 14 July 2016 (UTC)

I'm not sure I understand the point you are trying to make. You go on and on about the limitations of DOS, such as lack of network support, memory management, web browsers, protected mode, etc but ignore the fact that versions of Windows built upon DOS such as Windows 95, 98, and ME provided all of those things. Since the question was about a hypothetical modern version of Windows built on DOS, I do not see how limitations of vanilla DOS that were overcome years ago in previous versions of DOS-based Windows are at all relevant to this question. 89.185.7.252 (talk) 12:36, 14 July 2016 (UTC)

Maybe it will help if you clarify exactly what you think DOS is. Have you read our article section on its system design? Nimur (talk) 18:09, 14 July 2016 (UTC)

I'm not sure why you are still going on about DOS. I asked about Windows9x which uses DOS as a boot loader but is obviously not DOS itself. I don't need to explain to you what DOS is since I didn't ask about DOS, I asked about Windows9x. Maybe reading the article will help you? You're acting as though I asked if DOS itself could be turned into a 64-bit OS with a GUI (which obviously it could) and then debating with yourself about whether such a system should still be defined as "DOS", but that wasn't what I asked at all. It's quite clear that my question is about Windows9x, not DOS. The title of this section is even "Windows9x". So quite why you are so determined to derail my question into a debate on DOS is a mystery to me. 92.46.125.19 (talk) 18:29, 14 July 2016 (UTC)

Instead of the paradox you mentioned, how about the ship of Theseus paradox, which deals with replacement of components rather than removal ? StuRat (talk) 12:03, 14 July 2016 (UTC)

For the sake of comparison, Linux (and yes, I am specifically talking about the Linux kernel here) originally ran only on Intel 386 systems. Finnish keyboard settings were actually hardcoded into the initial release! The Linux kernel of today has basically no code from the original 1991 kernel. So the answer is yes, Microsoft could have decided to retrofit DOS bit by bit into a modern operating system. They decided not to because they felt the Windows NT architecture was more elegant and extensible (Dave Cutler, who previously worked on the venerable VMS, was lead designer), and switching to it would eliminate the technical debt of the Windows 9x line, as well as the redundancy of maintaining two separate operating system product lines. --71.110.8.102 (talk) 03:07, 15 July 2016 (UTC)

What happens exactly when you clone your SIM card

If you clone your SIM card and use both the new and old card at the same time, how will the phone company react? How will they discover it? Is there a central server with a list of all numbers and where they are? What if one card accesses the network through roaming? Llaanngg (talk) 16:21, 13 July 2016 (UTC)

Yes, they do keep a database, See Network switching subsystem#Home location register (HLR), International mobile subscriber identity, and Mobility management. There are special clone SIMs that disables the first SIM when switched on, but as far as I know the carrier has to turn on support for such devices.

Also see:

• https://security.stackexchange.com/questions/64294/how-does-a-sim-card-prevent-cloning
• Radio fingerprinting (warning: poor quality article; needs to be expanded and references added)

--Guy Macon (talk) 18:13, 13 July 2016 (UTC)

Spy potential of Pokemon Go

I've been seeing a wave of newsvertisements for Pokemon Go that is unrivalled since, well, Facebook Live's snuff video PR campaign, including inducing players to jump a fence to find a dead body, and it's left me thinking about how useful this app may or may not be to spy agencies, police, or even ordinary private dicks.

• Who is in charge of placing the Pokemon monsters or other targets? Is there a straightforward way for a third party to set up an attractive feature on some property they want inspected?

• How do players find the targets they are looking for? Is there a general 'directory' that leads them to the land they are supposed to reconnoiter?

• Is the game known to upload the video the phone is taking in order to put the cartoon figure on the screen, or is that done locally?

• Does the game have a way of collecting data about things in the area, e.g. other cell-phones, Wi-Fi identifying numbers, etc.?

• If a player trespasses in order to happen across evidence, is there any possible legal argument that he is a "police agent" if it could be shown that police put the target on his map, or does his personal decision to trespass to play the game put an end to any attempt to claim a warrantless search?

• I've read about players being lured to police stations to hunt Pokemon, with cops complaining about it; is there any way to lure a particular player to a police station without luring all of them, say if that particular one had outstanding warrants?

• Are players being lured near crack houses and other highly hazardous features that someone might want to have periodic video surveillance of? I didn't see this one but it seems like an understandable "accident" to have happen.

