OkCupid users refine their interests by answering up to 3 000 questions.

Washington - Kate Chan, a 30-year-old digital marketer in Silicon Valley, first approached dating apps with a blend of curiosity and hope that they'd help her find a great guy.

But after six months of dead-end mismatches with guys she thought were boring or work-obsessed, she has gone back to what she called "meeting the old-fashioned way": without a screen. She now meets guys at do-it-yourself crafting meet-ups and her rock-climbing gym.

"I didn't want to rely on the algorithms anymore," she said. "When it comes down to it, I really have to see that person face to face, to get that intuition, that you don't get in a digital way."

But when it comes to the algorithms of love, many say they are losing faith. They wonder whether the valley - a place infamously inhospitable to romance and with the most lopsided gender imbalance in the country - has proven too vexing for even its own dating apps. But they're also left with a more fundamental doubt: Maybe the human mysteries of chemistry and attraction aren't problems big data can solve.

Melissa Hobley, an executive at the dating app OkCupid, hears the complaints about the apps regularly and thinks they get a bad rap. Finding love, she added, takes commitment and energy - and, yes, time, no matter how inefficiently it's spent.

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OkCupid users refine their interests by answering up to 3 000 questions, including "Should a country always need the UN's approval before declaring war?"

Many of the most popular have the feel of a slot machine, including Tinder (swipe right on someone you like, and you chat if there's a match); Bumble (swiping, but only women can initiate) and Coffee Meets Bagel (swiping, but with only a handful of matches a day).