Installing R on RedHat7.0
On Fri, 3 Nov 2000, Prof Brian D Ripley wrote:
On Fri, 3 Nov 2000, Tom Wainwright wrote:
Thanks! Building from source worked, and the demos all run. Several others report that R runs smoothly on RedHat7. However, not all the tests in $R_HOME/tests succeed. When I do "make test-Examples" in that directory, it fails executing "base-Ex.R" in the "eigen" section, with the error: Error: abs(sm %*% V - V %*% diag(lam)) < 60 * Meps is not TRUE This appears to be a numerical precision problem. Checking, Meps (i.e. .Machine.double.eps) is 1.084202e-19. Is this a reasonable value for a Pentium III?
No. .Machine$double.eps should be about 2e-16. An i686 does not have 19 digits of precision. Here's what gcc-2.95.2 gives on a PIII under RH6.2:
<snip>
The likely story is that that beta compiler is even farther from IEEE-compliant than is usual for gcc on Linux. Some of us are too nervous about it to even try an installation.
As the value is 2^-63 it may be that the machine precision calculation is being done entirely internally to the chip, using the 80-bit extended double format, which has this level of precision. This is certainly wrong and new; I don't know enough about the machine precision calculations to know if it is really a compiler bug or whether it is something the compiler was previously allowed to do but didn't. -thomas Thomas Lumley Assistant Professor, Biostatistics University of Washington, Seattle -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._