Wnt (talk) 23:00, 13 July 2016 (UTC)

Update: there's a discussion of this here and better here; some users are skeptical that there is video uploading going on based on the reported bandwidth. However, apparently the app actually has the user take a picture, which is a more limited amount of data. The privacy policy is here and doesn't specifically say video is uploaded; it's wording is pretty much the longwinded way of saying "absolutely none" used in any privacy policy online. One user said that "Pokemon GO is owned by Niantic, Inc, which was formed by Keyhole, Inc, which was funded by the CIA's venture capital arm In-Q-Tel". Checking this out, the second part is true (see Keyhole, Inc); the first part omits that Keyhole was first acquired by Google, putting its cofounder in charge of Google Maps (gee, never would have guessed...) before eventually the department was spun off as Niantic. I don't know how much this really means though, since I don't actually know nowadays that it is possible in a capitalist economy for a company to be created without the CIA effectively in charge of it. Also, none of this really answers the practical questions, just reinforces the underlying suspicion. Wnt (talk) 11:47, 14 July 2016 (UTC)

• OK... So, you are at the reference desk, made to ask factual questions, not to promote tinfoilhattery. While "is there a large-scale conspiracy that released Pokemon Go to improve their spying" is somewhat factual, it is unreasonable to expect Misplaced Pages editors to give an appropriate answer (although Occam's razor likely applies).

Did the CIA/Mossad/whatever fund the development/release of PG to improve their sensors? Probably not. Does the CIA/Mossad/whatever try to interfere with the players' connections to snoop on their private data? Probably.

Does the CIA/Mossad/whatever pay/coerce the Pokemon Go Head of Spawning Operations (or hacked the servers that handle that task) in order to push some people to some places for some reasons? Unlikely. It is not cost-efficient for the rabble, and getting a tracker (GPS data exchanged between the PG servers and the player's device can be more easily intercepted than spoofed) on a mafia boss or international terrorist is so valuable that you do not want to lose it if they feel there is something weird with the spawns.

Tigraan 15:48, 15 July 2016 (UTC)

Link Sought

Pokemon Go for PC and .apk for Smartphone is sought please. Regards. -- Apostle (talk) 04:31, 14 July 2016 (UTC)

Pokemon Go for PC doesn't exist, but this article tells you how it can be done using an Android emulator. It was the first result when I googled "Pokemon Go for PC". I don't use them myself, but I assume the .apk file can be obtained from the usual app sources. Rojomoke (talk) 14:13, 14 July 2016 (UTC)

• Downloading .apk from third party sources is probably a bad idea, since (1) such third-party may have added any code they like (that you will not like) to it, (2) the standard process of updates is broken, and other potential issues. PG is available for download through the usual sources if you are in the area of deployment. Tigraan 15:48, 15 July 2016 (UTC)

• It's possible to play Pokemon Go on the PC using an emulator and GPS spoofing, but that's against the terms of service of the game and will likely get your account banned. As for a download for smartphones, Ars Technica has a decent guide. As Tigraan said, third-party sites may maliciously modify the APK, so download at your own risk. clpo13_(talk) 16:02, 15 July 2016 (UTC)

The big problem with third-party sites is the attitude that they MIGHT add malicious content to the code. There is a very minuscule chance that there might be some malicious content. Out of a billion files, you might find one that has malicious code. That is completely false. The reality is that third-party sources usually host malicious code. The often host malicious code. You should expect malicious code. Even well-known sources like CNet have been known to add malware to the code (mainly adware/tracking code in CNet's case). So, this comment will be followed up with complaints that unless someone specifically exposes malware for a specific file, we should all assume that malware doesn't exist and download all the crap we find on the Internet. Please think it through. Why would someone pay money to host "Free" files and pay money for bandwidth so you can download them? It isn't because they are nice people. 209.149.113.4 (talk) 17:50, 15 July 2016 (UTC)

Noted, and thanks all. -- Apostle (talk) 18:51, 15 July 2016 (UTC)

July 14

Printer

A Reliable and durable printer sought that can imprint a lot of papers with as less ink as possible. – say 3,000-5,000 pages in one go, 500 times with one inkjet or so. Also:

1) What kind of printers use heat/laser as ink, imprints on a special/non-special kind of paper? And, how much is it (both)?

103.230.105.13 (talk) 22:46, 14 July 2016 (UTC)

HA Ha Ha Ha!!!--86.187.174.181 (talk) 23:30, 14 July 2016 (UTC)

To clarify 86's comment, the OP's specifications are appropriate for a serious commercial printing establishment, not for a SOHO environment. This is Canon's range of printers for those sort of volumes - other suppliers are available. But we are talking printers that cost about as much as a typical car. Tevildo (talk) 00:13, 15 July 2016 (UTC)

See what toner is. The plastic dust gets molten onto paper. Todays multi function office machines, not at the SOHO entry level might already fulfill this need as dedicated printer or copier. One manufacturer owns a patend for automatic switching feed paper from next drawers. Large volume drawers with electric lift for feeding paper from top can load usually 2,000 to 3,000 sheet at once. This expensive machines make 25 to 80 prints per minute. But thats not the price and performance limit. --Hans Haase (有问题吗) 06:22, 15 July 2016 (UTC)

