[Lang] Fix undef BijectiveLayout and add scalar layout support (#3105)

include/tvm/data_layout.h

@@ -94,12 +94,13 @@ class Layout;
 // Internal node container Buffer
 class LayoutNode : public Node {
  public:
-  /*! \brief string representation of layout */
+  /*! \brief string representation of layout, "" for scalar. */
   std::string name;
   /*! \brief specify each axis of the layout,
    *   in which the variable name is the name of the axis.
    *   The IterVar's extent indicates the size of the axis,
    *   it is a variable for a primal axis, but a constant for a subordinate axis.
+   *   Empty for scalar's layout.
    */
   Array<IterVar> axes;
 
@@ -122,6 +123,7 @@ class LayoutNode : public Node {
  *  For example, NCHW16c can describe a 5-D tensor of
  *  [batch_size, channel, height, width, channel_block].
  *  Here subordinate axis channel_block=16 is the factor size of the primal axis C (channel).
+ *  Layout for scalar is defined, while both its name and axes have size 0.
  */
 class Layout : public NodeRef {
  public:
@@ -175,7 +177,7 @@ class Layout : public NodeRef {
    *        that starts at dimension \p pos and spans \p len dimensions
    *        (or until the end of the layout, whichever comes first).
    * \param pos The start position.
-   * \param len The length of the sub-layout.
+   * \param len The length of the sub-layout. if 0, return layout of scalar
    * \return A newly constructed Layout object.
    */
   Layout SubLayout(size_t pos, size_t len) const;

src/lang/data_layout.cc

@@ -88,12 +88,14 @@ Layout::Layout(const Array<IterVar>& axes) {
 }
 
 Layout::Layout(const std::string& name) { // NOLINT(*)
-  if (name.empty() || name == "__undef__") return;
+  if (name == "__undef__") return;
 
   node_ = make_node<LayoutNode>();
   LayoutNode *node = operator->();
   node->name = name;
 
+  if (name.empty()) return;  // scalar
+
   // parse layout string
   int32_t factor = 0;
   for (char c : name) {
@@ -146,6 +148,7 @@ Layout LayoutNode::make(const std::string& layout) {
 
 Layout Layout::SubLayout(size_t pos, size_t len) const {
   if (!defined() || pos > ndim()) return Layout::Undef();
+  if (len == 0) return Layout(Array<IterVar>());
   if (pos + len > ndim()) len = ndim() - pos;
   Array<IterVar> new_layout;
   const auto axes = operator->()->axes;
@@ -195,6 +198,10 @@ int32_t Layout::FactorOf(const LayoutAxis& axis) const {
 inline bool GetStoreRule(Array<Expr>* rule,
                          const Layout& src_layout,
                          const Layout& dst_layout) {
+  if (!src_layout.defined() || src_layout.name().empty() ||
+      !dst_layout.defined() || dst_layout.name().empty()) {
+    return false;
+  }
   for (size_t i = 0; i < dst_layout.ndim(); ++i) {
     const auto& store_axis = dst_layout[i];
     const IterVar& store_axis_impl = dst_layout->axes[i];

src/relay/pass/alter_op_layout.h

@@ -99,13 +99,17 @@ inline Array<Array<Layout> > BinaryBroadcastLayout(const Attrs& attrs,
                   layouts[defined_idx].SubLayout(
                       old_in_shapes[defined_idx].size() - old_in_shapes[undef_idx].size(),
                       old_in_shapes[undef_idx].size()));
-      return Array<Array<Layout> > {layouts, {layouts[defined_idx]}};
+      return Array<Array<Layout> >{layouts, {layouts[defined_idx]}};
     } else {
       // only know the tensor with smaller dimensions,
       // so we cannot infer the final broadcasted output.
       // fails in this case.
-      return Array<Array<Layout> > {{Layout::Undef()}, {Layout::Undef()}};
+      return Array<Array<Layout> >{{Layout::Undef()}, {Layout::Undef()}};
     }
+  } else if (layouts[0].defined() && layouts[1].defined() &&
+            (layouts[0].ndim() == 0 || layouts[1].ndim() == 0)) {
+    int scalar = layouts[0].ndim() == 0 ? 0 : 1;
+    return Array<Array<Layout> >{layouts, {layouts[1-scalar]}};
   } else {
     // try to broadcast the tensors to the larger dimension
     int large_idx = layouts[0].ndim_primal() >= layouts[1].ndim_primal() ? 0 : 1;

tests/python/relay/test_pass_alter_op_layout.py

@@ -57,7 +57,7 @@ def test_alter_op():
     b = expected()
     b = infer_type(b)
 
