genlib/sort: add bitonic, combinatorial sorter

complete with with api documentation and unittests

diff --git a/doc/api.rst b/doc/api.rst
index 958702da52777e2bd75d6a1a99a1359b9806e081..06c8a55334554b31afca983e07db7b0a1ccfda13 100644 (file)
--- a/doc/api.rst
+++ b/doc/api.rst
@@ -28,3 +28,10 @@ migen API Documentation
 .. automodule:: migen.genlib.cordic
         :members:
         :show-inheritance:
+
+:mod:`genlib.sort` Module
+------------------------------
+
+.. automodule:: migen.genlib.sort
+        :members:
+        :show-inheritance:

diff --git a/migen/genlib/sort.py b/migen/genlib/sort.py
new file mode 100644 (file)
index 0000000..1bc82ef
--- /dev/null
+++ b/migen/genlib/sort.py
@@ -0,0 +1,70 @@
+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])

diff --git a/migen/test/test_sort.py b/migen/test/test_sort.py
new file mode 100644 (file)
index 0000000..99785ab
--- /dev/null
+++ b/migen/test/test_sort.py
@@ -0,0 +1,28 @@
+import unittest
+from random import randrange
+
+from migen.fhdl.std import *
+from migen.genlib.sort import *
+
+from migen.test.support import SimCase, SimBench
+
+class BitonicCase(SimCase, unittest.TestCase):
+       class TestBench(SimBench):
+               def __init__(self):
+                       self.submodules.dut = BitonicSort(8, 4, ascending=True)
+
+       def test_sizes(self):
+               self.assertEqual(len(self.tb.dut.i), 8)
+               self.assertEqual(len(self.tb.dut.o), 8)
+               for i in range(8):
+                       self.assertEqual(flen(self.tb.dut.i[i]), 4)
+                       self.assertEqual(flen(self.tb.dut.o[i]), 4)
+
+       def test_sort(self):
+               def cb(tb, s):
+                       for i in tb.dut.i:
+                               s.wr(i, randrange(1<<flen(i)))
+                       i = [s.rd(i) for i in tb.dut.i]
+                       o = [s.rd(o) for o in tb.dut.o]
+                       self.assertEqual(sorted(i), o)
+               self.run_with(cb, 20)