Hello, > 2. For the purposes of reserving memory in block sizes that can be > easily reallocated, I like to use powers of two. So if I have, e.g., a > dynamic array, I might start with a size of 1024 and then double it > when it hits capacity. Hopefully this smoothes memory management, as I > am using a lot of memory... > > Anyway, what I'd like is a simple function that can quickly identify the > next power-of-two larger than an arbitrary number. So if I feed the > function 472, it will return 512. Thus far I haven't been able to > figure out how to do this without a big if-then-else nest. Is there > some clever way to request that the processor return the position of > the leftmost '1' in 00101101?
Solutions with loops have already been posted, here one without any for completeness: function next_power_of_2(v : dword) : dword; begin // make sure that x <= 2^31 and x <> 0 dec(v); v := v or (v >> 1); v := v or (v >> 2); v := v or (v >> 4); v := v or (v >> 8); v := v or (v >> 16); inc(v); result := v; end; Explanation: http://bits.stephan-brumme.com/roundUpToNextPowerOfTwo.html Hth, Thomas -- Jetzt kostenlos herunterladen: Internet Explorer 8 und Mozilla Firefox 3.5 - sicherer, schneller und einfacher! http://portal.gmx.net/de/go/chbrowser _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
