Ask Slashdot: How Reproducible Is Arithmetic In the Cloud?

goodminton writes "I'm research the long-term consistency and reproducibility of math results in the cloud and have questions about floating point calculations. For example, say I create a virtual OS instance on a cloud provider (doesn't matter which one) and install Mathematica to run a precise calculation. Mathematica generates the result based on the combination of software version, operating system, hypervisor, firmware and hardware that are running at that time. In the cloud, hardware, firmware and hypervisors are invisible to the users but could still impact the implementation/operation of floating point math. Say I archive the virutal instance and in 5 or 10 years I fire it up on another cloud provider and run the same calculation. What's the likelihood that the results would be the same? What can be done to adjust for this? Currently, I know people who 'archive' hardware just for the purpose of ensuring reproducibility and I'm wondering how this tranlates to the world of cloud and virtualization across multiple hardware types."

Comments

bend reality

[goombah99]

The result is always the same, but the definition of reality is changing. The result of every single calculation is in fact 42 in some units. The hard part is figuring out the units.

Easiest solution

[ShaunC]

Just scroll down a couple of posts. "Quite soon the Wolfram Language is going to start showing up in lots of places, notably on the web and in the cloud."

Problem solved!

Obligatory Comic

[ttucker]

http://www.smbc-comics.com/?id=2999

Re:Arbitray precision

[weilawei]

So I'm supposed to do all my calculations without any Pi? How can you have any Pi if you don't eat your machine?

Re:Fixed-point arithmetic

[NEDHead]

I have a mechanical calculator that is extremely reliable, so long as you oil it.

Re:Numerical instability

[brantondaveperson]

This is the only answer so far that makes sense, which is a pity because

A) It's an AC
and
B) The point is moot, not mute.

But we all knew that, didn't we.

Re:Fixed-point arithmetic

[fuzzyfuzzyfungus]

Or simply don't use the broken "cloud computing" model. If you have some calculations to do, and care the least about the results, how about buying a computer that does those calculations for you?

In other news, many problems become much easier when you assume a suitably large pile of money.

Incidentally, the same is true of explosives, amphetamines, and hookers.

Re:Fixed-point arithmetic

[fuzzyfuzzyfungus]

"How do I test for Turing completeness "on the cloud"?"

This one is actually a nontrivial challenge. Once the tape starts to get damp, you need to keep track of the probability that executing a given head-moving operation will cause the tape to snap and abruptly leave you with a confused finite state machine...

Re:Fixed-point arithmetic

[philip.paradis]

Incidentally, the same is true of explosives, amphetamines, and hookers.

I don't have to be a mathematician to say that sounds like one hell of a party.

Re:Fixed-point arithmetic

[noh8rz10]

that link has a lot of words.