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Thursday, December 19, 2019

Modeling Chaotic Systems

The breadth of modeling capability is always important.  From a continuing investigation.


Numbers Limit How Accurately Digital Computers Model Chaos
UCL News

Researchers at University College London (UCL) in the U.K. and Tufts University found digital computers employ numbers that are based on flawed versions of actual numbers, which may lead to inaccuracies in simulations of chaotic systems and limit high-performance computing and machine learning applications. Digital computers only use rational numbers—which can be expressed as fractions—and these fractions' denominators must be a power of 2. The researchers used 4 billion single-precision floating-point numbers, ranging from plus to minus infinity, to compare the mathematical reality of a one-parameter chaotic system to digital systems' forecasts if all available single-precision floating-point numbers were utilized. The predictions were completely incorrect for certain values of the parameter, while calculations for others appeared correct, but deviated by up to 15%. Said UCL’s Peter Coveney, “Chaos is more commonplace than many people may realize and even for very simple chaotic systems, numbers used by digital computers can lead to errors that are not obvious but can have a big impact. Ultimately, computers can't simulate everything."... '

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