zhiics commented on a change in pull request #4886: [WIP][POC]First pass a
defining at non-recursive Graph Vistor and Rewriter
URL: https://github.com/apache/incubator-tvm/pull/4886#discussion_r401249373
##########
File path: src/relay/ir/expr_functor.cc
##########
@@ -29,8 +29,158 @@
#include <tvm/relay/expr_functor.h>
#include <tvm/relay/pattern_functor.h>
+#include <stack>
+
namespace tvm {
namespace relay {
+/*!
+ * \brief A function to iteratively traverse dataflow regions of a graph
+ *
+ * ExpandDatflow manually manages a stack and performs DFS to determine the
processing
+ * order of nodes in an input graph.
+ *
+ * If it finds a dataflow node (Call, Tuple, TupleGetItem), it checks if the
arguments to that node
+ * need to be processed via fcheck_visited. If so, the function pushes those
arguments to the stack
+ * and continues iteratively to process the top of the stack. When it finds a
node that doesn't
+ * match the dataflow types, or a node who's inputs have all been processed,
it visits the current
+ * leaf via fvisit_leaf.
+ *
+ * This function should be used internally to other classes to implement
mixed-mode traversals. The
+ * expectation is that fvisit_leaf will perform recursive analysis within
mixed-mode traversal if it
+ * hits a non-dataflow node.
+ *
+ * fcheck_visited and fvisit_leaf are templated to encourage compiler inlining.
+ */
+template <typename FCheckVisited, typename FVisitLeaf>
+void ExpandDataflow(Expr expr, FCheckVisited fcheck_visited, FVisitLeaf
fvisit_leaf) {
+ std::stack<std::pair<Expr, bool>> stack;
+ auto fpush_to_stack = [&fcheck_visited, &stack](const Expr& expr) {
+ // The second state of the stack indicate whether the child has been
+ // expanded in the pre-order.
+ // NOTE: function will be inlined.
+ if (!fcheck_visited(expr)) {
+ stack.push({expr, false});
+ }
+ };
+ fpush_to_stack(expr);
+ while (stack.size() > 0) {
+ auto node = stack.top().first;
+ if (fcheck_visited(expr)) {
+ // if this node was visited through another path
+ // after being added to the stack ignore it.
+ stack.pop();
+ } else if (stack.top().second) {
+ // all the children have already been expanded.
+ // we can just run post order visit on it.
+ fvisit_leaf(node);
+ stack.pop();
+ } else if (const CallNode* op = node.as<CallNode>()) {
+ // mark expanded = true
+ stack.top().second = true;
+ // push the children to the stack in reverse order
+ // to match recursive processing order
+ for (auto it = op->args.rbegin(); it != op->args.rend(); ++it) {
+ fpush_to_stack(*it);
+ }
+ fpush_to_stack(op->op);
+ } else if (const TupleNode* op = node.as<TupleNode>()) {
+ stack.top().second = true;
+ // push the children to the stack in reverse order
+ // to match recursive processing order
+ for (auto it = op->fields.rbegin(); it != op->fields.rend(); ++it) {
+ fpush_to_stack(*it);
+ }
+ } else if (const TupleGetItemNode* op = node.as<TupleGetItemNode>()) {
+ stack.top().second = true;
+ fpush_to_stack(op->tuple);
+ } else {
+ // No need to expand the children directly run visit.
+ fvisit_leaf(node);
+ stack.pop();
+ }
+ }
+}
+
+DataflowVisitor::DataflowVisitor(int visit_limit) {
+ CHECK(visit_limit > 0) << "Dataflow visit limit must be greater than 0";
+ CHECK(visit_limit < 10) << "Dataflow visit limit must be less than 10";
Review comment:
Could you explain why it must be less than 10 here? I think I don't well
understand the functionality of `visit_limit`. So we will just stop visiting if
it reaches the limit?
----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
For queries about this service, please contact Infrastructure at:
[email protected]
With regards,
Apache Git Services
