PRINEVILLE — Facebook’s third data center building, which is expected to be completed in December, will be the social media giant’s last in Central Oregon for the foreseeable future.

“We’re out of space to build in Prineville,” said Ken Patchett, director of Western data center operations, during a media tour of the facility Tuesday.

When the third building is finished, Facebook will have more than 1.1 million square feet of hardware under roof in Prineville. For the most part, the buildings house rack upon rack of servers, but Facebook revealed innovations that are geared toward a future that involves even more reliance on mobile applications and the use of artificial intelligence.

The company has placed its first mobile device testing lab in Prineville, which Facebook spokeswoman Lindsay Amos said is convenient for San Francisco Bay Area engineers who need to fly in to check on the operation. The testing lab will ensure that Facebook engineers don’t inadvertently cause performance or power problems for the all-important Facebook mobile app as they write software code changes, production engineer Antoine Reversat said.

Mobile advertising represented 82 percent of Facebook’s $5.2 billion in advertising revenue during the first quarter, according to the company, which also reported 1.51 billion monthly active mobile users around the world.

“We push code all the time, and we’ve got to do it right,” Patchett said.

The mobile lab also tests code changes for Facebook Messenger, Instagram and applications that Facebook uses in-house, Reversat said. In the lab, Facebook has nearly 2,000 smartphones hooked up to its network, and if a code change causes the app to scroll more slowly, or hogs battery life, the engineer will receive an email about the so-called “regression,” which must be fixed, he said.

Facebook is testing its code changes on phones as old as the iPhone 4s and Galaxy Nexus, released in 2011, Reversat said. The phones are kept inside insulated server cabinets, each with its own camera and Wi-Fi connection. Each cabinet holds 32 phones.

The mobile device testing lab resides in a fourth building, which Facebook calls “cold storage.” The cold storage servers essentially sleep most of the time because they house old photos, posts and other data that users do not access very often, Patchett said.

Facebook also showed off “Big Sur,” a next-generation server the company is using to power research on artificial intelligence. Facebook says Big Sur is unlike other supercomputers in that it doesn’t require special cooling systems. It’s integrated into the standard Facebook data center, which uses open-air cooling.

Facebook prides itself on efficiency, but its data centers are still enormous energy users. Facebook used 284 million kilowatt-hours of electricity in Prineville last year, according to the company’s annual sustainability report.

That’s the equivalent annual power use of about 26,000 U.S. homes, according to the U.S. Energy Information Administration. The Facebook data center campus does host a solar array that powers the lights and computers in its offices.

Patchett said that while Facebook’s electricity use is comparable to other data centers, the company is getting better-than-average computing power out of that energy, according to its internal metrics.

The third data center building will be 450,000 square feet, about 100,000 square feet larger than the first two, because it houses much more networking gear, Patchett said. That’s reflective of Facebook’s move to a disaggregated network, in which “everything is connected now to everything.”

Facebook employs about 165 people in Prineville.

— Reporter: 541-617-7860, kmclaughlin@bendbulletin.com