Properizeis in the Property Management Tech Industry

Properize

By now, most of us are accustomed to using CSS Custom Properties on projects. Since its introduction in 2017, CSS Custom Properties, also known as CSS variables, have optimised the code we work with and allowed engineers a finer degree of control when managing values within rules. CSS Custom Properties can be tricky to deal with and aren’t always as intuitive as one might hope. However, when used right, they can significantly reduce boilerplate code and keep things efficient, making our work more productive. While the approach below is not perfect, it works well when writing CSS for building projects. Why Use CSS Custom Properties As far as my experience goes, I can only think of three possible reasons to implement a CSS Variable: We want to use a given value in more than one place,


We know that a value will change in the future and want to reduce our efforts for refactoring,


We need to store dynamic values from JS execution. With this in mind, we can be more assertive about our use cases. Point 3 is less of a concern for this article, but points 1 and 2 are essential. Let's illustrate this using the familiar HTML button element. The Infamous Button Buttons are notoriously tricky to style consistently for such a simple HTML element. Perhaps it’s because they have several different states and applications, regardless - it's usually the first component we Frontend Engineers take on when it comes to a fresh build. Let's have a look at how we could write the style for a button using CSS Custom Properties: :root {
 --color-primary: purple;
 --color-text: black;
 --color-text-inverted: white;
 --color-border: gray;
}

.button {
 --button-bg: var(--color-primary);
 --button-color: var(--color-text-inverted);
 --button-border: var(--color-border);

 align-items: center;
 background-color: var(--button-bg);
 border: 1px solid var(--button-border);
 color: var(--button-color);
 display: inline-flex;
 line-height: 1;
} As far as this example goes, from a technical standpoint, it’s great. It’s clean and straightforward and would get a 👍 from me in a code review. But could we optimise it further? Well, yes. The var() function in CSS is pretty nifty…we’re used to using it in a somewhat one-dimensional way by just rendering out a value; however, it can be more dynamic. The way to do this is by using a fallback value. If we considered the above example, we could rewrite it like so: :root {
 --color-primary: purple;
 --color-text: black;
 --color-text-inverted: white;
 --color-border: gray;
}

.button {
  align-items: center;
  background-color: var(--button-bg, var(--color-primary));
  border: 2px solid var(--button-border, var(--color-border));
  color: var(--button-color, var(--color-text-inverted));
  cursor: pointer;
  display: inline-flex;
  line-height: 1;
  padding-block: 0.875rem;
  padding-inline: 1rem;
} This is far cleaner and will lead to the same outcomes as the previous example - with less boilerplate code. Overriding it in a variation makes each locally scoped CSS Variable (effectively) optional. We can easily now optionally define the variables defined in .button as separate variations: .button:where(.button-secondary) {
  --button-bg: orange;
  --button-border: teal;
}

.button:where(.button-tertiary) {
  --button-bg: teal;
  --button-border: orange;
} Although this technique is not revolutionary, we care how many lines of compressed text are heading over the wire. The less physical memory a CSS file takes up, the better, which ultimately translates to how many lines of CSS exist. In the first example, we’re looking at almost double the amount of code to achieve the same thing in our optimised example. This compound effect has an influential impact on performance and further improves readability and developer experience. If you'd like to play around a bit further, feel free to fork the following Code Pen: https://codepen.io/iamdainemawer/pen/NWmQZMz Support Since April 2017, according to Google Baseline, this feature is well-supported across all major browsers. If you're interested to learn more about Baseline, read my post about Google Baseline and Its Impact You can check for browser support by adding the following statement to your CSS stylesheets: @supports(--css: variable) {} Can I Use - CSS Nesting
CSS Specification - CSS Nesting Module Resources MDN - CSS Custom Properties
CSS Variables Polyfill By now, most of us are accustomed to using CSS Custom Properties on projects. Since its introduction in 2017, CSS Custom Properties, also known as CSS variables, have optimised the code we work with and allowed engineers a finer degree of control when managing values within rules. CSS Custom Properties can be tricky to deal with and aren’t always as intuitive as one might hope. However, when used right, they can significantly reduce boilerplate code and keep things efficient, making our work more productive. While the approach below is not perfect, it works well when writing CSS for building projects. Why Use CSS Custom Properties As far as my experience goes, I can only think of three possible reasons to implement a CSS Variable: We want to use a given value in more than one place, We know that a value will change in the future and want to reduce our efforts for refactoring, We need to store dynamic values from JS execution. We want to use a given value in more than one place, We want to use a given value in more than one place, We know that a value will change in the future and want to reduce our efforts for refactoring, We know that a value will change in the future and want to reduce our efforts for refactoring, We need to store dynamic values from JS execution. We need to store dynamic values from JS execution. With this in mind, we can be more assertive about our use cases. Point 3 is less of a concern for this article, but points 1 and 2 are essential. Let's illustrate this using the familiar HTML button element. The Infamous Button Buttons are notoriously tricky to style consistently for such a simple HTML element. Perhaps it’s because they have several different states and applications, regardless - it's usually the first component we Frontend Engineers take on when it comes to a fresh build. Let's have a look at how we could write the style for a button using CSS Custom Properties: :root {
 --color-primary: purple;
 --color-text: black;
 --color-text-inverted: white;
 --color-border: gray;
}

