Re: [AMBER] Amber 20 on AMD ryzen + Nvidia 30XX

From: Jason Swails <>
Date: Thu, 19 Nov 2020 19:34:20 -0500

On Wed, Nov 11, 2020 at 8:47 AM Jordi Bujons <>

> "On AMD Ryzen 3000 series CPUs, the hardware random number generator
> (RDRAND) can behave incorrectly, always returning -1 (0xFFFFFFFF). When
> this
> hardware bug is detected at runtime, GROMACS will switch to its
> software-based pseudo-random number generator instead."
> I wonder if this might also affect AMBER, or if AMD has already solved this
> bug and it is not a problem now. Do you know anything about this?

Amber uses a software-based PRNG seeded, by default, from the system
clock. Hardware RNGs that draw from system entropy are great for
cryptographic applications where true randomness is an essential ingredient
for cybersecurity, but the Amber approach has proven sufficient for
generating distinct streams for separate simulations over years of use even
in situations with batch job submission. Even though there are possibly
common scenarios that would result in replicate random streams, in practice
I've never seen it happen.

All the best,

Jason M. Swails
AMBER mailing list
Received on Thu Nov 19 2020 - 17:00:02 PST
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