## Magento 2 – what does the require means in composer json?

"require": {
"segmentio/analytics-php": "^1.5",
}

This code is there in composer json, when i have composer update the segmentio lib version changed from 1.5 to 1.7 not sure why.

## Open WiFi Network Where All Confidential Communication is Encrypted Through Other Means

Imagine the following scenario:

• Users connect to an open WiFi network (no password, no encryption)
• All users stick to secure transmission protocols for all confidential data (HTTPS, SSH, VPN, etc.)
• Users devices do not accept any inbound connections

Would this scenario provide a reasonable level of security for the users involved? Or perhaps more importantly, does a malicious user’s presence on an unencrypted WiFi network pose a known threat to the other users?

## database design – What is the word that means a query predicate can use an index

I remember reading in a paper a word that means “query predicate can be evaluated using an index” but I can’t recall the word. For example if you had a table with a column called “name” and you had an index on name, then a query that had a WHERE clause involving “name” could be succinctly described by this word as “An X-able query”, where X is the word I don’t remember.

## linear algebra – Does Number of Pivots (Independent Vectors) Means Dimension of That Vector?

I’m confusing about one topic. Concider we have that matrix;

|1 1 2|

|2 1 3|

|3 1 4|

|4 1 5|

So we know that this vector has only 2 independent vector since col3=col1+col2 and it has 2 pivot. C(A) fills 2-D space inside 4-D space.

But how the vectors satisfying y=5 the equation form a 2-D space in 3-D?

Isn’t it this has only 1 pivot since (0 5 0) (x y z)? So why it’s not 1-D space in 3-D?

## dnd 5e – Can a Warforged’s Integrated Protection feature be bypassed by some magical means?

Integrated Protection states:

While you live, the armor incorporated into your body can’t be removed against your will.

This is not ambiguous. The armor cannot be removed against your will, unless you are dead.

D&D 5e has a specific beats general rule:

This compendium contains rules that govern how the game plays. That said, many racial traits, class features, spells, magic items, monster abilities, and other game elements break the general rules in some way, creating an exception to how the rest of the game works. Remember this: If a specific rule contradicts a general rule, the specific rule wins.

For a feature, such as a spell or monster effect, to be able to remove a warfored’s armor, it would have to explicitly create an exception to the Integrated Protection feature. No such features exist.

### The spell feign death might work, but it’s complicated.

There is a case to be made for the spell feign death creating a loop hole here. Feign death states:

You touch a willing creature and put it into a cataleptic state that is indistinguishable from death.

For the spell’s duration, or until you use an action to touch the target and dismiss the spell, the target appears dead to all outward inspection and to spells used to determine the target’s status.

One could argue that being in a state that is indistinguishable from death implies that I should not be able to determine you are alive by being unable to remove your armor.

But even if this is the case, the creature must willingly submit to the effect of feign death, so it probably couldn’t be used by a hostile creature to remove a warforged’s armor without significant deception.

This does raise the question, “can an unconscious creature be willing or unwilling?” Rather than rehash the discussion here, I’ll call “up to the DM” and direct you to these Q&As for further guidance:

So this comes down to choosing which feature to make weaker. Do you make Integrated Protection susceptible to feign death, or do you make feign death not as good for warforged? Discuss this with your DM if you anticipate these features ever interacting.

### Warforged aren’t magic anyway, so effects and spells that stop magic wouldn’t work anyway.

The Sage Advice Compendium contains detailed guidance for determining if a feature is magical:

Determining whether a game feature is magical is straightforward. Ask yourself these questions about the feature:

• Is it a magic item? [No]
• Is it a spell? Or does it let you create the effects of a spell that’s mentioned in its description? [No]
• Is it a spell attack? [No]
• Is it fueled by the use of spell slots? [No]
• Does its description say it’s magical? [No]

On the last point, nowhere in the race description of warforged found in Eberron: Rising from the Last War is it stated that warforged are inherently magical.

So a spell or effect such as the one created by antimagic field would not bypass Integrated Protection, because Integrated Protection isn’t magical. It’s just good mechanical construction.

## python – Selection of independent variables in K means clustering among a vast dataset

As I understand it, the process of K means clustering takes a set of sample points with k arbitrary centroids and uses Euclidean distance to classify the points closest to centroids to k groups.

What I am unable to understand is a point in the cartesian plane has only an x and y coordinate and so, amongst a given dataset we can only chose 2 independent variables and plot the points and proceed with the algorithm. However, there might be many more independent variables which could influence classification, for example, if we are trying to classify dogs based on their breeds using physical attributes such as size of ears, radius of eyes, body weight, length of legs, lifespan and so on. I’m not sure how this problem is resolved in K clustering.

Are the two variables with maximum information gain considered or are the points plotted in an n-dimensional space where each axis defines each attribute.

Could someone provide clarity on this issue. Thanks for any help

## What does "Memory of 128K by 9" means?

This is probably a very stupid question but I couldn’t find an answer anywhere. I’m reading the Technical Reference book of the IBM PC XT and it says that "The system board also has from 128K by 9 to 256K by 9 of R/W memory." What does this by 9 means?

## What Means the Final Option in Bump Fee / Increase Fee Electrum Wallet Option

Hello I want to know what will happen if i put my transaction as Final can saves fee or no?