.button {
 --button-bg: var(--color-primary);
 --button-color: var(--color-text-inverted);
 --button-border: var(--color-border);

 align-items: center;
 background-color: var(--button-bg);
 border: 1px solid var(--button-border);
 color: var(--button-color);
 display: inline-flex;
 line-height: 1;
} :root {
 --color-primary: purple;
 --color-text: black;
 --color-text-inverted: white;
 --color-border: gray;
}

.button {
 --button-bg: var(--color-primary);
 --button-color: var(--color-text-inverted);
 --button-border: var(--color-border);

 align-items: center;
 background-color: var(--button-bg);
 border: 1px solid var(--button-border);
 color: var(--button-color);
 display: inline-flex;
 line-height: 1;
} As far as this example goes, from a technical standpoint, it’s great. It’s clean and straightforward and would get a 👍 from me in a code review. But could we optimise it further? Well, yes. The var() function in CSS is pretty nifty…we’re used to using it in a somewhat one-dimensional way by just rendering out a value; however, it can be more dynamic. The way to do this is by using a fallback value . var() fallback value If we considered the above example, we could rewrite it like so: :root {
 --color-primary: purple;
 --color-text: black;
 --color-text-inverted: white;
 --color-border: gray;
}

.button {
  align-items: center;
  background-color: var(--button-bg, var(--color-primary));
  border: 2px solid var(--button-border, var(--color-border));
  color: var(--button-color, var(--color-text-inverted));
  cursor: pointer;
  display: inline-flex;
  line-height: 1;
  padding-block: 0.875rem;
  padding-inline: 1rem;
} :root {
 --color-primary: purple;
 --color-text: black;
 --color-text-inverted: white;
 --color-border: gray;
}

.button {
  align-items: center;
  background-color: var(--button-bg, var(--color-primary));
  border: 2px solid var(--button-border, var(--color-border));
  color: var(--button-color, var(--color-text-inverted));
  cursor: pointer;
  display: inline-flex;
  line-height: 1;
  padding-block: 0.875rem;
  padding-inline: 1rem;
} This is far cleaner and will lead to the same outcomes as the previous example - with less boilerplate code. Overriding it in a variation makes each locally scoped CSS Variable (effectively) optional. We can easily now optionally define the variables defined in .button as separate variations: .button:where(.button-secondary) {
  --button-bg: orange;
  --button-border: teal;
}

.button:where(.button-tertiary) {
  --button-bg: teal;
  --button-border: orange;
} .button:where(.button-secondary) {
  --button-bg: orange;
  --button-border: teal;
}

.button:where(.button-tertiary) {
  --button-bg: teal;
  --button-border: orange;
} Although this technique is not revolutionary, we care how many lines of compressed text are heading over the wire. The less physical memory a CSS file takes up, the better, which ultimately translates to how many lines of CSS exist. In the first example, we’re looking at almost double the amount of code to achieve the same thing in our optimised example. This compound effect has an influential impact on performance and further improves readability and developer experience. If you'd like to play around a bit further, feel free to fork the following Code Pen: https://codepen.io/iamdainemawer/pen/NWmQZMz https://codepen.io/iamdainemawer/pen/NWmQZMz Support Since April 2017, according to Google Baseline , this feature is well-supported across all major browsers. If you're interested to learn more about Baseline, read my post about Google Baseline and Its Impact Google Baseline Google Baseline and Its Impact You can check for browser support by adding the following statement to your CSS stylesheets: @supports(--css: variable) {} @supports(--css: variable) {} Can I Use - CSS Nesting CSS Specification - CSS Nesting Module Can I Use - CSS Nesting Can I Use - CSS Nesting CSS Specification - CSS Nesting Module CSS Specification - CSS Nesting Module Resources MDN - CSS Custom Properties CSS Variables Polyfill MDN - CSS Custom Properties MDN - CSS Custom Properties CSS Variables Polyfill CSS Variables Polyfill

