rr_graph: use median instead of mode for C/R Node values

Signed-off-by: Alessandro Comodi <[email protected]>

Author: acomodi

libs/libvtrutil/src/vtr_math.cpp

@@ -1,4 +1,5 @@
 #include <map>
+#include <algorithm>
 
 #include "vtr_assert.h"
 #include "vtr_error.h"
@@ -20,6 +21,19 @@ int ipow(int base, int exp) {
     return result;
 }
 
+float median(std::vector<float> vector) {
+    VTR_ASSERT(vector.size() > 0);
+
+    std::sort(vector.begin(), vector.end());
+
+    auto size = vector.size();
+    if (size % 2 == 0) {
+        return (float)(vector[size / 2 - 1] + vector[size / 2]) / 2;
+    }
+
+    return (float)vector[size / 2];
+}
+
 /* Performs linear interpolation or extrapolation on the set of (x,y) values specified by the xy_map.
  * A requested x value is passed in, and we return the interpolated/extrapolated y value at this requested value of x.
  * Meant for maps where both key and element are numbers.

libs/libvtrutil/src/vtr_math.h

@@ -2,6 +2,7 @@
 #define VTR_MATH_H
 
 #include <map>
+#include <vector>
 #include <cmath>
 
 #include "vtr_assert.h"
@@ -10,6 +11,9 @@ namespace vtr {
 /*********************** Math operations *************************************/
 int ipow(int base, int exp);
 
+//Returns the median of an input vector.
+float median(std::vector<float> vector);
+
 template<typename X, typename Y>
 Y linear_interpolate_or_extrapolate(const std::map<X, Y>* xy_map, X requested_x);
 

vpr/src/route/rr_graph_indexed_data.cpp

@@ -5,6 +5,7 @@
 #include "vtr_assert.h"
 #include "vtr_log.h"
 #include "vtr_memory.h"
+#include "vtr_math.h"
 
 #include "vpr_types.h"
 #include "vpr_error.h"
@@ -390,8 +391,9 @@ static void load_rr_indexed_data_T_values() {
             auto switch_T_total_histogram = build_histogram(switch_T_total[cost_index], 10);
             auto switch_Cinternal_total_histogram = build_histogram(switch_Cinternal_total[cost_index], 10);
 
-            float Rnode = get_histogram_mode(R_total_histogram);
-            float Cnode = get_histogram_mode(C_total_histogram);
+            // Sort Rnode and Cnode
+            float Cnode = vtr::median(C_total[cost_index]);
+            float Rnode = vtr::median(R_total[cost_index]);
             float Rsw = get_histogram_mode(switch_R_total_histogram);
             float Tsw = get_histogram_mode(switch_T_total_histogram);
             float Cinternalsw = get_histogram_mode(switch_Cinternal_total_histogram);