[Haskell-cafe] Fast Integer Input
Serguey Zefirov
sergueyz at gmail.com
Mon Aug 23 10:18:40 EDT 2010
2010/8/23 <200901104 at daiict.ac.in>:
> This function takes 1.8 seconds to
> convert 2000 integers of length 10^13000. I need it to be smaller that
> 0.5 sec. Is it possible?
2000 integers of magnitude 10^13000 equals to about 26 MBytes of data
(2000 numbers each 13000 digits long). Rounding 1.8 seconds to two
seconds we conclude that you proceed with speed about 13MBytes per
second. Assuming you have CPU clock frequency near 2.6GHz, you
performing about 200 clock cycles per input digit.
10^13000 roughly equal to 2^39000. Or (2^32)^1219 - 1219 32-bit words
of representation. So you're doing some last nextN =
(n*10)+currentDigit conversion operations in less that one clock cycle
per word.
Either I err'd in my math, or you're performing better than most of us
could expect. Maybe you are off in your 10^13000 by an order of
magnitude.
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