Using CSS Custom Properties To Optimize Styling Efficiency and Readability

In a significant move that is contributing to the evolution of real estate investment, Libertum is thrilled to announce a collaboration with Tulum Land and Properties. This partnership punctuates the end of the traditional approach to real estate investment in the Tulum region of Mexico. The partnership represents an evolution to an era where property tokenization is the norm. It is appropriate that the vibrant real estate scene of Tulum, Mexico, known for its stunning properties and burgeoning market potential, will now also be recognized as a place where real estate tokenization is a reality. Tulum Land and Properties and Libertum are set to introduce a new era of investment opportunities by tokenizing a unique collection of villas with an initial portfolio of 300 million dollars. This innovative venture offers forward-thinking investors a unique chance to be part of Tulum's flourishing real estate sector, positioning it as a prime location for progressive investment. Javvad Azam, CEO at Libertum, said: "Tulum's real estate market is at an inflection point, observed with increasing interest from global investors. Our collaboration with Tulum Land and Properties is not just about introducing groundbreaking investment opportunities; it’s about crafting a legacy in one of the most mesmerizing destinations in the world.” The collaboration is timely, as Tulum continues to capture the attention of international investors and enthusiasts, with property values in the area poised for significant growth. Engaging in this venture allows investors to secure their stake in what is predicted to be a lucrative market, leveraging the expertise and insight of both Libertum and Tulum Land and Properties. Furthermore, this partnership harbors the potential to assist Libertum, paving the way for expansion beyond Tulum into Cancun and further exploration of the captivating lands of Mexico. This strategic move underlines Libertum's commitment to fostering growth and expanding its footprint in the international real estate market. Be part of this extraordinary journey with Libertum and Tulum Land and Properties. For a closer look at the unique area and to explore the opportunities this collaboration will create, you are encouraged to visit www.tulumlandandproperty.com and www.libertum.io This is more than an invitation to invest; it's a call to be part of an industry evolution that is now inevitable. About Libertum Libertum offers a complete infrastructure for real estate companies, property owners, agencies, and other RWA projects to tokenize assets. From digitizing rental income to ownership transfers through DAO, Libertum caters to all your on-chain real estate requirements. List properties, trade tokens, borrow via our lending protocol or reserve on-chain properties for a smooth experience. About Tulum Land and Properties For over four thrilling years, Tulum Land & Property (TLAP) has been at the forefront of Tulum's dynamic real estate market, offering unparalleled consultancy and brokerage services specifically designed for international investors. This story was distributed under HackerNoon’s Business Blogging Program. Learn more about the program here: https://business.hackernoon.com/ In a significant move that is contributing to the evolution of real estate investment, Libertum is thrilled to announce a collaboration with Tulum Land and Properties. This partnership punctuates the end of the traditional approach to real estate investment in the Tulum region of Mexico. The partnership represents an evolution to an era where property tokenization is the norm. It is appropriate that the vibrant real estate scene of Tulum, Mexico, known for its stunning properties and burgeoning market potential, will now also be recognized as a place where real estate tokenization is a reality. Tulum Land and Properties and Libertum are set to introduce a new era of investment opportunities by tokenizing a unique collection of villas with an initial portfolio of 300 million dollars. This innovative venture offers forward-thinking investors a unique chance to be part of Tulum's flourishing real estate sector, positioning it as a prime location for progressive investment. Javvad Azam, CEO at Libertum, said: "Tulum's real estate market is at an inflection point, observed with increasing interest from global investors. Our collaboration with Tulum Land and Properties is not just about introducing groundbreaking investment opportunities; it’s about crafting a legacy in one of the most mesmerizing destinations in the world.” "Tulum's real estate market is at an inflection point, observed with increasing interest from global investors. Our collaboration with Tulum Land and Properties is not just about introducing groundbreaking investment opportunities; it’s about crafting a legacy in one of the most mesmerizing destinations in the world.” The collaboration is timely, as Tulum continues to capture the attention of international investors and enthusiasts, with property values in the area poised for significant growth. Engaging in this venture allows investors to secure their stake in what is predicted to be a lucrative market, leveraging the expertise and insight of both Libertum and Tulum Land and Properties. Furthermore, this partnership harbors the potential to assist Libertum, paving the way for expansion beyond Tulum into Cancun and further exploration of the captivating lands of Mexico. This strategic move underlines Libertum's commitment to fostering growth and expanding its footprint in the international real estate market. Be part of this extraordinary journey with Libertum and Tulum Land and Properties. For a closer look at the unique area and to explore the opportunities this collaboration will create, you are encouraged to visit www.tulumlandandproperty.com and www.libertum.io www.libertum.io www.libertum.io This is more than an invitation to invest; it's a call to be part of an industry evolution that is now inevitable. About Libertum Libertum offers a complete infrastructure for real estate companies, property owners, agencies, and other RWA projects to tokenize assets. From digitizing rental income to ownership transfers through DAO, Libertum caters to all your on-chain real estate requirements. List properties, trade tokens, borrow via our lending protocol or reserve on-chain properties for a smooth experience. Libertum About Tulum Land and Properties For over four thrilling years, Tulum Land & Property (TLAP) has been at the forefront of Tulum's dynamic real estate market, offering unparalleled consultancy and brokerage services specifically designed for international investors. Tulum Land & Property (TLAP) This story was distributed under HackerNoon’s Business Blogging Program. Learn more about the program here: https://business.hackernoon.com/ This story was distributed under HackerNoon’s Business Blogging Program. Learn more about the program here: https://business.hackernoon.com/ https://business.hackernoon.com/

Libertum Announces Strategic Collaboration with Tulum Land & Properties to Revolutionize Real Estate

Libertum রিয়েল এস্টেট বিপ্লব করতে Tulum জমি এবং সম্পত্তির সাথে কৌশলগত সহযোগিতা ঘোষণা করেছে