## statistics – Is it possible to conclude that the mean of a set is greater than the mean of another set based on means of subsets?

Problem 8 of Chapter 2 in Sheldon M. Ross’ 5th edition of Introduction to probability and statistics for engineers and scientists is worded as follows:

The sample mean of the weights of the adult women of town A is larger than the sample mean of the weights of the adult women of town B. Moreover, the sample mean of the weights of the adult men of town A is larger than the sample mean of the weights of the adult men of town B. Can we conclude that the sample mean of the weights of the adults of town A is larger than the sample mean of the weights of the adults of town B? Explain your answer.

I tried to describe the problem as precisely as possible in algebraic terms. Here is the description I wrote:

Given:

$$bar x_{w,A}>bar x_{w,B} tag{1}$$
$$bar x_{m,A}>bar x_{m,B} tag{2}$$
$$sum_{i=1}^{n_{w,A}}x_{w,A,i} tag{1}$$
Where $$bar x_{w,A} = frac{sum_{i=1}^{n_{w,A}} x_{w,A,i}}{n_{w,A}} tag{3}$$
$$bar x_{w,B} = frac{sum_{i=1}^{n_{w,B}} x_{w,B,i}}{n_{w,B}} tag{4}$$
$$bar x_{m,A} = frac{sum_{i=1}^{n_{m,A}} x_{m,A,i}}{n_{m,A}} tag{5}$$
$$bar x_{m,B} = frac{sum_{i=1}^{n_{m,B}} x_{m,B,i}}{n_{m,B}} tag{6}$$

Can we conclude that $$bar x_A > bar x_B$$?

Where $$bar x_A = frac {sum_{i=1}^{n_{w,A}} x_{w,A,i} + sum_{i=1}^{n_{m,A}} x_{m,A,i}}{n_{w,A}+n_{m,A}} tag{7}$$

$$bar x_B = frac {sum_{i=1}^{n_{w,B}} x_{w,B,i} + sum_{i=1}^{n_{m,B}} x_{m,B,i}}{n_{w,B}+n_{m,B}} tag{8}$$

My first intuition was to rearrange (3) and (4) into (9) and (10):

$$bar x_{w, A} n_{w, A} = sum_{i=1}^{n_{w,A}}x_{w,A,i} tag {9}$$
$$bar x_{w, B} n_{w, B} = sum_{i=1}^{n_{w,B}}x_{w,B,i} tag {10}$$

Substituting (9) into (7) and (10) into (8) results in the following:

$$bar x_A = frac{bar x_{w,A}n_{w,A} + bar x_{m,A}n_{m,A}}{n_{w,A}+n_{m,A}}$$
$$bar x_B = frac{bar x_{w,B}n_{w,B} + bar x_{m,B}n_{m,B}}{n_{w,B}+n_{m,B}}$$

I am basically stuck here. How do I formally show whether we can conclude that $$bar x_A > bar x_B$$? How can I turn this into a formal mathematical proof?

## database – What are the means to which one can optimize key-value pairing in SQLITE?

Being holistically unfamiliar with the inner-workings and development history of SQL, I have to imagine that there are various strategies to optimize SQLITE in regards to key-value pairing. ( This is what I am primarily concerned with )

In researching the topic, I came across this white paper about SQLITE4 which is no longer being developed. SQLITE4 seemed to have a particular interest in optimizing itself for Key-Value Pairs.

https://www.sqlite.org/src4/doc/trunk/www/design.wiki

Some take-aways I took from it:

An instance of an sqlite4_env object defines how SQLite4 interacts with the rest of the system. An sqlite4_env object includes methods to:
access and control the underlying key/value storage engines,

The default built-in storage engine is a log-structured merge database. It is very fast, faster than LevelDB, supports nested transactions, and stores all content in a single disk file. Future versions of SQLite4 might also include a built-in B-Tree storage engine.

The PRIMARY KEY Is The Real Primary Key

SQLite3 allows one to declare any column or columns of a table to be the primary key. But internally, SQLite3 simply treats that PRIMARY KEY as a UNIQUE constraint. The actual key used for storage in SQLite is the rowid associated with each row.

SQLite4, on the other hand, actually uses the declared PRIMARY KEY of a table (or, more precisely, an encoding of the PRIMARY KEY value) as the key into the storage engine.

It has been stated that various lessons were learned from SQLITE4 and merged into SQLITE3, and I would like to know in addition what of the above, still applies?
Namely:

1. Can one access and control the underlying key/value storage engines in SQLITE?
2. Is there a B-Tree storage engine? Does it provide better write speeds?
3. Is the Primary Key now, the “Real primary key”?
4. If any of the previous questions ring true, what are the means these provide means to which one can optimize SQLITE for key-value pairs?

In addition, discussing the topic writ large, it has been suggested in private to me that

1. Smaller files provide better write speeds.
2. Paths to files are vastly faster than storing file data.
3. Key Types will impact lookups.
4. Reads can be accessed in multiple threads, however all writes should be delegated to one thread.

I would like to know if any of this is true.

Finally and most generally, are there any means not yet covered that one can utilize to optimize key value pairing? And more cynically; is this even a topic that warrants discussion, implying that any attempt to optimize is going to be superfluous?

Thanks.