litex/migen/genlib/sort.py

71 lines
1.8 KiB
Python

from migen.fhdl.std import *
from migen.fhdl import verilog
class BitonicSort(Module):
"""Combinatorial sorting network
The Bitonic sort is implemented as a combinatorial sort using
comparators and multiplexers. Its asymptotic complexity (in terms of
number of comparators/muxes) is O(n log(n)**2), like mergesort or
shellsort.
http://www.dps.uibk.ac.at/~cosenza/teaching/gpu/sort-batcher.pdf
http://www.inf.fh-flensburg.de/lang/algorithmen/sortieren/bitonic/bitonicen.htm
http://www.myhdl.org/doku.php/cookbook:bitonic
Parameters
----------
n : int
Number of inputs and output signals.
m : int
Bit width of inputs and outputs. Or a tuple of `(m, signed)`.
ascending : bool
Sort direction. `True` if input is to be sorted ascending,
`False` for descending. Defaults to ascending.
Attributes
----------
i : list of Signals, in
Input values, each `m` wide.
o : list of Signals, out
Output values, sorted, each `m` bits wide.
"""
def __init__(self, n, m, ascending=True):
self.i = [Signal(m) for i in range(n)]
self.o = [Signal(m) for i in range(n)]
self._sort(self.i, self.o, int(ascending), m)
def _sort_two(self, i0, i1, o0, o1, dir):
self.comb += [
o0.eq(i0),
o1.eq(i1),
If(dir == (i0 > i1),
o0.eq(i1),
o1.eq(i0),
)]
def _merge(self, i, o, dir, m):
n = len(i)
k = n//2
if n > 1:
t = [Signal(m) for j in range(n)]
for j in range(k):
self._sort_two(i[j], i[j + k], t[j], t[j + k], dir)
self._merge(t[:k], o[:k], dir, m)
self._merge(t[k:], o[k:], dir, m)
else:
self.comb += o[0].eq(i[0])
def _sort(self, i, o, dir, m):
n = len(i)
k = n//2
if n > 1:
t = [Signal(m) for j in range(n)]
self._sort(i[:k], t[:k], 1, m) # ascending
self._sort(i[k:], t[k:], 0, m) # descending
self._merge(t, o, dir, m)
else:
self.comb += o[0].eq(i[0])