Libertum kündigt strategische Zusammenarbeit mit Tulum Land & Properties an, um den Immobilienmarkt zu revolutionieren

Libertum anuncia colaboración estratégica con Tulum Land & Properties para revolucionar el sector inmobiliario

Libertum annonce une collaboration stratégique avec Tulum Land & Properties pour révolutionner l'immobilier

लिबर्टम ने रियल एस्टेट में क्रांति लाने के लिए टुलम लैंड एंड प्रॉपर्टीज़ के साथ रणनीतिक सहयोग की घोषणा की

リバタム、不動産業界に革命を起こすためトゥルム・ランド＆プロパティーズとの戦略的提携を発表

Libertum, 부동산 혁명을 위해 Tulum Land & Properties와의 전략적 협력 발표

Libertum anuncia colaboração estratégica com Tulum Land & Properties para revolucionar o mercado imobiliário

Libertum объявляет о стратегическом сотрудничестве с Tulum Land & Properties, чтобы произвести революцию в сфере недвижимости

Libertum, Gayrimenkulde Devrim Yaratmak İçin Tulum Land & Properties ile Stratejik İşbirliği Duyurdu

Libertum công bố hợp tác chiến lược với Tulum Land & Properties để cách mạng hóa bất động sản

Libertum 宣布与 Tulum Land & Properties 开展战略合作，共同革新房地产

https://www.youtube.com/watch?v=5t1vTLU7s40&embedable=true&transcript=true&long=true

Yann Lecun on "The Danger in the Concentration of Power Through Proprietary AI Systems" 

ইয়ান লেকুন "মালিকানা AI সিস্টেমের মাধ্যমে শক্তির ঘনত্বে বিপদ"

Yann Lecun über „Die Gefahr der Machtkonzentration durch proprietäre KI-Systeme“

Yann Lecun sobre "El peligro de la concentración de poder a través de sistemas propietarios de IA"

Yann Lecun sur "Le danger de la concentration du pouvoir via des systèmes d'IA propriétaires"

यान लेकुन "मालिकाना एआई सिस्टम के माध्यम से शक्ति की एकाग्रता में खतरा" पर

ヤン・レクン氏「独自の AI システムを通じた権力集中の危険性」について

Yann Lecun의 "전용 AI 시스템을 통한 권력 집중의 위험성"

Yann Lecun sobre "O perigo na concentração de poder por meio de sistemas proprietários de IA"

Янн Лекун об «Опасности концентрации власти посредством запатентованных систем искусственного интеллекта»

Yann Lecun, "Tescilli Yapay Zeka Sistemleri Yoluyla Gücün Yoğunlaşmasının Tehlikesi" hakkında konuşuyor

Yann Lecun về "Mối nguy hiểm của việc tập trung quyền lực thông qua các hệ thống AI độc quyền"

Yann Lecun 谈“专有 AI 系统权力集中的危险”

You join independent information TL;DR: Don't mix ortoghonal behavior Problems Maintainability Error Prone Performance Penalties Premature optimization principle violation The principle of least astonishment Violation Bijection Duplication of Logic on breaking the attributes Coupling Solutions Break Orthogonal behavior and properties Context Parsing data is always a problem, where joining elements is much easier than breaking them. If you use a separator to break the attributes, you need to make sure the separator does not belong to the domain, and you should escape it. If you map your data to relational databases, search queries will be more difficult and less performant for concatenated attributes. Sample Code Wrong class Point {
    constructor(coordString) {
        this.coordString = coordString;
    }

    x() {
        const coords = this.coordString.split(',');
        if (coords.length !== 2) {
            throw new Error('Invalid coordinate string format');
        }
        return parseFloat(coords[0]);
    }

    y() {
        const coords = this.coordString.split(',');
        if (coords.length !== 2) {
            throw new Error('Invalid coordinate string format');
        }
        return parseFloat(coords[1]);
    }
} Right class Point {
    constructor(x, y) {
        this.x = x;
        this.y = y;
    }
} Detection Semi-Automatic [x] This is a semantic smell, but you can find suspicious concatenation actions on peer reviews. Tags Coupling Level Beginner [x] AI Assistants AI Assistants don't usually suggest this kind of premature optimization of bad rules. Conclusion Don't mix unrelated things since breaking things is always harder than having them separated. Relations Code Smell 20 - Premature Optimization Disclaimer Code Smells are my . opinion Credits Photo by on Tomas Sobek Unsplash Design is choosing how you will fail. Ron Fein Software Engineering Great Quotes This article is part of the CodeSmell Series. How to Find the Stinky Parts of your Code

