## In what cases is solving Binary Linear Program easy (i.e. **P** complexity)? I’m looking at scheduling problems in particular

In what cases is solving Binary Linear Program easy (i.e. P complexity)?

The reason I’m asking is to understand if I can reformulate a scheduling problem I’m currently working on in such a way to guarantee finding the global optimum within reasonable time, so any advice in that direction is most welcome.

I was under the impression that when solving a scheduling problem, where a variable value of 1 represents that a particular (timeslot x person) pair is part of the schedule, if the result contains non-integers, that means that there exist multiple valid schedules, and the result is a linear combination of such schedules; to obtain a valid integer solution, one simply needs to re-run the algorithm from the current solution, with an additional constraint for one of the real-valued variables equal to either 0 or 1.

Am I mistaken in this understanding? Is there a particular subset of (scheduling) problems where this would be a valid strategy? Any papers / textbook chapter suggestions are most welcome also.

## Individuals Search by Cell Phone – Easy to Do Tips on How to Find People With Their C

In this universe of science and innovation, the men of science invest their energy in research facilities looking for something new. We additionally witness their push to manage natural products. Presently this time, it is an iPhone from the place of Apple that has been pulling in all the considerations worldwide in the course of recent months.
The device irregularities of US can purchase this iPhone right now. Yet, the individuals of Asian nations like India need to hold up to mid 2008 to lay their hands on such an enchantment development. The telephone has joined screen and consolidates the highlights of a cell phone, ipod, advanced coordinator and remote web gadgets. It is a progressive telephone. It does things that no telephone has ever done previously yet it has likewise been said that it needs includes found even on the most essential telephones. So it has welcomed both praise just as analysis.

iPhone is a small, thin, exquisite hand-held PC whose screen is a piece of touch touchy glass. The \$500 and \$600 models have 4 and 8 GB stockpiling and can store 825 and 1825 tunes individually. The iphone is assemblage of cellphone, video ipod, email terminal, internet browser, camera, morning timer, palm type coordinator and one hell of superficial point of interest. The telephone is so smooth and slender that makes Treos and Blackberrys look large. At the point when the glass of the telephone get smudgy, a sleeve cleans it off yet it doesn’t scratch without any problem. However, the greatest accomplishment in this telephone is the product accessible. It is quick, excellent, menu free and extremely easy to work. The main physical catch underneath the screen consistently opens the landing page showing the symbols for the iphone’s 16 capacities. Records look with a flick of finger; CD fronts flip over as it is flicked. The clients don’t need to check the phone message yet it itself checks the client. The just one catch press uncovers the holding up messages, recorded like email. There is no dialing in, no secret word. To answer a call, the client can tap answer on the screen, or squeeze the minuscule amplifier. iPhone has a speaker telephone and vibration mode however both are powerless. The music or video playback delays until you hang up. In any case, while making a call, be that as it may, the clients need to follow a protracted procedure containing 6 stages: wake the telephone, open its catches, gather the home screen, open the telephone program, see the ongoing calls or speed dial list and select a name. The call quality is simply normal yet email is fabulous. Approaching messages are completely designed, total with illustrations. The clients even can open Word, Excel and PDF reports however can’t alter. The internet browser is extremely commendable. It has different open pages, textual styles, designs, spring up menus, check boxes, interactive connections and dial-capable telephone number. Everything is finished with the tap of a finger.

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## Context

I found out my Linux server was infected.

Symptoms were : 100% CPU usage when idle, slow download speed, `iptables` rules keeps growing.

After finding the processes, killing it and all the possible ways it setup to restart again, I’m back with a normal-looking server (no symptoms).

I used this blogpost (in chinese) instructions to clean the system.

In the process of cleaning the system, I could save the script used by the hacker. It is available here : https://gist.github.com/Colanim/0c7d71b90893a54c731de4e328585e9f

## Question

I can’t fully understand this virus script, but it seems bad enough (scanning intranet ? Downloading weird files from weird domain ? Modifying `iptables` secretly ?). My question is : what should be my next steps ?

I have data on this server I need to keep.

Is the virus very bad and I should just wipe everything ? Is it ok to save the data and just do a clean Linux install ? Or if the virus is not that bad, can I keep my server in the current state ? (system seems clean, no symptoms anymore)

Should the passwords used in the server be considered leaked ? Or it’s fine because anyway it’s hashed ?

## Is there an easy way to remove the data-preserver-spaces span from blocks?

I converted a page from Classic to Guttenberg and now all the blocks have this span in them:

``<p><span data-preserver-spaces="true">...</span></p> ``

This means that all the blocks appear on a grey background, which makes it harder to edit, see links, etc.

I know how to edit the HTML and remove the `<span>` tag like so:

``<p>...</p> ``

but over 100 blocks, that’s definitely tedious. Is there a way to do that automatically? (like a "clear all formatting" like I’ve see in other editors?)

Here is an example of the effect I’m talking about:

Note that it also happens when text is Italic or Bold or some other such format (which I think is also annoying).

## From Analytics data, easy way to get % of visitors with a screen resolution of X or larger

Is there any easy way to use the Analytics data of a website, for example on google analytics, and query it to get the % of users with a browser resolution of X or larger?

It’s good to know the top used resolutions but for example I want to know if I can drop support for very small resolutions so it would be nice to know the % of users using 1024 or smaller for example.

