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Texas judge sends Uniloc packing in Rackspace patent suit

Turns out floating-point numbers aren't patentable

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In a rare move, the US District Court for the Eastern District of Texas has granted early dismissal of a patent lawsuit filed by Uniloc against Rackspace, having found that Uniloc's patent described nothing more than a mathematical formula and was therefore invalid.

"The early dismissal of this case delivers a clear message that patent assertion entities can't expect quick settlements on weak claims, a tactic many patent assertion entities use to monetize questionable patents," Rackspace general counsel Alan Schoenbaum said in a statement.

Rackspace was defended in the suit by Red Hat, which offers its customers indemnification against intellectual property claims under its Open Source Assurance program.

In this specific case, Uniloc had alleged that the way in which Linux handles floating-point arithmetic violated US Patent 5,892,697, Claim 1 of which purports to describe:

A method for processing floating-point numbers, each floating-point number having at least a sign portion, an exponent portion and a mantissa portion, comprising the steps of:
  • converting a floating-point number memory register representation to a floating-point register representation; 
  • rounding the converted floating-point number; 
  • performing an arithmetic computation upon said rounded number resulting in a new floating-point value; and
  • converting the resulting new floating-point register value to a floating-point memory register representation. 

Like many other operating systems, libraries, and applications, Linux's handling of floating-point numbers is based on the widely recognized IEEE Standard 754. But Uniloc had alleged that the specific implementation used by the open source OS infringed on its patent, which it claimed represented "a definite and substantive advancement to a concrete industry standard."

That advancement? Read the language for yourself. IEEE 754 specifies that you should carry out arithmetic operations on floating point numbers and then round them. Uniloc's patent describes a process where you round the numbers first and then do the arithmetic.

In documents filed with the court and obtained by Groklaw, Uniloc's lawyers argued (among other points) that its patent didn't merely describe a minor modification to a known algorithm – which would not be patentable – because no specific computation is mentioned.

"This step requires an arithmetic computation to be performed, but is not limited to any particular one. It could be multiplication, division, a logarithmic operation, etc. Likewise, the conversion steps do not require the application of any particular mathematical formula, let alone recite a mathematical formula," Uniloc's brief explains.

Chief Judge Leonard Davis wasn't buying it, however, and instead agreed with Rackspace and Red Hat that Uniloc's patent failed every legal test of validity – and that allowing it to stand would actually be harmful to society.

"Even when tied to computing, since floating-point numbers are a computerized numeric format, the conversion of floating-point numbers has applications across fields as diverse as science, math, communications, security, graphics, and games," Judge Davis wrote in his ruling. "Thus, a patent on Claim 1 would cover vast end uses, impeding the onward march of science."

A potentially historic ruling

Such a ruling is unusual for the Eastern District of Texas, which has long been notoriously plaintiff-friendly in patent cases. According to Rackspace's Schoenbaum, this was actually the first time that a patent complaint had ever been dismissed so quickly in the district.

It's certainly a place well familiar to Uniloc. A "non-producing entity" – patent troll, for short – Uniloc has 78 patent lawsuits pending in US courts as of this writing. All but five are in the Eastern District of Texas.

In a blog post on Thursday, Shoenbaum described Uniloc's case against Rackspace in no uncertain terms:

The patent at issue is a joke. Uniloc alleged that a floating point numerical calculation by the Linux operating system violated U.S. Patent 5,892,697 – an absurd assertion. This is the sort of low quality patent that never should have been granted in the first place and which patent trolls buy up by the bushel full, hoping for fast and cheap settlements.

Schoenbaum went on to note that patent litigation is now the top issue for Rackspace's legal team, and that the company's costs for defense against patent suits have increased 500 per cent since 2010 alone. As such, he praised Judge Davis's ruling:

It's refreshing to see that the judiciary recognizes that many of the fundamental operations of a computer are pure mathematics and are not patentable subject matter. We expect, and hope, that many more of these spurious software patent lawsuits are dismissed on similar grounds.

Uniloc did not immediately reply to The Register's requests for comment. ®

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