Code Smell 243 - Concatenated Properties

This paper is available on arxiv under CC BY-NC-SA 4.0 DEED license. Authors: (1) Pascal Baumann, Max Planck Institute for Software Systems (MPI-SWS), Germany; (2) Rupak Majumdar, Max Planck Institute for Software Systems (MPI-SWS), Germany; (3) Ramanathan S. Thinniyam, Max Planck Institute for Software Systems (MPI-SWS), Germany; (4) Georg Zetzsche, Max Planck Institute for Software Systems (MPI-SWS), Germany. Table of Links Introduction Dynamic Networks of Concurret Pushdown Systems (DCPS) Warm-up: Non-Termination Fair Non-Termination From Progressive Runs for VASSB to Reachability Starvation Conclusion, Acknowledgment & References A. Strengthening Fairness to Progressive Runs B. Proofs from Section 4.1 C. Proofs for Section 5 D. Proofs for Section 5.3 E. Proofs for Section 6 We study context-bounded verification of liveness properties of multi-threaded, shared-memory programs, where each thread can spawn additional threads. Our main result shows that context-bounded fair termination is decidable for the model; context-bounded implies that each spawned thread can be context switched a fixed constant number of times. Our proof is technical, since fair termination requires reasoning about the composition of unboundedly many threads each with unboundedly large stacks. In fact, techniques for related problems, which depend crucially on replacing the pushdown threads with finite-state threads, are not applicable. Instead, we introduce an extension of vector addition systems with states (VASS), called VASS with balloons (VASSB), as an intermediate model; it is an infinite-state model of independent interest. A VASSB allows tokens that are themselves markings (balloons). We show that context bounded fair termination reduces to fair termination for VASSB. We show the latter problem is decidable by showing a series of reductions: from fair termination to configuration reachability for VASSB and thence to the reachability problem for VASS. For a lower bound, fair termination is known to be non-elementary already in the special case where threads run to completion (no context switches). We also show that the simpler problem of context-bounded termination is 2EXPSPACE-complete, matching the complexity bound—and indeed the techniques—for safety verification. Additionally, we show the related problem of fair starvation, which checks if some thread can be starved along a fair run, is also decidable in the context-bounded case. The decidability employs an intricate reduction from fair starvation to fair termination. Like fair termination, this problem is also non-elementary. 1 INTRODUCTION We study decision problems related to liveness verification of shared-memory multithreaded programs. In a shared-memory multithreaded program, a number of threads execute concurrently. Each thread executes possibly recursive sequential code, and can spawn new threads for concurrent execution. The threads communicate through shared global variables that they can read and write. The execution of the program is guided by a non-deterministic scheduler that picks one of the spawned threads to execute in each time step. If the scheduler replaces the currently executing thread with a different one, we say the current active thread is context switched. Shared-memory multithreaded programming is ubiquitous and static verification of safety or liveness properties of such programs is a cornerstone of formal verification research. Indeed, there is a vast research literature on the problem—from a foundational understanding of the computability and complexity of (subclasses of) models, to program logics, and to efficient tools for analysis of real systems. In this paper, we focus on decidability issues for liveness verification for multithreaded shared memory programs with the ability to spawn threads. Liveness properties, intuitively, specify that “something good” happens when a program executes. A simple example of a liveness property is termination: the property that a program eventually terminates. In fact, termination is a “canonical” liveness property: for a very general class of liveness properties, through monitor constructions, verifying liveness properties reduces to verifying termination [Apt and Olderog 1991; Vardi 1991]. Unfortunately, under the usual notion of non-deterministic schedulers, some programs may fail to terminate for uninteresting reasons. Consider the following program: 1 global bit := 1; 2 main () { spawn foo ; spawn bar ; } 3 foo () { if bit = 1 then spawn foo ; } 4 bar () { bit := 0; } A main thread spawns two additional threads foo and bar. The thread foo checks if a global bit is set and, if so, re-spawns itself. The thread bar resets the global bit. There is a non-terminating execution of this program in which bar is never scheduled. However, a scheduler that never schedules a thread that is ready to run would be considered unfair. Instead, one formulates the problem of fair termination: termination under a fair non-deterministic scheduler. We abstract away from the exact mechanism of the scheduler, and only require that every spawned thread that is infinitely often ready to run is eventually scheduled. Then, every fair run of the above program is terminating: eventually bar is scheduled, after which foo does not spawn a new thread. Since the high undecidability relies on an unbounded exchange of information among threads, a recent and apposite approach to verifying concurrent recursive programs is to explore only a representative subset of program behaviors by limiting the number of inter-thread interactions [Musuvathi and Qadeer 2007; Qadeer and Rehof 2005]. This approach, called context bounding by Qadeer and Rehof [2005], considers the verification problem as a family of problems, one for each K. The K-context bounded instance, for any fixed K ≥ 0, considers only those executions where each thread is context switched at most K times by the scheduler. In the limit as K → ∞, the K-bounded approach explores all behaviors where each thread runs a finite number of times. In practice, bounded explorations with small values of K have proved to be effective to uncover many safety and liveness bugs in real systems. Our results generalize the special case of K = 0 studied by Ganty and Majumdar [2012] as asynchronous programs. When K = 0, each thread executes to completion without being interrupted in the middle. Ganty and Majumdar show the decidability of safety and liveness verification for this model. In particular, they prove safety and termination are both EXPSPACE-complete and fair termination and fair starvation are decidable but non-elementary.