I was wondering if there was an easy way to achieve this somewhere in G-Analytics or an external tool. Right now I’m parsing the raw data and doing this on a custom program I did.

## Multi check are too easy?

When asking for a skill check that all the players can attempt, it is quite easy to have at least one player to succeed.

Indeed, a 15 DC investigation (that is a 30% chance with a +0) is quite easy for a group of 5 PC (83% chance to succeed). Even a 20 DC would not be that difficult if there is enough people with a +3/+4.

How to manage group check to avoid the check to be too easy ?

To notice that I am not talking about a group check (in that case it looks that half+ of the player need to succeed), but rather a check that everyone can attempt one at a time (opening a safe, decipher a scroll, looking at an ancient item to know its history…)

## Is it reasonable to think that most magic users would be familiar with the spell Silence and thus know easy ways to counter it? [closed]

The spell Silence as described in the PHB:

For the Duration, no sound can be created within or pass through a 20-foot-radius Sphere centered on a point you choose within range. Any creature or object entirely inside the Sphere is immune to thunder damage, and creatures are Deafened while entirely inside it. Casting a Spell that includes a verbal component is impossible there.

The spell is obviously a useful tool against magic wielders, but I’m trying to get clarification on its limitations.

Would it be common for magic users to recognize the Silence spell and know easy ways to counter its effects? For example, a wizard familiar with the spell might know to just run a short distance in any direction to leave its area of effect, and then continue casting spells. I understand that different types of characters will have different knowledge of spells, but Silence isn’t a high level spell and would seemingly be well known to many mid- and even low-level magic users.

The related question below might shed light on how a character would react to the Silence spell, because they might instead interpret the effect as being deafened.

Related questions:

Deafness vs Silence – How to distinguish Darkness from being blinded and Silence from being deafened?

## Are the Power Word spells especially easy to identify?

There are various high level spells named “Power Word: X”. They are all verbal-only spells (except Power Word: Heal), and tend to have the following text in them(…except Power Word: Heal):

You speak a word of power that [has the effect of the spell’s name]

Assume for the purpose of the question that the rules from Xanathar’s Guide on spell identification are in use.

Do these properties (verbal only, verbal component is a single word rather than multiple) make these spells unusually easy to identify – not as a specific spell, but as “one of the Power Word spells”?

In other words, consider the following scenario:

Spellcaster A is facing off against spellcaster B. On B’s turn, B utters a single arcane word, and seems to not be using any somatic or material components for their spell.

Is it reasonable for A to deduce, without the use of a reaction, “ah, I reckon the single word and nothing else means it’s one of the Power Word spells. I had better Counterspell using a high level slot”?

## Is there a constant-space accumulator for a set of numbers to make it easy to test for set membership?

My question: What data structure or algorithm could I use to solve the following set membership problem efficiently?

Imagine I am generating a random 32-bit integer every second, and adding it to a list of N integers. Imagine that each time I generate an integer, I ship it (and any other information I might have easy access to) off to a client. Later, the client will submit an integer (along with any other information I have given it), and I want to be able to quickly determine if a given integer has ever appeared in my set, but I want to do it in constant time, using a small, constant amount of memory. In other words, I don’t want to just keep all of my generated numbers in a list or hash table and check the submitted integer against this list. Ideally, adding a number to this set is a constant-time operation. I do not ever need to delete numbers from the set.

Option 1: I could use a bloom filter and add each number to the bloom filter. Unfortunately, the set membership test would be probabilistic, but I could make the filter big enough to reduce my probability of a false positive quite low. I’m open to this approach, but want to know what other options I could have.

Option 2: I have been reading about cryptographic accumulators. If each of the numbers I was generating were prime, I believe I could use an RSA accumulator to store a single accumulator value of constant size. Each time I add a new prime to my set, I add it to the accumulator, then I generate its witness as well and ship both the number and the witness to my client. Later, the client would submit the integer it is testing and the witness, and I would be able to quickly determine if the number being submitted is in fact a member of my set or not. Possible problems: I need to be able to hash to a prime number deterministically. (Not the end of the world, but adds complexity) I think I have to update my witness values as I add new values to the accumulator. Lastly: My understanding of accumulators is rudimentary.

Possible modifications: 1: Would this be any easier if subsequent values in my chain of numbers were somehow dependent upon previous values in some way? You could imagine some sort of non-cryptographic hash chain, whose current hash value includes enough information about its previous values that it could quickly determine, “Yep, if my current hash value is X, and you submit Y, Y definitely was a previous member of my chain.” 2: If I understand them correctly, accumulators seem like a very space-efficient way to store sets of prime numbers (and perhaps other values), but in the literature they all assume potential adversaries. In my case, I don’t need my witness be be unforgeable, so I would think that would make the problem much easier to solve. Perhaps it just means that I get to use smaller constants (so I don’t have to use RSA-2048?). Or perhaps this simplifies my problem even further? 3: What if the “random” values I was generating were known to be increasing, or were simply timestamps? (I still need to know if that particular timestamp were ever used)

Related problems: This seems a lot like having a lot of hash values in a Merkle tree or hash chain (blockchain), and wanting to be able to determine if a particular hash value were ever seen in the chain, without having to store every value that had been seen in the chain. I’m hopeful that with the additional concept of generating a “witness” value of some sort to be stored along with the number, the server can make a membership determination with much less overhead than having to store all of the numbers. This also seems similar to a verifiable log or authenticated dictionary.