Improve handling of h_center parameter in linop.CircularConvolve (#…

…299)

* Support broader range of h_center values

* Add tests for h_center parameter

scico/linop/_circconv.py

@@ -10,12 +10,14 @@
 import math
 import operator
 from functools import partial
-from typing import Optional, Tuple
+from typing import Optional, Sequence, Tuple, Union
 
 import numpy as np
 
 from jax.dtypes import result_type
 
+from jaxlib.xla_extension import DeviceArray
+
 import scico.numpy as snp
 from scico._generic_operators import Operator
 from scico.numpy.util import is_nested
@@ -27,10 +29,10 @@
 class CircularConvolve(LinearOperator):
     r"""A circular convolution linear operator.
 
-    This linear operator implements circular, n-dimensional convolution
-    via pointwise multiplication in the DFT domain. In its simplest form,
-    it implements a single convolution and can be represented by linear
-    operator :math:`H` such that
+    This linear operator implements circular, multi-dimensional
+    convolution via pointwise multiplication in the DFT domain. In its
+    simplest form, it implements a single convolution and can be
+    represented by linear operator :math:`H` such that
 
     .. math::
        H \mb{x} = \mb{h} \ast \mb{x} \;,
@@ -83,7 +85,7 @@ def __init__(
         ndims: Optional[int] = None,
         input_dtype: DType = snp.float32,
         h_is_dft: bool = False,
-        h_center: Optional[JaxArray] = None,
+        h_center: Optional[Union[JaxArray, Sequence, float, int]] = None,
         jit: bool = True,
         **kwargs,
     ):
@@ -99,7 +101,8 @@ def __init__(
             h_is_dft: Flag indicating whether `h` is in the DFT domain.
             h_center: Array of length `ndims` specifying the center of
                the filter. Defaults to the upper left corner, i.e.,
-               `h_center = [0, 0, ..., 0]`, may be noninteger.
+               `h_center = [0, 0, ..., 0]`, may be noninteger. May be a
+               ``float`` or ``int`` if `h` is one-dimensional.
             jit:  If ``True``, jit the evaluation, adjoint, and gram
                functions of the LinearOperator.
         """
@@ -124,7 +127,18 @@ def __init__(
             output_dtype = result_type(h.dtype, input_dtype)
 
             if self.h_center is not None:
-                offset = -self.h_center
+                if isinstance(self.h_center, DeviceArray):
+                    offset = -self.h_center
+                else:
+                    # support float or int values for h_center
+                    if isinstance(self.h_center, (float, int)):
+                        offset = -snp.array(
+                            [
+                                self.h_center,
+                            ]
+                        )
+                    else:  # support list/tuple values for h_center
+                        offset = -snp.array(self.h_center)
                 shifts: Tuple[Array, ...] = np.ix_(
                     *tuple(
                         np.exp(-1j * k * 2 * np.pi * np.fft.fftfreq(s))

scico/test/linop/test_circconv.py

@@ -123,6 +123,27 @@ def test_matches_convolve(self, input_dtype, jit):
         desired = A @ x
         np.testing.assert_allclose(actual, desired, atol=1e-6)
 
+    @pytest.mark.parametrize(
+        "center",
+        [
+            1,
+            [
+                1,
+            ],
+            snp.array([2]),
+        ],
+    )
+    def test_center(self, center):
+        x, key = uniform(minval=-1, maxval=1, shape=(16,), key=self.key)
+        h = snp.array([0.5, 1.0, 0.25])
+        A = CircularConvolve(h=h, input_shape=x.shape, h_center=center)
+        B = CircularConvolve(h=h, input_shape=x.shape)
+        if isinstance(center, int):
+            shift = -center
+        else:
+            shift = -center[0]
+        np.testing.assert_allclose(A @ x, snp.roll(B @ x, shift), atol=1e-5)
+
     @pytest.mark.parametrize("axes_shape_spec", SHAPE_SPECS)
     @pytest.mark.parametrize("input_dtype", [np.float32, np.complex64])
     @pytest.mark.parametrize("jit_old_op", [True, False])