Password-protecting SD cards

I bought an SD card for the sole purpose of tearing it down. But, instead of doing that, I want to know if I can play around with the password protection, temporary write protection, and permanent write protection mechanisms of it using a standard computer SD card port. I've read that most reader hardware does not have the capability to use these commands. Is this true? — Melab±1 ☎ 23:40, 14 July 2016 (UTC)

Have you checked whether the Secure Digital article, or the resources it links to, answer your questions? --71.110.8.102 (talk) 02:35, 15 July 2016 (UTC)

July 15

File-system, external storage, unsafe removal

Do different file-systems behave differently, when an external storage medium is removed unsafely? That is, it's connected through USB and I just pull it. Would something like ext3 be more reliable than NTFS? Hofhof (talk) 00:43, 15 July 2016 (UTC)

It depends on what features the filesystem has. ext3 and NTFS have rough feature parity—both are journaling file systems—so between those two there's unlikely to be any significant difference. Other features like copy on write (not present in those two file systems) can also prevent filesystem corruption in some situations. It should go without saying that you should not make a habit of unsafely removing storage devices, and no file system features are a substitute for backups. --71.110.8.102 (talk) 02:32, 15 July 2016 (UTC)

Aging of flash memory is caused by writing. So flash memory devices are written as less as possible. Removing the unsafe way may cause a lost of recent updates of the journal. Depending on the file system, when the journal is redundant, it is more robust due copies can be compared to the file it points and the checksum. --Hans Haase (有问题吗) 06:11, 15 July 2016 (UTC)

Here is an interesting (if somewhat old) overview of the journaling behavior of various file systems. ext3 has three journaling modes, and I gather that NTFS's journaling is more or less the same as ext3's middle level ("ordered"). What this means is that you won't end up with a broken filesystem that needs fsck/chkdsk, and you won't end up with random crud (or zeroes) in a file that was never written to it, but you may end up with out-of-order overwrites. That is, if you overwrote data chunks A, B, and C in that order, then yanked the drive too early, you might find that A and C (or even parts of them) made it to the disk and B didn't.

Note that these guarantees apply to disks that support some measure of data integrity in the first place. I've heard horror stories of SSDs being irreversibly damaged by sudden power loss (see ). That's reason enough to stop the drive first, regardless of the file system. I think HDDs are much better in this regard, even the cheaper consumer ones, but repeated sudden power loss may cause long-term damage to them too. -- BenRG (talk) 06:37, 15 July 2016 (UTC)

See SandForce and Write amplification to get an idea how this is working. A typical horror scenarior might be caused when the block is being relocated due its number of rewrites exceeded the maximum specified. If this relocating is a map as well, the question must be asked, where is its repair procedure tool? --Hans Haase (有问题吗) 06:54, 15 July 2016 (UTC)

Keybboard

My keyboard at some point completely ceased to function, and I am now using the super-tedious "on-screen keyboard". I likely bumped or hit something that caused this. My sleep-deprived brain is not working well, but I'm assuming this is a fairly simple issue. Any suggestions? Joefromrandb (talk) 02:04, 15 July 2016 (UTC)

Is that a laptop or desktop? Hofhof (talk) 02:20, 15 July 2016 (UTC)

What operating system are you using? Is this a wireless or wired keyboard? Have you checked that it's plugged in? If it's wireless, does it have working batteries? Have you tried restarting the system? --71.110.8.102 (talk) 02:34, 15 July 2016 (UTC)

It's a laptop. Yes, it's plugged in, and yes I've restarted it. I'm using Windows 10, if that's what you mean. Joefromrandb (talk) 02:45, 15 July 2016 (UTC)

Try to reinstall it using the add hardware wizard to install the driver package. Otherwise, you might need to replace the keyboards. In some laptops is rather easy to remove it. You could also try to remove it, reboot, and to connect it again.Hofhof (talk) 05:28, 15 July 2016 (UTC)

The most common cause of this I've seen is a stuck key/dirt in the keys. It fails a self test at startup and then it's disabled (using Windows, anyway). Just shut off the computer, run your hand back and forth over it a few times so all the keys clatter, and see if you have a keyboard. Wnt (talk) 10:17, 15 July 2016 (UTC)

If your laptop has a removable battery try this: Shut down the laptop, remove the power supply, remove the battery. Wait 1 minute, reinsert the battery, reinsert the power, and start the laptop again. Even when shutdown, laptops often keep the glidepad and keyboard powered up. Doing the above procedure will reset their microcontrollers. Otherwise, you can use an external USB keyboard for the laptop. LongHairedFop (talk) 11:36, 15 July 2016 (UTC)

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