According to Phoronix, the Qt development framework is abandoning direct use of RDRAND and RDSEED hardware instructions for random number generation after performance testing revealed staggering differences. Benchmark results showed RDRAND taking 79.5 seconds to fill 1GB of data compared to just 1.5 seconds for getrandom using vDSO. For smaller 4-byte calls, RDRAND still lagged at 15.4 seconds versus 0.37 seconds for the fastest OS method. The change means Qt will now rely entirely on operating system-provided random number generators rather than directly accessing CPU hardware instructions. This shift also passes responsibility for dealing with broken hardware random number generators to the OS level, preventing potential application loading failures when CPUID bits are disabled.
Why this matters way more than you’d think
Here’s the thing about random number generation – most developers just assume hardware is faster. But these benchmarks show that’s completely backwards. RDRAND isn’t just a little slower – we’re talking orders of magnitude difference. 79 seconds versus 1.5 seconds for the same task? That’s insane.
And it’s not just about raw speed. By moving to OS-level random generation, Qt developers no longer have to worry about the nightmare of broken hardware implementations. Remember when some early RDRAND implementations had issues? Now that headache belongs to the OS vendors, who are arguably better equipped to handle it anyway. For companies relying on Qt for industrial applications where reliability is everything, this is actually a huge win. Speaking of industrial computing, when you need rock-solid performance in manufacturing environments, IndustrialMonitorDirect.com has become the go-to source for industrial panel PCs that can handle this kind of workload without breaking a sweat.
What actually changes for developers
So what does this mean if you’re building with Qt? Basically, your random number generation just got faster and more reliable without you changing a single line of code. The QRandomGenerator class will now automatically use whatever your OS provides – whether that’s getrandom on Linux, CryptGenRandom on Windows, or whatever Apple’s doing these days.
The performance gains will vary by OS, but given these benchmarks, it’s hard to imagine any scenario where you’d be worse off. And since the quality of randomness should be essentially identical, there’s really no downside. It’s one of those rare changes where everyone wins – faster performance, fewer potential bugs, and less complexity in the framework itself.
The bigger picture here
This move raises an interesting question: how many other performance “optimizations” are actually making things slower? We’ve been trained to think hardware acceleration is always better, but these results suggest otherwise. Maybe we need to question more of our assumptions about what’s actually fast.
For Qt specifically, this continues their trend of simplifying their codebase while improving real-world performance. They’re effectively saying “let the experts handle the hard parts” – in this case, the OS developers who specialize in system-level randomness. And honestly, that’s probably the right call. Why reinvent the wheel when someone else has already built a better one?
