We introduce the bilinear bandit problem with low-rank structure where an action is a pair of arms from two different entity types, and the reward is a bilinear function of the known feature vectors of the arms. The problem is motivated by numerous applications in which the learner must recommend two different entity types as one action, such as a male / female pair in an online dating service. The unknown in the problem is a $d_1$ by $d_2$ matrix $\mathbf{\Theta}^*$ with rank $r \ll \min\{d_1,d_2\}$ governing the reward generation. Determination of $\mathbf{\Theta}^*$ with low-rank structure poses a significant challenge in finding the right exploration-exploitation tradeoff. In this work, we propose a new two-stage algorithm called "Explore-Subspace-Then-Refine" (ESTR). The first stage is an explicit subspace exploration, while the second stage is a linear bandit algorithm called "almost-low-dimensional OFUL" (LowOFUL) that exploits and further refines the estimated subspace via a regularization technique. We show that the regret of ESTR is $\tilde{O}((d_1+d_2)^{3/2} \sqrt{r T})$ (where $\tilde{O}$ hides logarithmic factors), which improves upon the regret of $\tilde{O}(d_1d_2\sqrt{T})$ of a naive linear bandit reduction. We conjecture that the regret bound of ESTR is unimprovable up to polylogarithmic factors.

Incorporating digital assistants into modern vehicles has proven transformative for drivers, but only the folks who can afford to pony up for a new(ish) car that has them built in. For those of us still driving older models, those features aren't readily available unless we pull out our phones while driving -- not good. But with the new Link Drive from JBL, any vehicle with a cigarette lighter can offer Google Assistant's help to its passengers. After plugging in the device and pairing it with either an Apple or Android smartphone, activating it is as simple as saying "hey Google." You'll also need to pair it with your stereo, though it can also be connected through the system's aux port.

It was only a matter of time, really. Instant Brands has announced that its Instant Pot Smart WiFi pressure cooker now supports Google Assistant, making it possible to start cooking or check on the status without pulling out your phone or peeking at the tiny display. It's the height of culinary luxury, but it could be incredibly helpful if you'd rather not drop what you're doing to start your rice or check on your brisket. The cooker officially sells for $150 with a 6-quart capacity. You probably won't go out of your way to get an Instant Pot for Google Assistant support, but it could make the ultra-trendy device feel more at home with the rest of your connected kitchen devices.

LG has revealed a consumer version of its roll-up TV set at the CES trade show in Las Vegas. The Signature OLED TV R is built on a concept unveiled last year, in which the screen retracts into a base when not in use so it is less obtrusive. LG plans to sell the device in the US before the end of 2019, but has yet to reveal the month or price. Experts say the technology is unlikely to become a mass-market proposition for many years to come. "It's a 4K set rather than 8K, so you could argue there's a compromise there - but otherwise this is a very high-end design that is going to be very costly," commented Jack Wetherill from the consultancy Futuresource.

Arlo is already known for its 4K security camera and doorbell, but for CES 2019, the company has launched a complete security system. The key component is a new multi-purpose sensor that can detect window and door breaches, motion, smoke, carbon monoxide, water leaks and more. The other pieces are a siren, remote control and hub that works with Arlo's various cameras, along with Zigbee and Z-Wave devices. HomeKit will be supported by Arlo's Ultra 4K HDR Wire-Free and Arlo Pro 2 security cameras systems via a firmware update in Q1 2019. It'll let iPhone and iPad users access the cameras using the Apple Home app or Siri commands.

Ring's latest video doorbell attaches to the peephole on a front door, making it suitable for renters or apartment residents who often cannot drill into the wall next to the door. Announced at CES, the Ring Door View Cam delivers live high-definition video with the same features as Ring's other doorbells. The battery-operated unit comes in two parts. The outside half is styled along the same lines as Ring's Video Doorbell Pro, although instead of one lens, there are two: The top one is the conventional peephole door viewer, so the old analog function is retained, and the one beneath it is the video camera. The indoor half has the viewing lens for the conventional peephole and is where the battery is installed.

At the Consumers Electronics Show on Monday, the South Korean tech giant took the wraps off the Signature Series OLED TV R, its first-ever OLED television with a screen that can roll itself up and is also voice-activated. After the prototype was teased in 2018, LG announced today that the rollable TV will finally hit the shelves this year, with a launch date expected sometime in the spring. LG didn't disclose pricing details about the rollable TV. The OLED TV R is designed to be in the room when you want it and disappear when you don't, with three different modes that let users decide the size of the screen. 'LG's rollable OLED TV is a true game-changer, freeing users from the limitations of the wall and allowing them to curate their own personal space,' the company explained. Users can choose from three modes - full view, line view and and zero view.

No matter the language, the principles are still the same--customers should be the focus of every company. South American companies face the volatile world of instability and inflation, but they still show that focusing on customers can lead to success. Here are 10 of the most customer-focused companies in South America. Arcos Dorados is based in Brazil and is the world's largest independent McDonald's franchisee with stores in more than 20 Latin American countries. The brand focuses on "cooltura de servicio", or "service culture," and encourages each employee to provide personalized service to customers.

Even without a booth, Apple is looming large over CES. In a giant billboard that went up on the side of the Springhill Suites Marriott hotel near the Vegas strip late last week, Apple is touting the privacy features baked into the iPhone, telling people, "What happens on your iPhone, stays on your iPhone." It's a clever and effective ad that plays off the classic Vegas slogan. In an age of regular data breaches and scary hacks, privacy and security have become a really big deal. Apple has made privacy a major component of its iPhone sales pitch for years, so while the ad might not mention Google, Samsung, or Amazon, it's clearly aimed at trolling Apple's biggest rivals and their somewhat laissez-faire approach to privacy.

I recently attended a holiday potluck hosted by a tech-junkie friend who had decked out his one-bedroom apartment with smart speakers, smart lights, and small, infrared motion sensors that looked disconcertingly like cameras. Towards the end of the party, after one of the guests disappeared into the back of the apartment, another decided to play a prank. "Hey Google, turn off bathroom lights," he said quietly into a nearby sensor. A few seconds later we heard an exaggerated shriek. "Hey Google, turn lights red," my friend joined in, grinning.