3 ms·

That's right, any iterative solver method (which already encompasses most of the low level numerical solvers used in physics today) or, more generally, any meth

That's right, any iterative solver method (which already encompasses most of the low level numerical solvers used in physics today) or, more generally, any method that algorithmically guarantees satisfying a particular mathematical constraint after each timestep (say, if you're enforcing fluid incompressibility at each timestep, most* single bitflips will not cause errors that would accumulate over time), etc. [*] There are exceptions in specific circumstances most of which would produce obviously wrong results or crash the simulation outright. However, I'm not claiming that single bitflips are never an issue for simulations, only that it happens much less often than people sometimes think.

sillysaurus3 9y ago
If a one-bit error causes the sign bit to flip, your position can go from 129,121.34 to -129,121.34. Obviously this is rare, but it seems mistaken to say that the simulation's parameters can prevent errors arising from this. Also, it's not just physics simulations that are at risk. Voxel renderings are especially susceptible to one-bit errors.
- keldaris 9y ago
  Not sure exactly what simulation you're referring to with the position example, in most of my code that would either be fixed in the next timestep or make the whole thing blow up immediately. Anyway, I haven't argued against using ECC memory in any of these comments. I've argued that you should know your needs and choose accordingly, and that ECC memory isn't free and therefore cannot be a universally optimal default for everyone. For much of my physics work I've found ECC memory not to be worth the cost at all. For other things, like most database servers (and perhaps voxel rendering, I don't have enough experience there to comment) ECC memory is clearly worth it. I just think people should invest some thought into the question before evangelizing for or against ECC in the general case.

sillysaurus3 9y ago

If a one-bit error causes the sign bit to flip, your position can go from 129,121.34 to -129,121.34. Obviously this is rare, but it seems mistaken to say that the simulation's parameters can prevent errors arising from this. Also, it's not just physics simulations that are at risk. Voxel renderings are especially susceptible to one-bit errors.

keldaris 9y ago
Not sure exactly what simulation you're referring to with the position example, in most of my code that would either be fixed in the next timestep or make the whole thing blow up immediately. Anyway, I haven't argued against using ECC memory in any of these comments. I've argued that you should know your needs and choose accordingly, and that ECC memory isn't free and therefore cannot be a universally optimal default for everyone. For much of my physics work I've found ECC memory not to be worth the cost at all. For other things, like most database servers (and perhaps voxel rendering, I don't have enough experience there to comment) ECC memory is clearly worth it. I just think people should invest some thought into the question before evangelizing for or against ECC in the general case.