If you’ve never used Dianping, think Yelp—but shinier, angrier, and far more dominating with the fate of restaurants in China. It’s the platform people turn to when deciding whether some ¥68 hotpot buffet would be a delicious meal or a strict no-no. Naturally, the platform holds immense power. A single low rating can haunt a restaurant’s prospects worse than bad feng shui. Restaurants, understandably, get furious when they feel wronged—especially by vague, hostile, or outright malicious reviews....

The commercial war has officially escalated, after JD enters the takeout business. In response to JD.com’s splashy entry into their duopolized takeout delivery game, Meituan—the undisputed heavyweight of that space—is fighting back in the only language consumers care about: massive coupons. My friend pulled 23.5RMB off a 20 meal? On average, a typical order runs around ¥48, so Meituan is basically slicing half off the bill just to keep people in its ecosystem....

I like to think about how to spend money well, with joy, efficiency, and ideally—being from Guangzhou which is literally the most delicious region in China, I take food seriously. Lately, there’s been an interesting bit of culinary gossip about the tech giants behind our takeout orders. I’ve written before about Meituan, the heavyweight in China’s food-delivery duopoly—a platform that has perfected the dark art of rent-seeking. It squeezes the life (and margin) out of both the restaurants and the couriers....

The art of internet archeology led me to the distinguished lecture given by Sendhil Mullainathan, “Economics in the Age of Algorithms”, at AEA Annual Meeting that took place in Hilton San Francisco Union Square—I’ve been there, several times! The talk took place Jan. 3, 2025. The video is available https://videosolutions.mediasite.com/Mediasite/Play/cb9d64c0274d4aae98b61dd6779791b31d I’ll write about it someday :)

What Is This Poster Even For? My advisor is letting me redesign the poster (the previous version isn’t that bad… isn’t it?) for our paper “Price Stability and Improved Buyer Utility with Presentation Design” (pdf) that’s going to be presented at The Web Conference. Fine. But, to be fair, he made a solid point. Yes, there are endless design guidelines and aesthetic choices—softwares (please, don’t use Powerpoint or Word…), color palettes, font choices, the use of white space (oh the cliche ’less is more’), clever placements of shapes and arrows to guide people’s eyeballs, etc etc etc....

I do have some (well, a little) Theoretical-CS background. I thought I was learning math for computer science in class—I took notes, solved problems, or may have even nodded sagely once or twice. But only after when I start reading the following books did I realize… ah, this is what they were trying to teach us. Whether you’re into algorithms, theory of computation, or occasionally need to find a quick recap or intermediate result to bypass some calculations yourself, the following are the textbooks that our professors quietly (or loudly) revere—slightly biased, but just to get started....

Ah, the sweet smell of competition: Freebies are flying on campus. Verified US students can snag two free months of ChatGPT Plus from March 31 to May 31, 2025 (chatgpt.com/students). And Google’s Gemini Advanced become freely available to US college students all the way through finals 2026 from April 17, 2025 (gemini.google/students/). Why Tech Giants Love Students (and Their Data)? Discounts to college students are the cheapest brand loyalty booster. By getting students accustomed to their ecosystem and tools (AI, cloud services, productivity apps), tech companies help shape the default workflows and preferences of the future workforce, creating built-in demand and fashion....

It’s a gift to have sharp music memories—the kind that catch a familiar vibe in something new. The two pieces below don’t share the same melody, but there’s something in the way the instruments blend, the vocals drift, the atmosphere builds. Hit play and feel the resemblance for yourself:

Scoring rules are really cool, and useful. This seminal survey paper has over 6k citations as of April 2025 :o Strictly proper scoring rules, prediction, and estimation tandfonline [pdf] Scoring rules assess the quality of probabilistic forecasts, by assigning a numerical score based on the predictive distribution and on the event or value that materializes. A scoring rule is proper if the forecaster maximizes the expected score for an observation drawn from the distribution F if he or she issues the probabilistic forecast F, rather than G ≠ F....

Didn’t know calculating expectation would take this long… Consider $n$ i.i.d. random variables $X_i$ drawn from Power Law distribution with support lowerbound $x_\text{min} = 1$ and the shape parameter $\alpha > 2$—in other words, the pdf of $X_i$ being $$ f_{X_i}(x) = (\alpha - 1) x^{-\alpha }, $$ and $$ F_{X_i}(x) =1 - x^{-(\alpha - 1)} \quad \text{ for }x \ge 1. $$ Btw, for the heavy-tailed distribution family, it can be more comfortable (and general) to understand random variable $X$ as $$ \Pr[X > x] \sim x^{-\alpha}....