[2] Their proof depends on the observation that, since threads are not interrupted, one can replace the pushdown automata for each thread by finite automata that accept Parikh-equivalent languages. Unfortunately, their technique does not generalize when context switches are allowed. For K ≥ 1, Atig et al. [2009] showed that the safety verification problem is decidable in 2EXPSPACE. Ten years later, a matching lower bound was shown by Baumann et al. [2020]. The key observation in the decision procedure is that safety is preserved under downward closures: one can analyze a related program where some spawned threads are “forgotten.” Since the downward closure of a context free language is effectively regular, one can replace the pushdown automaton for each thread by a finite automaton accepting the downward closure. In fact, our proof of termination also follows easily from this observation, as termination is also preserved by downward closures. Unfortunately, fair termination and fair non-starvation are not preserved under downward closures. Thus, we cannot apply the preceding techniques to replace pushdown automata by finite automata in our construction. Thus, our proof is more intricate and requires several insights into the computational model. The key difficulty in our decision procedure is to maintain a finite representation for unboundedly many active threads, each with unboundedly large local stacks and potentially spawning unboundedly many new threads, and to compose their context-switched executions into a global execution. In order to maintain and compose such configurations, we introduce a new model, called VASS with balloons (VASSB), that extends the usual model of a vector addition systems with states (VASS) with “balloons”: a token in a VASSB can be a usual VASS token or a balloon token that is itself a vector. Intuitively, balloon tokens represent the possible new threads a thread can spawn along one of its execution segments. We show through a series of constructions that the fair termination problem reduces to the fair termination problem for VASSB, and thence to the configuration reachability problem for VASSB. Finally, we show that configuration reachability for VASSB is decidable by a reduction to the reachability problem for VASS. This puts VASSB in the rare class of infinite-state systems which generalize VASS and yet maintain a decidable reachability (not just coverability!) problem. Finally, we show a reduction from the fair starvation problem to fair termination. The reduction relies on two combinatorial insights. The first is that if a program has an infinite fair run, then it has one in which there exists a bound on the number of threads spawned by each thread. The second is a novel pumping argument based on Ramsey’s theorem; it implies that it suffices to track a finite amount of data about each thread to determine whether some thread can be starved. In conclusion, we prove decidability of liveness verification for multithreaded shared memory programs with the ability to dynamically spawn threads, an extremely expressive model of multithreaded programming. This model sits at the boundary of decidability and subsumes many other models studied before. Safety verification for concurrent recursive programs is already undecidable with just two threads and finite global store [Ramalingam 2000]. Many results on context-bounded safety verification consider a model with a fixed number of threads, without spawns. The complexity of safety verification for this model is well understood at this point. The key idea underlying the best algorithms reduce the problem to analyzing a sequential pushdown system [Lal and Reps 2009] by guessing the bounded sequences of context switches for each thread and using the finite state to ensure the sequential runs can be stitched together Related Work. When the model allows spawning of new threads, as ours does, existing decision procedures are significantly more complex, both in their technicalities and in computational cost. There are relatively few results on decidability of liveness properties of infinite-state systems. Atig et al. [2012a] show a sufficient condition for fair termination for context-bounded executions of a fixed number of threads, where they look for ultimately periodic executions, in which each thread is context switched at most K times in the loop. They show that the search for such ultimately periodic executions can be reduced to safety verification. In our model, fair infinite runs may involve unboundedly many threads with unbounded stacks and need not be periodic—for example, there can always be more and more newly spawned threads. Multi-pushdown systems model multithreaded programs with a fixed number of threads. Many decision procedures are known when the executions of such systems are restricted through different bounds such as context, scope, or phase [Atig et al. 2012b, 2017; Torre et al. 2016], and also through limitations on communication patterns [Lal et al. 2008]. These problems are orthogonal to us, either in the modeling capabilities or in the properties verified. Decidability of linear temporal logic is known for weaker models of multithreaded recursive programs, such as symmetric parameterized programs [Kahlon 2008] or leader-follower programs with non-atomic reads and writes [Durand-Gasselin et al. 2017; Fortin et al. 2017; Muscholl et al. 2017]. These programs cannot perform compare-and-swap operations, and therefore, their computational power is quite limited (in fact, LTL model checking is PSPACE-complete). A number of heuristic approaches to fair termination of multithreaded programs provide sound but incomplete algorithms, but for a more general class of programs involving infinite-state data variables [Cook et al. 2007, 2011; Farzan et al. 2016; Kragl et al. 2020; Padon et al. 2018]. The goal there is to provide a sound proof rule for verification but not to prove a decidability result. In terms of fair termination problems for VASS, the theme of computational hardness continues. For example, the classical notion of fair runs, in which an infinitely activated transition has to be fired infinitely often, leads to undecidability [Carstensen 1987] and even Σ 1 1 - completeness [Howell et al. 1991]. However, weakly fair termination, where only those transitions that are almost always activated have to be fired infinitely often, is decidable [Jančar 1990]. A rich taxonomy of fairness notions with corresponding decidability results can be found in [Howell et al. 1991]. However, all of these notions appear to be incomparable with our fairness notion for VASSB. Our model of VASSB treads the boundary of models that generalize VASS for which reachability can be proved to be decidable. We note that there are several closely related models, VASS with a stack [Leroux et al. 2015] and branching VASS [Verma and Goubault-Larrecq 2005], for which decidability of reachability is a long-standing open problem, and others, nested Petri nets [Lomazova and Schnoebelen 1999], for which reachability is undecidable. [1] Recall that the class Π 1 1 in the analytic hierarchy is the class of all relations on N that can be defined by a universal second-order number-theoretic formula. [2] Their result shows a polynomial-time equivalence between fair termination and reachability in vector addition systems with states (VASS, a.k.a. Petri nets). The complexity bounds follow from our current knowledge of the complexity of VASS reachability [Czerwinski et al. 2019].

