R-alpha: .Machine and external programs

George White (gwhite@cabot.bio.dfo.ca)
Mon, 18 Nov 96 12:17:43 AST

Message-Id: <199611181619.RAA21028@hypatia.math.ethz.ch>
From: George White <gwhite@cabot.bio.dfo.ca>
Subject: R-alpha: .Machine and external programs
To: r-testers@stat.math.ethz.ch
Date: Mon, 18 Nov 96 12:17:43 AST

In view of the potential for different f.p. behavior for R and for 
external programs, it might be useful to include the machar routine 
both internally for .Machine and in a form that can be used 
externally.  In general, the external version might die if 
signalling is set, or might return a different underflow or rounding mode.  

Most systems I have used provide some calls to modify the f.p. 
hardware registers, but they are usually not easy to find and use.
Also, given an object file, I don't know if there is any way to 
determine what f.p. settings the file makes, so there is still a
potential for problems.  About all you can do to help users is 
provide a few simple tools to help them look into the issue without
resorting to a debugger.

  George N. White III                | Internet: <aa056@chebucto.ns.ca>
  Department of Fisheries and Oceans | DFO email: GWhite@BIOnet.BIO.DFO.ca
  Ocean Sciences Division            | Time Zone: Atlantic (AST4ADT)
  Bedford Institute of Oceanography  | phone: (08:00-16:00)
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