cordic: round() constants if not power of two bitwidth, cleanup, simplify some logic

diff --git a/examples/sim/cordic_err.py b/examples/sim/cordic_err.py
index bd22f2507a52e84b64d77460f1cb131128080366..d7b89b1cfc42cdc88c5cb786ec46a8af3e025e99 100644 (file)
--- a/examples/sim/cordic_err.py
+++ b/examples/sim/cordic_err.py
@@ -15,30 +15,30 @@ class TestBench(Module):
                        n = 1<<flen(self.cordic.xi)
                self.c = c = 2**(flen(self.cordic.xi) - 1)
                self.cz = cz = 2**(flen(self.cordic.zi) - 1)
+               x = int(xmax*c/self.cordic.gain)
                if i is None:
-                       i = [(int(xmax*c/self.cordic.gain), 0, int(cz*(i/n - .5)))
-                                       for i in range(n)]
+                       i = [(x, 0, int(cz*(2.*ii/n - 1))) for ii in range(n)]
                self.i = i
                random.shuffle(self.i)
                self.ii = iter(self.i)
                self.o = []
 
        def do_simulation(self, selfp):
+               if selfp.cordic.new_out:
+                       self.o.append((selfp.cordic.xo, selfp.cordic.yo, selfp.cordic.zo))
                if selfp.cordic.new_in:
                        try:
                                selfp.cordic.xi, selfp.cordic.yi, selfp.cordic.zi = next(self.ii)
                        except StopIteration:
                                raise StopSimulation
-               if selfp.cordic.new_out:
-                       self.o.append((selfp.cordic.xo, selfp.cordic.yo, selfp.cordic.zo))
 
        def run_io(self):
                run_simulation(self)
-               del self.i[-1], self.o[0]
+               del self.o[0]
                if self.i[0] != (0, 0, 0):
                        assert self.o[0] != (0, 0, 0)
-               if self.i[-1] != self.i[-2]:
-                       assert self.o[-1] != self.o[-2], self.o[-2:]
+               #if self.i[-1] != self.i[-2]:
+               #       assert self.o[-1] != self.o[-2], self.o[-2:]
 
 def rms_err(width, guard=None, stages=None, n=None):
        tb = TestBench(width=width, guard=guard, stages=stages,
@@ -87,9 +87,10 @@ def plot_function(**kwargs):
        xi, yi, zi = np.array(tb.i).T
        xo, yo, zo = np.array(tb.o).T
        fig, ax = plt.subplots()
+       #ax.plot(zi, xo-np.around(xi[0]*g*np.cos(zi/cz*np.pi)), "k-")
        ax.plot(zi, xo, "r,")
        ax.plot(zi, yo, "g,")
-       ax.plot(zi, zo, "g,")
+       ax.plot(zi, zo, "b,")
 
 
 if __name__ == "__main__":
@@ -101,6 +102,8 @@ if __name__ == "__main__":
        #plot_function(func_mode="hyperbolic", xmax=.3, width=16, n=333)
        #plot_function(func_mode="circular", width=16, n=333)
        #plot_function(func_mode="hyperbolic", cordic_mode="vector",
-    #        xmax=.3, width=16, n=333)
-       #plot_function(func_mode="circular", width=16, n=333)
+       #        xmax=.3, width=16, n=333)
+       plot_function(func_mode="circular",
+                       width=16, stages=15, guard=0,
+                       n=1000, xmax=.98)
        plt.show()

diff --git a/migen/genlib/cordic.py b/migen/genlib/cordic.py
index 0b9306657f7877a0e430cde83987a41cbfc6d33a..c6d134dd75fdb18a43733d6f9cee1b87985104be 100644 (file)
--- a/migen/genlib/cordic.py
+++ b/migen/genlib/cordic.py
@@ -1,4 +1,4 @@
-from math import atan, atanh, log, sqrt, pi, ceil
+from math import atan, atanh, log, sqrt, pi
 
 from migen.fhdl.std import *
 
@@ -276,9 +276,12 @@ class TwoQuadrantCordic(Module):
                        a = [atanh(2**-i) for i in s]
                        g = [sqrt(1 - 2**(-2*i)) for i in s]
                        zmax = sum(a)*2
-               a = [int(ai*2**(bits - 1)/zmax) for ai in a]
                # round here helps the width=2**i - 1 case but hurts the
                # important width=2**i case
+               cast = int
+               if log(bits)/log(2) % 1:
+                       cast = round
+               a = [cast(ai*2**(bits - 1)/zmax) for ai in a]
                gain = 1.
                for gi in g:
                        gain *= gi
@@ -316,30 +319,23 @@ class Cordic(TwoQuadrantCordic):
                if self.func_mode != "circular":
                        return # no need to remap quadrants
 
-               width = flen(self.xi)
-               widthz = flen(self.zi)
                cxi, cyi, czi = self.xi, self.yi, self.zi
-               self.xi = Signal((width, True))
-               self.yi = Signal((width, True))
-               self.zi = Signal((widthz, True))
+               self.xi = xi = Signal.like(cxi)
+               self.yi = yi = Signal.like(cyi)
+               self.zi = zi = Signal.like(czi)
 
                ###
 
-               pi2 = 1<<(widthz - 2)
+               q = Signal()
                if self.cordic_mode == "rotate":
-                       #rot = self.zi + pi2 < 0
-                       rot = self.zi[-1] ^ self.zi[-2]
+                       self.comb += q.eq(zi[-2] ^ zi[-1])
                else: # vector
-                       rot = self.xi < 0
-                       #rot = self.xi[-1]
+                       self.comb += q.eq(xi < 0)
                self.comb += [
-                               cxi.eq(self.xi),
-                               cyi.eq(self.yi),
-                               czi.eq(self.zi),
-                               If(rot,
-                                       cxi.eq(-self.xi),
-                                       cyi.eq(-self.yi),
-                                       czi.eq(self.zi + 2*pi2),
-                                       #czi.eq(self.zi ^ (2*pi2)),
-                               ),
-                               ]
+                               If(q,
+                                       Cat(cxi, cyi, czi).eq(Cat(-xi, -yi,
+                                               zi + (1 << flen(zi) - 1)))
+                               ).Else(
+                                       Cat(cxi, cyi, czi).eq(Cat(xi, yi, zi))
+                               )
+               ]

diff --git a/migen/test/test_cordic.py b/migen/test/test_cordic.py
index 7a715aae8679f719059b0d1fdd7043561c15232d..082ad13393cab79f1808e27d84981cc44ec49bce 100644 (file)
--- a/migen/test/test_cordic.py
+++ b/migen/test/test_cordic.py
@@ -121,7 +121,7 @@ class CordicCase(SimCase, unittest.TestCase):
                        return xi, yi, 0
                def proc(xi, yi, zi):
                        return sqrt(xi**2 - yi**2), 0, atanh(yi/xi)
-               self._run_io(50, gen, proc)
+               self._run_io(50, gen, proc, deltaz=2)
 
        def test_vec_hyp(self):
                self.setUp(cordic_mode="vector", func_mode="hyperbolic")