Implement np.linspace in fake_numpy

arraycontext/fake_numpy.py

@@ -23,6 +23,9 @@
 """
 
 
+import operator
+from typing import Any
+
 import numpy as np
 
 from arraycontext.container import NotAnArrayContainerError, serialize_container
@@ -100,6 +103,89 @@ def conjugate(self, x):
 
     conj = conjugate
 
+    # {{{ linspace
+
+    # based on
+    # https://github.com/numpy/numpy/blob/v1.25.0/numpy/core/function_base.py#L24-L182
+
+    def linspace(self, start, stop, num=50, endpoint=True, retstep=False, dtype=None,
+                axis=0):
+        num = operator.index(num)
+        if num < 0:
+            raise ValueError("Number of samples, %s, must be non-negative." % num)
+        div = (num - 1) if endpoint else num
+
+        # Convert float/complex array scalars to float, gh-3504
+        # and make sure one can use variables that have an __array_interface__,
+        # gh-6634
+
+        if isinstance(start, self._array_context.array_types):
+            raise NotImplementedError("start as an actx array")
+        if isinstance(stop, self._array_context.array_types):
+            raise NotImplementedError("stop as an actx array")
+
+        start = np.array(start) * 1.0
+        stop = np.array(stop) * 1.0
+
+        dt = np.result_type(start, stop, float(num))
+        if dtype is None:
+            dtype = dt
+            integer_dtype = False
+        else:
+            integer_dtype = np.issubdtype(dtype, np.integer)
+
+        delta = stop - start
+
+        y = self.arange(0, num, dtype=dt).reshape((-1,) + (1,) * delta.ndim)
+
+        if div > 0:
+            step = delta / div
+            #any_step_zero = _nx.asanyarray(step == 0).any()
+            any_step_zero = self._array_context.to_numpy((step == 0)).any()
+            if any_step_zero:
+                delta_actx = self._array_context.from_numpy(delta)
+
+                # Special handling for denormal numbers, gh-5437
+                y = y / div
+                y = y * delta_actx
+            else:
+                step_actx = self._array_context.from_numpy(step)
+                y = y * step_actx
+        else:
+            delta_actx = self._array_context.from_numpy(delta)
+            # sequences with 0 items or 1 item with endpoint=True (i.e. div <= 0)
+            # have an undefined step
+            step = np.NaN
+            # Multiply with delta to allow possible override of output class.
+            y = y * delta_actx
+
+        y += start
+
+        # FIXME reenable, without in-place ops
+        # if endpoint and num > 1:
+        #     y[-1, ...] = stop
+
+        if axis != 0:
+            # y = _nx.moveaxis(y, 0, axis)
+            raise NotImplementedError("axis != 0")
+
+        if integer_dtype:
+            y = self.floor(y)  # pylint: disable=no-member
+
+        # FIXME: Use astype
+        # https://github.com/inducer/pytato/issues/456
+        if retstep:
+            return y, step
+            #return y.astype(dtype), step
+        else:
+            return y
+            #return y.astype(dtype)
+
+    # }}}
+
+    def arange(self, *args: Any, **kwargs: Any):
+        raise NotImplementedError
+
 # }}}
 
 
@@ -180,6 +266,7 @@ def norm(self, ary, ord=None):
             return actx.np.sum(abs(ary)**ord)**(1/ord)
         else:
             raise NotImplementedError(f"unsupported value of 'ord': {ord}")
+
 # }}}
 
 

arraycontext/impl/pytato/fake_numpy.py

@@ -22,6 +22,7 @@
 THE SOFTWARE.
 """
 from functools import partial, reduce
+from typing import Any
 
 import numpy as np
 

test/test_arraycontext.py

@@ -1580,6 +1580,28 @@ def test_compile_anonymous_function(actx_factory):
         42)
 
 
+@pytest.mark.parametrize(
+        ("args", "kwargs"), [
+            ((1, 2, 10), {}),
+            ((1, 2, 10), {"endpoint": False}),
+            ((1, 2, 10), {"endpoint": True}),
+            ((2, -3, 20), {}),
+            ((1, 5j, 20), {"dtype": np.complex128}),
+            ((1, 5, 20), {"dtype": np.complex128}),
+            ((1, 5, 20), {"dtype": np.int32}),
+            ])
+def test_linspace(actx_factory, args, kwargs):
+    if "Jax" in actx_factory.__class__.__name__:
+        pytest.xfail("jax actx does not have arange")
+
+    actx = actx_factory()
+
+    actx_linspace = actx.to_numpy(actx.np.linspace(*args, **kwargs))
+    np_linspace = np.linspace(*args, **kwargs)
+
+    assert np.allclose(actx_linspace, np_linspace)
+
+
 if __name__ == "__main__":
     import sys
     if len(sys.argv) > 1: