dsl: Tweak SpaceDimension lower bounds behaviour to use fewer registers

devito/types/dimension.py

@@ -457,6 +457,10 @@ class SpaceDimension(BasicDimension):
 
     is_Space = True
 
+    @property
+    def symbolic_min(self):
+        return sympy.S.Zero
+
 
 class TimeDimension(BasicDimension):
 

examples/seismic/tutorials/16_ader_fd.ipynb

@@ -5,7 +5,7 @@
    "id": "0",
    "metadata": {},
    "source": [
-    "# 15 - ADER-FD\n",
+    "# 16 - ADER-FD\n",
     "\n",
     "This notebook demonstrates the implementation of a finite-difference scheme for solving the first-order formulation of the acoustic wave equation using ADER (Arbitrary-order-accuracy via DERivatives) time integration. This enables a temporal discretisation up the order of the spatial discretisation, whilst preventing the grid-grid decoupling (often referred to as checkerboarding) associated with solving first-order systems of equations on a single finite-difference grid.\n",
     "\n",

examples/userapi/02_apply.ipynb

@@ -8,9 +8,9 @@
     "\n",
     "This tutorial describes three fundamental user APIs:\n",
     "\n",
-    "* Operator.apply\n",
-    "* Operator.arguments\n",
-    "* Operator.estimate_memory\n",
+    "* `Operator.apply`\n",
+    "* `Operator.arguments`\n",
+    "* `Operator.estimate_memory`\n",
     "\n",
     "We will use a trivial `Operator` that, at each time step, increments by 1 all points in the physical domain."
    ]
@@ -57,7 +57,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Under the hood, some code has been generated (`print(op)` to display the generated code), JIT-compiled, and executed. Since no additional arguments have been passed, `op` has used `u` as input. We can verify that the content of `u.data` is as expected"
+    "Under the hood, some code has been generated, JIT-compiled, and executed. Note that one can print `op.ccode` to display the generated code. Since no additional arguments have been passed, `op` has used `u` as input. We can verify that the content of `u.data` is as expected"
    ]
   },
   {
@@ -162,7 +162,7 @@
    "source": [
     "`'u'` stores a pointer to the allocated data; `'timers'` stores a pointer to a data structure used for C-level performance profiling.\n",
     "\n",
-    "One may want to replace some of these default arguments. For example, we could increase the minimum iteration point along the spatial Dimensions `x` and `y`, and execute only the very first timestep:"
+    "One may want to replace some of these default arguments. For example, we could reduce the maximum iteration point along the spatial Dimensions `x` and `y`, and execute only the very first timestep:"
    ]
   },
   {
@@ -174,14 +174,14 @@
      "name": "stderr",
      "output_type": "stream",
      "text": [
-      "Operator `Kernel` run in 0.00 s\n"
+      "Operator `Kernel` ran in 0.01 s\n"
      ]
     }
    ],
    "source": [
     "#NBVAL_IGNORE_OUTPUT\n",
     "u.data[:] = 0.  # Explicit reset to initial value\n",
-    "summary = op.apply(x_m=2, y_m=2, time_M=0)"
+    "summary = op.apply(x_M=1, y_M=1, time_M=0)"
    ]
   },
   {
@@ -204,10 +204,10 @@
        "       [0., 0., 0., 0.],\n",
        "       [0., 0., 0., 0.]],\n",
        "\n",
-       "      [[0., 0., 0., 0.],\n",
-       "       [0., 0., 0., 0.],\n",
-       "       [0., 0., 1., 1.],\n",
-       "       [0., 0., 1., 1.]],\n",
+       "      [[1., 1., 1., 0.],\n",
+       "       [1., 1., 1., 0.],\n",
+       "       [1., 1., 1., 0.],\n",
+       "       [0., 0., 0., 0.]],\n",
        "\n",
        "      [[0., 0., 0., 0.],\n",
        "       [0., 0., 0., 0.],\n",
@@ -228,12 +228,14 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
+    "Side note: in practice, iterating over a subset of the grid by directly overriding the minimum and maximum values of a dimension is not advised. Instead, a `SubDomain` interface is available for this purpose (detailed in tutorial `03_subdomains`).\n",
+    "\n",
     "Given a generic `Dimension` `d`, the naming convention is such that:\n",
     "\n",
     "* `d_m` is the minimum iteration point\n",
     "* `d_M` is the maximum iteration point\n",
     "\n",
-    "Hence, `op.apply(..., d_m=4, d_M=7, ...)` will run `op` in the compact interval `[4, 7]` along `d`. For historical reasons, `d=...` aliases to `d_M=...`; in many Devito examples it happens to see `op.apply(..., time=10, ...)` -- this is just equivalent to `op.apply(..., time_M=10, ...)`.\n",
+    "Hence, `op.apply(..., d_m=4, d_M=7, ...)` will run `op` in the compact interval `[4, 7]` along `d`. For historical reasons, `d=...` aliases to `d_M=...`; in many Devito examples it happens to see `op.apply(..., time=10, ...)` -- this is just equivalent to `op.apply(..., time_M=10, ...)`. `SpaceDimension`s, such as those attached to a `Grid` do not have a `d_m`, as these dimensions will essentially always be indexed from zero to `d_M` along each axis.\n",
     "\n",
     "If we try to specify an invalid iteration extreme, Devito will raise an exception."
    ]

tests/test_dimension.py

@@ -754,7 +754,7 @@ def test_arrays_defined_over_subdims(self):
         op = Operator([Eq(a[xi], 1), Eq(f, f + a[xi + 1], subdomain=grid.interior)],
                       opt=('advanced', {'openmp': False}))
 
-        assert len(op.parameters) == 6
+        assert len(op.parameters) == 5
         # neither `x_size` nor `xi_size` are expected here
         assert not any(i.name in ('x_size', 'xi_size') for i in op.parameters)
         # Try running it -- regardless of what it will produce, this should run
@@ -779,8 +779,7 @@ def test_expandingbox_like(self, opt):
 
         op = Operator(eqn, opt=opt)
 
-        op.apply(time=3, x_m=2, x_M=5, y_m=2, y_M=5,
-                 x_ltkn0=0, x_rtkn0=0, y_ltkn0=0, y_rtkn0=0)
+        op.apply(time=3, x_ltkn0=2, x_rtkn0=2, y_ltkn0=2, y_rtkn0=2)
 
         assert np.all(u.data[0, 2:-2, 2:-2] == 4.)
         assert np.all(u.data[1, 2:-2, 2:-2] == 3.)

tests/test_dle.py

@@ -146,7 +146,7 @@ def test_cache_blocking_structure_subdims():
     # zi is rebuilt with name z, so check symbolic max and min are preserved
     # Also check the zi was rebuilt
     assert not tree[4].dim.is_Block and tree[4].dim is not zi and\
-        str(tree[4].dim.symbolic_min) == 'z_m + z_ltkn0' and\
+        str(tree[4].dim.symbolic_min) == 'z_ltkn0' and\
         str(tree[4].dim.symbolic_max) == 'z_M - z_rtkn0' and\
         tree[4].dim.parent is z
 
@@ -536,7 +536,7 @@ def test_cache_blocking_imperfect_nest(blockinner):
     assert trees[0].root.dim.is_Block
     assert trees[1].root.dim.is_Block
     assert op1.parameters[7] is trees[0][0].step
-    assert op1.parameters[10] is trees[0][1].step
+    assert op1.parameters[9] is trees[0][1].step
 
     u.data[:] = 0.2
     v.data[:] = 1.5
@@ -1380,7 +1380,7 @@ def test_nested_cache_blocking_structure_subdims(self, blocklevels):
 
         if blocklevels == 1:
             assert not tree[4].dim.is_Block and tree[4].dim is not zi and\
-                str(tree[4].dim.symbolic_min) == 'z_m + z_ltkn0' and\
+                str(tree[4].dim.symbolic_min) == 'z_ltkn0' and\
                 str(tree[4].dim.symbolic_max) == 'z_M - z_rtkn0' and\
                 tree[4].dim.parent is z
         elif blocklevels == 2:
@@ -1391,7 +1391,7 @@ def test_nested_cache_blocking_structure_subdims(self, blocklevels):
             assert tree[5].dim.is_Block and tree[5].dim.parent is tree[3].dim and\
                 tree[5].dim.root is y
             assert not tree[6].dim.is_Block and tree[6].dim is not zi and\
-                str(tree[6].dim.symbolic_min) == 'z_m + z_ltkn0' and\
+                str(tree[6].dim.symbolic_min) == 'z_ltkn0' and\
                 str(tree[6].dim.symbolic_max) == 'z_M - z_rtkn0' and\
                 tree[6].dim.parent is z