On 08/11/06, Tim Hochberg <tim.hochberg@ieee.org> wrote:
It has always been my experience (on various flavors or Pentium) that operating on NANs is extremely slow. Does anyone know on what hardware NANs are *not* slow? Of course it's always possible I just never notice NANs on hardware where they aren't slow.
On an opteron machine I have access to, they appear to be no slower (and even faster for some transcendental functions) than ordinary floats: In [13]: a=zeros(1000000) In [14]: %time for i in xrange(1000): a += 1.1 CPU times: user 6.87 s, sys: 0.00 s, total: 6.87 s Wall time: 6.87 In [15]: a *= NaN In [16]: %time for i in xrange(1000): a += 1.1 CPU times: user 6.86 s, sys: 0.00 s, total: 6.86 s Wall time: 6.87 On my Pentium M, they are indeed significantly slower (three times? I didn't really do enough testing to say how much). I am actually rather offended by this unfair discrimination against a citizen in good standing of the IEEE floating point community. A. M. Archibald ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642