Context-Bounded Verification of Liveness Properties for
Multithreaded Shared-Memory Programs: Intro

Custom properties have been a pretty big deal for us, who use regularly. Many of us are probably starting to use them quite a bit, especially as part of a color or theming system. They really work great for this. But what about when we need alpha transparency for a color set with a custom property? Well, in this post, I’ll show you how it works. Alright, let’s check it out! CSS https://youtu.be/RduB0gmxsxM?embedable=true Here, in this example, we have this title. Currently, it’s just using the color red to give it its color. h1 {
    color: red;
} Creating and Using a Basic CSS Custom Property for a Color Value Let’s say we’re converting over to use custom properties for our colors in order to make it easier to change the overall theme when needed. In our theme, red will be our primary color, so in our element, we’ll create a custom property called “primary.” html html {
    --primary: red;
} Now, we’ll switch our to use this primary custom property. h1 h1 {
    color: var(--primary);
} There we go. Now, what if we need to use this custom property with the color function so that we can change the opacity? Can this be done? Well, let’s find out. Let’s wrap our custom property in the color function. rgba() rgba() h1 {
    color: rgba(var(--primary));
} Ugh, bummer, it looks like that doesn’t work for us. Using the CSS rgba() Color Function With a Custom Property The good news is that it is possible though. We can actually use custom properties with the color function if the property is set to an value. So, this means we just need to add a custom property that is set to the value of red. rgba() rgb rgb Let’s add a new property called “primary-rgb”. And we’ll set it to two fifty-five, zero, zero. html {
    ...
    --primary-rgb: 255, 0, 0;
} Now, let’s add another header to make them easier to compare. <div>
    <h1>Change My Color</h1>
    <h1>I'm Using RGBA</h1>
</div> And, on our second header, we’ll use the color function, then inside, we’ll use our new primary custom property, and let’s give it an alpha value of point five. rgba() rgb h1:last-child {
    color: rgba(var(--primary-rgb), 0.5);
} And there we go; now it works. So, in order to use the color function with custom properties all we need to do is start with values. rgba() rgb Want to See It in Action? Check out the demo code and examples of these techniques in the Codepen example below. If you have any questions or thoughts, don’t hesitate to leave a comment. https://codepen.io/brianmtreese/pen/qBgoapN?embedable=true Also published . here

Alpha Transparency in CSS Custom Properties

Steam, Its Generation and Use by Babcock & Wilcox Company, is part of the HackerNoon Books Series. You can jump to any chapter in this book . PROPERTIES OF AIR here PROPERTIES OF AIR Pure air is a mechanical mixture of oxygen and nitrogen. While different authorities give slightly varying values for the proportion of oxygen and nitrogen contained, the generally accepted values are: By volume, oxygen 20.91 per cent, nitrogen 79.09 per cent. By weight, oxygen 23.15 per cent, nitrogen 76.85 per cent. Air in nature always contains other constituents in varying amounts, such as dust, carbon dioxide, ozone and water vapor. Being perfectly elastic, the density or weight per unit of volume decreases in geometric progression with the altitude. This fact has a direct bearing in the proportioning of furnaces, flues and stacks at high altitudes, as will be shown later in the discussion of these subjects. The atmospheric pressures corresponding to various altitudes are given in . Table 12 The weight and volume of air depend upon the pressure and the temperature, as expressed by the formula: The weight of one cubic foot of air will obviously be the reciprocal of its volume, that is, 1/ pounds. v Example: Required the volume of air in cubic feet under 60.3 pounds gauge pressure per square inch at 115 degrees Fahrenheit. gives the weights and volumes of air under atmospheric pressure at varying temperatures. Table 27 Formula ( ) holds good for other gases with the change in the value of the constant as follows: 9 For oxygen 48.24, nitrogen 54.97, hydrogen 765.71. The specific heat of air at constant pressure varies with its temperature. A number of determinations of this value have been made and certain of those ordinarily accepted as most authentic are given in . Table 28 This value is of particular importance in waste heat work and it is regrettable that there is such a variation in the different experiments. Mallard and Le Chatelier determined values considerably higher than any given in . All things considered in view of the discrepancy of the values given, there appears to be as much ground for the use of a constant value for the specific heat of air at any temperature as for a variable value. Where this value is used throughout this book, it has been taken as 0.24. Table 28 Air may carry a considerable quantity of water vapor, which is frequently 3 per cent of the total weight. This fact is of importance in problems relating to heating drying and the compressing of air. gives the amount of vapor required to saturate air at different temperatures, its weight, expansive force, etc., and contains sufficient information for solving practically all problems of this sort that may arise. Table 29 About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Babcock & Wilcox Company (2007). Steam, Its Generation and Use. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/22657/pg22657-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at , located at . www.gutenberg.org https://www.gutenberg.org/policy/license.html

