Podcast: When a Different OS Gets Different Results

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In this podcast, the Radio Free HPC team looks at problems in the scientific software world.

There’s a bug in Python scripts that caused different results in identical routines run on different operating systems. For example, the results on macOS Maverick and Windows 10 were significantly different than results from the same application run on Ubuntu 16 and macOS Mojave. As the guys discuss, it’s not a Python thing but a problem with the order in which files got read according to the operating system’s protocols. This impacts the sort order and thus the end results. The gang speculates on other causes of these types of problems and the fixes that should be employed.

Other Highlights:

  • Cyberstalking. Henry discusses how a stalker in Japan was trying to pin down the location of a female pop star. He used her selfies posted online to closely examine the reflection in her eyes, then using Google street view to find out where she lives.
  • Why AI is Dooming Us All. Dan introduces a new occasional feature, “Why AI is Dooming Us All.” According to Dan, AI is very brittle and can be fooled easily. He cites a case where just a few pieces of tape can make a stop sign look like a “Speed 45” sign to an AI.
  • Henry describes a great documentary about the history of computing in Minnesota, going in depth on the companies and technologies that originated in “The Star of the North” (Minnesota’s state motto. Their other state motto is, I think, “Minnesota: Gateway to the Dakotas”).
  • Shahin provides an update on Facebook’s plans for their shiny new Libra cryptocurrency, which is facing a bit of a bumpy ride. Several high-profile Libre partners have bailed out while Facebook stays the course. Interesting stuff.
  • Dan discusses a bug in the Linux Sudo command. Some miss-configured systems allow Sudo to have local/remote root access, thus making them superusers. He also manages to insult Phil Collins and his horrible Su-Su-Sudio song in the process. The guys discuss asking Linus Torvalds this question and Dan brings up how a person he knows once sold Linus a Christmas tree, which brings up a short discussion of what kind of tree Linus would purchase.

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  1. The problem isn’t Python. The problem isn’t the OS. The problem is that IEEE floating-point arithmetic lacks the associative property of addition, so the order of additions affects the answer. It shouldn’t. Posit arithmetic offers the ability to add real numbers without any rounding error until the sum is finally placed back into posit form, and I believe that eliminates the problem for these researchers and many others.