-    assert(alpha_equal(a, b))
+    assert alpha_equal(a, b), "Actual = \n" + str(a)
 
 
 def test_alter_return_none():
@@ -81,7 +81,7 @@ def test_alter_return_none():
 
     b = before()
     b = infer_type(b)
-    assert(alpha_equal(a, b))
+    assert alpha_equal(a, b), "Actual = \n" + str(a)
     assert(called[0])
 
 
@@ -147,7 +147,7 @@ def test_alter_layout():
     b = expected()
     b = infer_type(b)
 
-    assert(alpha_equal(a, b))
+    assert alpha_equal(a, b), "Actual = \n" + str(a)
 
 
 def test_alter_layout_dual_path():
@@ -213,7 +213,7 @@ def test_alter_layout_dual_path():
     b = expected()
     b = infer_type(b)
 
-    assert(alpha_equal(a, b))
+    assert alpha_equal(a, b), "Actual = \n" + str(a)
 
 def test_alter_layout_resnet():
     """Test alternating the layout of a residual block
@@ -273,7 +273,7 @@ def test_alter_layout_resnet():
     b = expected()
     b = infer_type(b)
 
-    assert(alpha_equal(a, b))
+    assert alpha_equal(a, b), "Actual = \n" + str(a)
 
 
 def test_alter_layout_broadcast_op():
@@ -323,7 +323,7 @@ def test_alter_layout_broadcast_op():
     b = expected()
     b = infer_type(b)
 
-    assert(alpha_equal(a, b))
+    assert alpha_equal(a, b), "Actual = \n" + str(a)
 
 def test_alter_layout_scalar():
     """Test alternating the layout of a conv2d.
@@ -370,7 +370,7 @@ def test_alter_layout_scalar():
     b = expected()
     b = infer_type(b)
 
-    assert(alpha_equal(a, b))
+    assert alpha_equal(a, b), "Actual = \n" + str(a)
 
 def test_alter_layout_concatenate():
     """ """
@@ -425,7 +425,7 @@ def test_alter_layout_concatenate():
     b = expected()
     b = infer_type(b)
 
-    assert(alpha_equal(a, b))
+    assert alpha_equal(a, b), "Actual = \n" + str(a)
 
 
 def test_alter_layout_nchw_upsamping_op():
@@ -469,7 +469,7 @@ def test_alter_layout_nchw_upsamping_op():
     b = expected()
     b = infer_type(b)
 
-    assert(alpha_equal(a, b))
+    assert alpha_equal(a, b), "Actual = \n" + str(a)
 
 
 def test_alter_layout_strided_slice():
@@ -511,7 +511,7 @@ def test_alter_layout_strided_slice():
     b = expected()
     b = infer_type(b)
 
-    assert(alpha_equal(a, b))
+    assert alpha_equal(a, b), "Actual = \n" + str(a)
 
 
 if __name__ == "__main__":

tests/python/unittest/test_lang_data_layout.py

@@ -52,6 +52,12 @@ def test_layout():
 def test_bilayout_convertible():
     # not convertible
     assert tvm.bijective_layout("NCHW", "ABCD") is None
+    assert tvm.bijective_layout("__undef__", "NCHW") is None
+    assert tvm.bijective_layout("NCHW", "__undef__") is None
+    assert tvm.bijective_layout("__undef__", "__undef__") is None
+    assert tvm.bijective_layout("", "NCHW") is None
+    assert tvm.bijective_layout("NCHW", "") is None
+    assert tvm.bijective_layout("", "") is None
     # convertible
     assert tvm.bijective_layout("NCHW", "NCHW16c") is not None