On 2012/05/11 20:49 , Joey K Tuttle wrote: > Thanks for the reminders - your Hilbert one gives me the first chance to > report a crash of J on the iPad. > > I tried it on my iMac > > H=: %@>:@(+/~)@i. > 6!:2 '%. H 100x' > 80.0178 > > and then on the iPad - but after a few minutes, the app crashed, hard to > say what happened, not likely a memory issue since it takes considerably > less space than 500 500 ?@$ 1000
Notes about something I only vaguely understand can lead to an interesting discovery process. This one was no exception. First, I hadn't read about extended percision and rational numbers being available until I began investigating what the trailing x meant. Having played with extened percision a little in .Net, I was curious if the size of the computation would indeed be smaller. It runs too slow on my tablet, but on my Windows machine I found 7!:2 '%. H 100x' 22949760 is about thirty percent larger than 7!:2 '%. 500 500 ?@$ 1000' 17305088 As I looked at the two approaches, I began noticing how fast their answers divirged. While the ratio is excellent at H 4, it is terrible by H9. I've done enough testing now to know this is NOT just the Android port. Both 32 and 64 bit Windows have the same issue. The following output was created with J64 Windows j64-701a_setup.exe 0j2":(%.H 9)% %.H 9x 9.21 4.19 1.64 1.00 0.98 1.01 1.00 0.99 1.10 15.23 5.15 1.75 1.00 0.98 1.01 1.00 0.99 1.10 19.85 5.88 1.82 1.00 0.98 1.01 1.00 0.99 1.09 23.51 6.47 1.88 1.00 0.98 1.01 1.00 0.99 1.09 26.48 6.94 1.93 1.01 0.98 1.01 1.00 0.99 1.09 28.93 7.33 1.98 1.01 0.98 1.01 1.00 0.99 1.09 31.01 7.66 2.01 1.01 0.98 1.01 1.00 0.99 1.09 32.77 7.94 2.04 1.01 0.97 1.01 1.00 0.99 1.09 34.30 8.19 2.07 1.01 0.97 1.01 1.00 0.99 1.09 Having compared the results with other platforms, I can confirm it is the floating version that is wrong. -- Paul ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
