coefficients: cleanup and refactor some code into CoefficientSource

artiq/wavesynth/coefficients.py

@@ -46,7 +46,7 @@ class UnivariateMultiSparseSpline(UnivariateMultiSpline):
 
 def pad_const(x, n, axis=0):
     """Prefix and postfix the array `x` by `n` repetitions of the first and
-    last vlaue along `axis`.
+    last value along `axis`.
     """
     a = np.repeat(x.take([0], axis), n, axis)
     b = np.repeat(x.take([-1], axis), n, axis)
@@ -86,9 +86,9 @@ class CoefficientSource:
     def crop_x(self, start, stop, num=2):
         """Return an array of valid sample positions.
 
-        This function needs to be implemented only if this
+        This method needs to be overloaded if this `CoefficientSource`
-        `CoefficientSource` does not support sampling at arbitrary
+        does not support sampling at arbitrary positions or at arbitrary
-        positions.
+        density.
 
         :param start: First sample position.
         :param stop: Last sample position.
@@ -99,15 +99,23 @@ class CoefficientSource:
         return np.linspace(start, stop, num)
 
     def scale_x(self, x, scale):
+        # TODO: This could be moved to the the Driver/Mediator code as it is
+        # device-specific.
         """Scale and round sample positions.
 
+        The sample times may need to be changed and/or decimated if
+        incompatible with hardware requirements.
+
         :param x: Input sample positions in data space.
         :param scale: Data space position to cycles conversion scale,
             in units of x-units per clock cycle.
         :return: `x_sample`, the rounded sample positions and `durations`, the
             integer durations of the individual samples in cycles.
         """
-        raise NotImplementedError
+        t = np.rint(x/scale)
+        x_sample = t*scale
+        durations = np.diff(t).astype(np.int)
+        return x_sample, durations
 
     def __call__(self, x, **kwargs):
         """Perform sampling and return coefficients.
@@ -118,25 +126,18 @@ class CoefficientSource:
         raise NotImplementedError
 
     def get_segment_data(self, start, stop, scale, cutoff=1e-12,
-                         min_duration=1, min_length=20,
                          target="bias", variable="amplitude"):
         """Build wavesynth segment data.
 
         :param start: see `crop_x()`.
         :param stop: see `crop_x()`.
         :param scale: see `scale_x()`.
-        :param num: see `crop_x()`.
         :param cutoff: coefficient cutoff towards zero to compress data.
-        :param min_duration: Minimum duration of a line.
-        :param min_length: Minimum segment length to space triggers.
         """
         x = self.crop_x(start, stop)
         x_sample, durations = self.scale_x(x, scale)
         coefficients = self(x_sample)
-        np.clip(np.fabs(durations), min_duration, None, out=durations)
+        if len(x_sample) == 1 and start == stop:
-        if len(durations) == 1:
-            durations[0] = max(durations[0], min_length)
-        if start == stop:
             coefficients = coefficients[:1]
         # rescale coefficients accordingly
         coefficients *= (scale*np.sign(durations))**np.arange(
@@ -146,12 +147,14 @@ class CoefficientSource:
         return build_segment(durations, coefficients, target=target,
                              variable=variable)
 
-    def extend_segment(self, segment, *args, **kwargs):
+    def extend_segment(self, segment, trigger=True, *args, **kwargs):
         """Extend a wavesynth segment.
 
         See `get_segment()` for arguments.
         """
-        for line in self.get_segment_data(*args, **kwargs):
+        for i, line in enumerate(self.get_segment_data(*args, **kwargs)):
+            if i == 0:
+                line["trigger"] = True
             segment.add_line(**line)
 
 
@@ -183,36 +186,42 @@ class SplineSource(CoefficientSource):
             x = self.x[ia:ib]
         return np.r_[start, x, stop]
 
-    def scale_x(self, x, scale, nudge=1e-9):
+    def scale_x(self, x, scale, min_duration=1, min_length=20):
+        """
+        Due to minimum duration and/or minimum segment length constraints
+        this method may drop samples from `x_sample` or adjust `durations` to
+        comply. But `x_sample` and `durations` should be kept consistent.
+
+        :param min_duration: Minimum duration of a line.
+        :param min_length: Minimum segment length to space triggers.
+        """
         # We want to only sample a spline at t_knot + epsilon
         # where the highest order derivative has just jumped
         # and is valid at least up to the next knot after t_knot.
         #
-        # To ensure that we are on the right side of a knot:
+        # To ensure that we are on the correct side of a knot:
         # * only ever increase t when rounding (for increasing t)
         # * or only ever decrease it (for decreasing t)
-        #
+        t = x/scale
-        # The highest derivative is discontinuous at t
+        inc = np.diff(t) >= 0
-        # and the correct value for a segment is obtained
-        # for t_int >= t_float == t_knot (and v.v. for t decreasing).
-        x = x/scale
-        inc = np.diff(x) >= 0
         inc = np.r_[inc, inc[-1]]
-        x = np.where(inc, np.ceil(x + nudge), np.floor(x - nudge))
+        t = np.where(inc, np.ceil(t), np.floor(t))
-        if len(x) > 1 and x[0] == x[1]:
+        dt = np.diff(t.astype(np.int))
-            x = x[1:]
+
-        if len(x) > 1 and x[-2] == x[-1]:
+        valid = np.absolute(dt) >= min_duration
-            x = x[:-1]
+        dt = dt[valid]
-        x_sample = x[:-1]*scale
+        t = t[np.r_[True, valid]]
-        durations = np.diff(x.astype(np.int))
+        if dt.shape[0] == 1:
-        return x_sample, durations
+            dt[0] = max(dt[0], min_length)
+        x_sample = t[:-1]*scale
+        return x_sample, dt
 
     def __call__(self, x):
         return self.spline(x)
 
 
 class ComposingSplineSource(SplineSource):
-    # TODO
+    # TODO: verify, test, document
     def __init__(self, x, y, components, order=4, pad_dx=1.):
         self.x = np.asanyarray(x)
         assert self.x.ndim == 1
@@ -236,18 +245,18 @@ class ComposingSplineSource(SplineSource):
             components, self.x, order)
 
     def __call__(self, t, gain={}, offset={}):
-        der = list((set(self.components.n) | set(offset)) & set(self.der))
+        der = list((set(self.components.n) | set(offset))
+                   & set(range(len(self.splines))))
         u = np.zeros((self.splines[0].order, len(self.splines[0].s), len(t)))
         # der, order, ele, t
         p = np.array([self.splines[i](t) for i in der])
-        # order, der, None, t
-        s = self.components(t)
         s_gain = np.array([gain.get(_, 1.) for _ in self.components.n])
-        s = s[:, :, None, :]*s_gain[None, :, None, None]
+        # order, der, None, t
+        s = self.components(t)[:, :, None, :]*s_gain[None, :, None, None]
         for k, v in offset.items():
-            if v and k in self.der:
+            if v:
-                u += v*p[self.der.index(k)]
+                u += v*p[k]
-        ps = p[[self.der.index(_) for _ in self.shims.der]]
+        ps = p[self.shims.n]
         for i in range(u.shape[1]):
             for j in range(i + 1):
                 u[i] += binom(i, j)*(s[j]*ps[:, i - j]).sum(0)