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

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Robert Jordens 2014-09-07 00:18:04 -06:00 committed by Sebastien Bourdeauducq
parent 11f58862db
commit 3d84a7a9de
3 changed files with 32 additions and 33 deletions
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23
examples/sim/cordic_err.py
View file

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

40
migen/genlib/cordic.py
View file

@ -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 * from migen.fhdl.std import *
@ -276,9 +276,12 @@ class TwoQuadrantCordic(Module):
a = [atanh(2**-i) for i in s] a = [atanh(2**-i) for i in s]
g = [sqrt(1 - 2**(-2*i)) for i in s] g = [sqrt(1 - 2**(-2*i)) for i in s]
zmax = sum(a)*2 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 # round here helps the width=2**i - 1 case but hurts the
# important width=2**i case # 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. gain = 1.
for gi in g: for gi in g:
gain *= gi gain *= gi
@ -316,30 +319,23 @@ class Cordic(TwoQuadrantCordic):
if self.func_mode != "circular": if self.func_mode != "circular":
return # no need to remap quadrants return # no need to remap quadrants
width = flen(self.xi)
widthz = flen(self.zi)
cxi, cyi, czi = self.xi, self.yi, self.zi cxi, cyi, czi = self.xi, self.yi, self.zi
self.xi = Signal((width, True)) self.xi = xi = Signal.like(cxi)
self.yi = Signal((width, True)) self.yi = yi = Signal.like(cyi)
self.zi = Signal((widthz, True)) self.zi = zi = Signal.like(czi)
### ###
pi2 = 1<<(widthz - 2) q = Signal()
if self.cordic_mode == "rotate": if self.cordic_mode == "rotate":
#rot = self.zi + pi2 < 0 self.comb += q.eq(zi[-2] ^ zi[-1])
rot = self.zi[-1] ^ self.zi[-2]
else: # vector else: # vector
rot = self.xi < 0 self.comb += q.eq(xi < 0)
#rot = self.xi[-1]
self.comb += [ self.comb += [
cxi.eq(self.xi), If(q,
cyi.eq(self.yi), Cat(cxi, cyi, czi).eq(Cat(-xi, -yi,
czi.eq(self.zi), zi + (1 << flen(zi) - 1)))
If(rot, ).Else(
cxi.eq(-self.xi), Cat(cxi, cyi, czi).eq(Cat(xi, yi, zi))
cyi.eq(-self.yi), )
czi.eq(self.zi + 2*pi2), ]
#czi.eq(self.zi ^ (2*pi2)),
),
]

2
migen/test/test_cordic.py
View file

@ -121,7 +121,7 @@ class CordicCase(SimCase, unittest.TestCase):
return xi, yi, 0 return xi, yi, 0
def proc(xi, yi, zi): def proc(xi, yi, zi):
return sqrt(xi**2 - yi**2), 0, atanh(yi/xi) 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): def test_vec_hyp(self):
self.setUp(cordic_mode="vector", func_mode="hyperbolic") self.setUp(cordic_mode="vector", func_mode="hyperbolic")