Revert "parent() is now static function"

This reverts commit c58ca70.

Author: Nathan Shreve

vpr/src/route/binary_heap.cpp

@@ -4,7 +4,8 @@
 // child indices of a heap
 static inline size_t left(size_t i) { return i << 1; }
 static inline size_t right(size_t i) { return (i << 1) + 1; }
-static inline size_t parent(size_t i) { return i >> 1; }
+
+inline size_t BinaryHeap::parent(size_t i) const { return i >> 1; }
 
 bool BinaryHeap::is_valid() const {
     if (heap_.empty()) {

vpr/src/route/binary_heap.h

@@ -11,6 +11,7 @@ class BinaryHeap : public KAryHeap {
 
   private:
     void sift_down(size_t hole) final;
+    size_t parent(size_t i) const final;
 };
 
 #endif //VTR_BINARY_HEAP_H

vpr/src/route/four_ary_heap.cpp

@@ -2,7 +2,8 @@
 #include "vtr_log.h"
 
 static inline size_t first_child(size_t i) { return (i << 2) - 2; }
-static inline size_t parent(size_t i) { return (i + 2) >> 2; }
+
+inline size_t FourAryHeap::parent(size_t i) const { return (i + 2) >> 2; }
 
 inline size_t FourAryHeap::smallest_child(size_t i) const {
     // Returns first_child(i) if i has no children

vpr/src/route/four_ary_heap.h

@@ -11,6 +11,7 @@ class FourAryHeap : public KAryHeap {
 
   private:
     void sift_down(size_t hole) final;
+    size_t parent(size_t i) const final;
     size_t smallest_child(size_t i) const;
 };
 

vpr/src/route/k_ary_heap.h

@@ -37,6 +37,7 @@ class KAryHeap : public HeapInterface {
     void prune_heap();
 
     virtual void sift_down(size_t hole) = 0;
+    virtual size_t parent(size_t i) const = 0;
 
     HeapStorage storage_;