[jeffbee]

There isn't any discussion of the cost at all. It just says the test run rate is down by 70%, it doesn't say anything about the defect detection rate, even though they say this is their cost function.

10 core-years per day sounds like a lot but it's only about a 10kW load, and they've saved 70% of that, or about $20 of opex per day.

[halbersa]

One of the authors here, I can't exactly deny that line was added to sound impressive, so guilty as charged. However the savings are much higher than $20/day for a few reasons:

* Many tasks run on expensive instances (hardware acceleration, Windows)

* We have OSX/Android pools that run on physical devices in a data centre (these are an order of magnitude more expensive than Linux)

* There are ancillary costs. For example each task generates artifacts which incur storage costs. These artifacts are downloaded which incur transfer costs.

* There are also overhead costs (idle time, rebooting, etc) that aren't counted in the 10 years / day stat.

All these things see a corresponding decrease in costs with fewer tasks.

[dmurray]

Is that really all? That would be 3650 cores running full time. 3W per core sounds too little for power consumption. And do power costs really dominate the price of running CPUs? I'm guessing the savings here are at least one order of magnitude more than your $20/day.

I get about $1000/day based on some EC2 prices for typical machines I've used, though I'm sure Mozilla's requirements are different and they can negotiate better prices than I can.

[jeffbee]

I probably missed a few factors, but I just hate a blog post that uses big-sounding numbers when they aren't big.

[bonoboTP]

Big for who? Hundreds of machines running constantly is big for me.