## multithreading – Parallel map in Rust

A parallel map written in Rust. I am new to Rust and wondering if there is things that could be done better or more efficiently.

``````use crossbeam_channel::unbounded;

fn parallel_map<T, U, F>(mut input_vec: Vec<T>, num_threads: usize, f: F) -> Vec<U>
where
F: FnOnce(T) -> U + Send + Copy + 'static,
T: Send + 'static,
U: Send + 'static + Default,
{
let mut output_vec: Vec<U> = Vec::with_capacity(input_vec.len());

let (in_s, in_r) = unbounded::<(T, usize)>();
let (out_s, out_r) = unbounded::<(U, usize)>();

let in_r = in_r.clone();
let out_s = out_s.clone();
while let Ok((value, index)) = in_r.recv() {
let res = f(value);
out_s.send((res, index)).expect("Failed to send");
}
}));
}

while let Some(val) = input_vec.pop() {
in_s.send((val, input_vec.len())).expect("Failed to send");
}

drop(in_s);
drop(out_s);

let mut collect_results: Vec<(U, usize)> = Vec::with_capacity(output_vec.capacity());
while let Ok(res) = out_r.recv() {
collect_results.push(res);
}

collect_results.sort_by(|(_, a_index), (_, b_index)| a_index.partial_cmp(b_index).unwrap());

output_vec.extend(collect_results.into_iter().map(|(val, _)| val));

}

output_vec
}

fn main() {
let v = vec!(6, 7, 8, 9, 10, 1, 2, 3, 4, 5, 12, 18, 11, 5, 20);
let squares = parallel_map(v, 10, |num| {
println!("{} squared is {}", num, num * num);
num * num
});
println!("squares: {:?}", squares);
}
$$```$$
``````

## Define a unique linear map

Let $$L_1=left( begin{array}{cc} a & b \ c & d \ end{array} right)$$
$$L_1(1,2)=(0,-1)$$ means that $$(a+2 b,c+2 d)=(0,-1)$$

$$L_1(-1,1)=(2,1)to (b-a,d-c)=(2,1)$$

So we have the linear system
$$begin{cases} a+2b=0\ c+2d=-1\ b-a=2\ d-c=1\ end{cases}$$
which gives
$$a= -frac{4}{3},b= frac{2}{3},c= -1,d= 0$$
and finally
$$L_1=left( begin{array}{cc} -frac{4}{3} & frac{2}{3} \ -1 & 0 \ end{array} right)$$

## Evaluating \$k\$ order derivative of a composition map at some point \$t\$. Rudin 9.30.

The problem statment. Let $$fin C^m(E)$$, where $$E$$ is an open subset of $$Bbb{R^n}$$. Fix $$ain E$$, and suppose $$xin Bbb{R^n}$$ is so close to $$0$$ that the points $$p(t) a+ tx$$ lie in $$E$$ whenever $$1geq tgeq0$$. Define $$h(t)=f(p(t))$$ for all $$tin Bbb{R}$$ for which $$p(t)in E$$. Problem : For $$mgeq kgeq1$$, show that $$h^{(k)}(t)=sum(D_{i_1 …i_k}f)(p(t))x_{i_1}…x_{i_k}$$. The sum extends over all ordered k-tuples $$(i_1…i_k)$$ in which each $$i_j$$ is one of the integers $$1,…,n$$.

Using the chain rule repeatedly is recommended, so I computed $$h^{(1)}(t)=h'(t)=f'(p(t))cdotp p'(t)=sum_i^n(D_if)(p(t))cdot x_i$$

But then $$h^{(2)}=f”(p(t))cdot p”(t)=0.$$ It doesn’t seem like this kind of process will lead towards the answer. Suggestions?

## How to find all locations from a source point at Google Map?

Taking a scenario. I searched a location at https://www.google.com/maps/.

Taking the location as a centre, how to find all locations around the location within a radius of certain meter or kilometre?

With Regards
TekQ

## trains – List or map of publicly available wifi hotspots in Europe

Are there lists or map websites that show all widely known, publicly-provided wi-fi hotspots in continental Europe with free log in? By public, I mean non-civilian/private, such as state-endorsed (train stations) or heavily commercial (McDonalds hotspots). Country or city-specific maps would be a start too

## etcd – Kubernetes API: Compare and update config map key

Etcd has a concept of `Atomic Compare-and-Update` by comparing the key’s value before executing an update. I’d like to use this feature for updating a `ConfigMap` in my Kubernetes cluster. I’d like to update the config map only if the existing config map data or a specific data key matches a certain value.