PROPERTIES OF AIR

Steam, Its Generation and Use by Babcock & Wilcox Company, is part of the HackerNoon Books Series. You can jump to any chapter in this book . PROPERTIES OF WATER here PROPERTIES OF WATER Pure water is a chemical compound of one volume of oxygen and two volumes of hydrogen, its chemical symbol being H 2 O. The weight of water depends upon its temperature. Its weight at four temperatures, much used in physical calculations, is given in . Table 10 While authorities differ as to the weight of water, the range of values given for 62 degrees Fahrenheit (the standard temperature ordinarily taken) being from 62.291 pounds to 62.360 pounds per cubic foot, the value 62.355 is generally accepted as the most accurate. A United States standard gallon holds 231 cubic inches and weighs, at 62 degrees Fahrenheit, approximately 8 1 ⁄ 3 pounds. A British Imperial gallon holds 277.42 cubic inches and weighs, at 62 degrees Fahrenheit, 10 pounds. The above are the true weights corrected for the effect of the buoyancy of the air, or the weight in vacuo . If water is weighed in air in the ordinary way, there is a correction of about one-eighth of one per cent which is usually negligible. Water is but slightly compressible and for all practical purposes may be considered non-compressible. The coefficient of compressibility ranges from 0.000040 to 0.000051 per atmosphere at ordinary temperatures, this coefficient decreasing as the temperature increases. gives the weight in vacuo and the relative volume of a cubic foot of distilled water at various temperatures. Table 11 The weight of water at the standard temperature being taken as 62.355 pounds per cubic foot, the pressure exerted by the column of water of any stated height, and conversely the height of any column required to produce a stated pressure, may be computed as follows: The pressure in pounds per square foot = 62.355 × height of column in feet. The pressure in pounds per square inch = 0.433 × height of column in feet. Height of column in feet = pressure in pounds per square foot ÷ 62.355. Height of column in feet = pressure in pounds per square inch ÷ 0.433. Height of column in inches = pressure in pounds per square inch × 27.71. Height of column in inches = pressure in ounces per square inch × 1.73. By a change in the weights given above, the pressure exerted and height of column may be computed for temperatures other than 62 degrees. A pressure of one pound per square inch is exerted by a column of water 2.3093 feet or 27.71 inches high at 62 degrees Fahrenheit. Water in its natural state is never found absolutely pure. In solvent power water has a greater range than any other liquid. For common salt, this is approximately a constant at all temperatures, while with such impurities as magnesium and sodium sulphates, this solvent power increases with an increase in temperature. Sea water contains on an average approximately 3.125 per cent of its weight of solid matter or a thirty-second part of the weight of the water and salt held in solution. The approximate composition of this solid matter will be: sodium chloride 76 per cent, magnesium chloride 10 per cent, magnesium sulphate 6 per cent, calcium sulphate 5 per cent, calcium carbonate 0.5 per cent, other substances 2.5 per cent. The boiling point of water decreases as the altitude above sea level increases. gives the variation in the boiling point with the altitude. Table 12 Water has a greater specific heat or heat-absorbing capacity than any other known substance (bromine and hydrogen excepted) and its specific heat is the basis for measurement of the capacity of heat absorption of all other substances. From the definition, the specific heat of water is the number of British thermal units required to raise one pound of water one degree. This specific heat varies with the temperature of the water. The generally accepted values are given in , which indicates the values as determined by Messrs. Marks and Davis and Mr. Peabody. Table 13 In consequence of this variation in specific heat, the variation in the heat of the liquid of the water at different temperatures is not a constant. gives the heat of the liquid in a pound of water at temperatures ranging from 32 to 340 degrees Fahrenheit. Table 22 [13] The specific heat of ice at 32 degrees is 0.463. The specific heat of saturated steam (ice and saturated steam representing the other forms in which water may exist), is something that is difficult to define in any way which will not be misleading. When no liquid is present the specific heat of saturated steam is negative. The use of the value of the specific heat of steam is practically limited to instances where superheat is present, and the specific heat of superheated steam is covered later in the book. [14] About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Babcock & Wilcox Company (2007). Steam, Its Generation and Use. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/22657/pg22657-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at , located at . www.gutenberg.org https://www.gutenberg.org/policy/license.html

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