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cordic: round() constants if not power of two bitwidth, cleanup, simplify some logic
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parent
11f58862db
commit
3d84a7a9de
3 changed files with 32 additions and 33 deletions
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@ -15,30 +15,30 @@ class TestBench(Module):
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n = 1<<flen(self.cordic.xi)
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self.c = c = 2**(flen(self.cordic.xi) - 1)
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self.cz = cz = 2**(flen(self.cordic.zi) - 1)
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x = int(xmax*c/self.cordic.gain)
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if i is None:
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i = [(int(xmax*c/self.cordic.gain), 0, int(cz*(i/n - .5)))
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for i in range(n)]
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i = [(x, 0, int(cz*(2.*ii/n - 1))) for ii in range(n)]
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self.i = i
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random.shuffle(self.i)
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self.ii = iter(self.i)
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self.o = []
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def do_simulation(self, selfp):
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if selfp.cordic.new_out:
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self.o.append((selfp.cordic.xo, selfp.cordic.yo, selfp.cordic.zo))
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if selfp.cordic.new_in:
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try:
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selfp.cordic.xi, selfp.cordic.yi, selfp.cordic.zi = next(self.ii)
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except StopIteration:
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raise StopSimulation
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if selfp.cordic.new_out:
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self.o.append((selfp.cordic.xo, selfp.cordic.yo, selfp.cordic.zo))
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def run_io(self):
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run_simulation(self)
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del self.i[-1], self.o[0]
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del self.o[0]
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if self.i[0] != (0, 0, 0):
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assert self.o[0] != (0, 0, 0)
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if self.i[-1] != self.i[-2]:
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assert self.o[-1] != self.o[-2], self.o[-2:]
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#if self.i[-1] != self.i[-2]:
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# assert self.o[-1] != self.o[-2], self.o[-2:]
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def rms_err(width, guard=None, stages=None, n=None):
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tb = TestBench(width=width, guard=guard, stages=stages,
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@ -87,9 +87,10 @@ def plot_function(**kwargs):
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xi, yi, zi = np.array(tb.i).T
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xo, yo, zo = np.array(tb.o).T
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fig, ax = plt.subplots()
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#ax.plot(zi, xo-np.around(xi[0]*g*np.cos(zi/cz*np.pi)), "k-")
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ax.plot(zi, xo, "r,")
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ax.plot(zi, yo, "g,")
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ax.plot(zi, zo, "g,")
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ax.plot(zi, zo, "b,")
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if __name__ == "__main__":
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@ -102,5 +103,7 @@ if __name__ == "__main__":
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#plot_function(func_mode="circular", width=16, n=333)
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#plot_function(func_mode="hyperbolic", cordic_mode="vector",
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# xmax=.3, width=16, n=333)
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#plot_function(func_mode="circular", width=16, n=333)
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plot_function(func_mode="circular",
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width=16, stages=15, guard=0,
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n=1000, xmax=.98)
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plt.show()
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@ -1,4 +1,4 @@
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from math import atan, atanh, log, sqrt, pi, ceil
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from math import atan, atanh, log, sqrt, pi
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from migen.fhdl.std import *
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@ -276,9 +276,12 @@ class TwoQuadrantCordic(Module):
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a = [atanh(2**-i) for i in s]
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g = [sqrt(1 - 2**(-2*i)) for i in s]
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zmax = sum(a)*2
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a = [int(ai*2**(bits - 1)/zmax) for ai in a]
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# round here helps the width=2**i - 1 case but hurts the
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# important width=2**i case
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cast = int
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if log(bits)/log(2) % 1:
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cast = round
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a = [cast(ai*2**(bits - 1)/zmax) for ai in a]
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gain = 1.
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for gi in g:
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gain *= gi
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@ -316,30 +319,23 @@ class Cordic(TwoQuadrantCordic):
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if self.func_mode != "circular":
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return # no need to remap quadrants
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width = flen(self.xi)
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widthz = flen(self.zi)
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cxi, cyi, czi = self.xi, self.yi, self.zi
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self.xi = Signal((width, True))
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self.yi = Signal((width, True))
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self.zi = Signal((widthz, True))
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self.xi = xi = Signal.like(cxi)
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self.yi = yi = Signal.like(cyi)
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self.zi = zi = Signal.like(czi)
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###
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pi2 = 1<<(widthz - 2)
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q = Signal()
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if self.cordic_mode == "rotate":
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#rot = self.zi + pi2 < 0
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rot = self.zi[-1] ^ self.zi[-2]
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self.comb += q.eq(zi[-2] ^ zi[-1])
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else: # vector
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rot = self.xi < 0
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#rot = self.xi[-1]
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self.comb += q.eq(xi < 0)
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self.comb += [
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cxi.eq(self.xi),
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cyi.eq(self.yi),
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czi.eq(self.zi),
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If(rot,
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cxi.eq(-self.xi),
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cyi.eq(-self.yi),
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czi.eq(self.zi + 2*pi2),
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#czi.eq(self.zi ^ (2*pi2)),
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),
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If(q,
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Cat(cxi, cyi, czi).eq(Cat(-xi, -yi,
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zi + (1 << flen(zi) - 1)))
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).Else(
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Cat(cxi, cyi, czi).eq(Cat(xi, yi, zi))
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)
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]
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@ -121,7 +121,7 @@ class CordicCase(SimCase, unittest.TestCase):
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return xi, yi, 0
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def proc(xi, yi, zi):
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return sqrt(xi**2 - yi**2), 0, atanh(yi/xi)
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self._run_io(50, gen, proc)
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self._run_io(50, gen, proc, deltaz=2)
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def test_vec_hyp(self):
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self.setUp(cordic_mode="vector", func_mode="hyperbolic")
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