Example ConfigMap:

``````curl -X POST -H 'Content-Type: application/json'
-d '{"apiVersion": "v1", "kind": "ConfigMap", "metadata": {"name": "test"}, "data": {"foo": "1"}}'
http://localhost:8001/api/v1/namespaces/default/configmaps
``````

I need to interact with K8S API or directly with K8S’s `etcd` directly if possible (is it?), and I don’t want to rely on `resourceVersion`. I’d like to depend on my own version which is actually the config map’s data key. How can I achieve such an atomic UPDATE (or DELETE) operation?

## user expectation – Can we create Empathy Map without creating Persona?

I am new to this UX industry. I have a task with a brief to create an Audiobook app experience & to map out and simply describe what will be your end-to-end design process to tackle this problem.

As of now I am not able to find out Prospective users to interview for this concept so , I’m thinking that I can create Empathy map by visualising as a User & move forward with User flow diagram.

So here are 2 questions:

1. What’s the best creating combination of Artefacts to describe End-to-end design process ? Like , Problem statement, Solution , Empathy map , user flow diagram , IA etc ?
2. Can I directly create Empathy map without creating Persona ?

Any help would be appreciated!

## ag.algebraic geometry – the map on divisor class groups induced by restriction to a toric subvariety

Let $$X$$ be a (say, complex) toric variety acted upon by a torus $$T$$ and defined by a fan $$Sigma$$ in the cocharacter lattice $$N=mathrm{Hom}(mathbb{C}^times, T)$$, and let $$M$$ be the character lattice. For any cone $$sigma in Sigma$$ put $$M(sigma) = sigma^perp cap M$$, $$N(sigma) = mathrm{Hom}(M(sigma), mathbb{C}^times)$$. There is a natural projection $$N to N(sigma)$$. Then the closure of the orbit corresponding to $$sigma$$ has the structure of a toric variety with respect to the quotient torus with the cocharacter lattice $$N/N(sigma)$$ and given by the fan $$Star(sigma)$$ consisting of the images in $$N(sigma)$$ of the cones of $$Sigma$$ containing $$sigma$$. Note that the closed embedding $$X_{Star(sigma)} to X$$ is generally not a toric morphism, since the dense toric orbit of $$X_{Star(sigma)}$$ does not intersect the dense toric orbit of $$X$$.

My question is: is there a way to describe the restriction map $$mathrm{Cl}(X) to mathrm{Cl}(X_{Star(sigma)})$$ in terms of the fans $$Sigma$$ and $$Star(sigma)$$?

## views – Choose location on a map and add to webform submission details – drupal 8

We’d like to be able to allow a user to pin point a location on a map and then be able store that information with lat and long in a webform submission.

I’ve looked into the add on’s on webform drupal 8 but there doesn’t seem to be any direct integrations to allow this to happen.

Looked into the geofield module with leaflet integration and it does what we want within a content type and allows content managers to choose a location, however, we’d like to get this working for drupal 8 webform. Any leads would be helpful.

## Colour scheme for two distinct sets of 5 items on a map

I apologize for the utter simplicity of this, but it is beyond me.

I am using a Leaflet and Leaflet.markercluster to add markers to a map. The latter helps resolve clutter by grouping icons near to each other, which would otherwise overlap.

As you can see from this screenshot, the more markers in a group, the darker – sort of, it runs from dark orange, through yellow to green (there are actually 5 levels). Visit the demo and zoom the map to see how it works.

So far, so good. I have implemented this in my app and when expanded to individual markers, they are either green or blue, with each having a specific meaning.

I also have different set of markers, which are read, and now there becoming enough of them to want to cluster them too.

The red marker is

with RGB value of #982E40 (I use the smaller marker). See here for all leaflet markers.

There are a total of five zoom levels, governed by CSS, depending on how “big” the group is (how many markers it represents).

Finally, a question: which RGB values, dark to light, should I use to represent the second set of circular cluster groups (notice that the circles actually have a darker centre, with a lighter surround) in order to distinguish them from the others.

I want to have two visually different groups of clusters. I am capable of making each group a single colour, no matter how markers it contains. I am not capable of making the five levels of each both distinct and visually appealing.

Hmmm, maybe I want to use that outer circle and make it either green or red, irrespective of the centre colour? Also, the default uses up to five colours; maybe that ought to be just 5 shades of green, to compare with 5 shades of red? Note,: I am not married to green & red (the existing groups represent companies and the new one will represent unemployed people).

Also, 2 colours might enough, as the clusters show how many markers they contain. I can see how colours relating to size might help, but might they also confuse?