Inverse Symbolic Calculator

» see isc.carma.newcastle.edu.au as it lived, on the wayback machine

~ the eulogy ~

The Inverse Symbolic Calculator ran a search engine backwards. Ordinary mathematical software takes an expression and gives you a number. This took the number and tried to give you back the expression. You pasted in a truncated decimal, something like 0.5772156649, and it came back with candidate closed forms whose value sits near what you typed.

It opened on 18 July 1995 at the Centre for Experimental and Constructive Mathematics at Simon Fraser University in Burnaby, built by the Borwein brothers with Simon Plouffe. Underneath were two different machines doing the same job. The first was a lookup table holding fifty four million constants, which handles the case where your number is already famous and you just do not recognize it. The second was a set of integer relation algorithms, which handles the harder case by hunting for a combination of known constants that lands on your digits.

Plouffe took the idea further on his own account. His Inverter opened in 1998 with 214 million entries, and by 19 June 2010 the expanded tables held 3.702 billion of them. In 2016 he put out a portable version carrying three billion entries, which is a reasonable answer to the problem of depending on somebody else's web server.

In February 2010 the original changed hemispheres. CARMA, the Centre for Computer-Assisted Research Mathematics and its Applications at the University of Newcastle in Australia, took it over and ran it as ISC 2.0, also called ISC+. Jonathan Borwein had founded CARMA, so the service followed one of its authors from one hemisphere to another rather than being handed to strangers.

Borwein died on 2 August 2016. The calculator kept taking queries until early 2023, more than six years past the death of the man whose institute ran it, and for academic software that is a long unattended run.

~ the dossier ~

~ what the table was for ~

No job I have held has ever given me a reason to open this. The gap here is occupational rather than regional. The problem the ISC solved belongs to people doing pure mathematics, where a number falling out of an integral is a clue and the whole task is to prove what it equals. In engineering the number falling out of a computation is the deliverable, and you check it against a measurement rather than against a closed form.

What I can read, from the page the archive kept, is how plainly it was built. The last working version accepted either a floating point expression or correct Maple syntax, with a timeout bolted on for Maple input that took too long to evaluate, and a warning that factors of ten and decimal points were ignored so you had to rescale the results yourself. A tool that tells you up front which part of your input it is going to throw away is a tool written by the people who use it.

~ three hostnames, all dead ~

This thing outlived every address it ever had. The original path at cecm.sfu.ca was returning 404 by early 2007. Simon Fraser then kept the old CECM pages on a host called oldweb, which also died, and after that on one called wayback, which served the original ISC page as a static relic as late as 23 April 2024. Whoever updated Wikipedia's article in December 2024 recorded the status flatly: down as of the 28th. Today wayback.cecm.sfu.ca does not resolve at all, so even the archive copy is now unreachable.

The working version died earlier and more quietly. isc.carma.newcastle.edu.au served the full calculator page on 28 February 2023 and was returning 404 by 27 March 2023, so the service has a death window of under four weeks and no announcement anywhere inside it. The whole carma.newcastle.edu.au domain has since stopped resolving. What survives is carmamaths.org, a mirror of CARMA's materials, where the ISC page now holds a single sentence saying the calculator is down for maintenance indefinitely and pointing visitors at the original, whose host is also gone.

@}-->--

              )
             (_)
            .-'-.
            |   |
            |   |
            |   |
            |   |
          __|   |__   .-.
       .-'  |   |  `-:   :
      :     `---'     :-'
       `-._       _.-'
           '""""""

« previous  ·  random  ·  next »