Changeset 2a5345b for src/BasicTypes-gen.cpp

Timestamp:

Jan 25, 2025, 5:59:05 PM (11 months ago)

Author:

Fangren Yu <f37yu@…>

Branches:

master

Children:

11f92fac

Parents:

1fb0a883

Message:

try to fix cost table one more time, add some comments

File:

• src/BasicTypes-gen.cpp (modified) (3 diffs)

src/BasicTypes-gen.cpp

@@ -135 +135 @@
 static Kind commonTypeMatrix[NUMBER_OF_BASIC_TYPES][NUMBER_OF_BASIC_TYPES];
 
-// Fangren explain shortest cost algorithm.
+// Compute the minimal conversion costs using Dijkstra's algorithm
 void generateCosts( int row ) {
         bool seen[NUMBER_OF_BASIC_TYPES] = { false /*, ... */ };
@@ -176 +176 @@
 
                 // traverse children
-                // Fangren explain "max"
+                // any conversion should have a cost of at least 1, even if between types of equal rank
                 int i = graph[col].left;
                 if ( i == -1 ) continue;                                                // leaf
@@ -191 +191 @@
 } // generateCosts
 
-// Fangren explain this routine if you can.
+// Note: this algorithm is not general.
+// It relies on the specific structure of the conversion graph.
+// When the common type is not one of the two given types, we should always have a real and a complex floating point type,
+// in which case the common type is the next complex type ranked higher than the real type.
 void generateCommonType( int row, int col ) {                   // row <= col
         if ( costMatrix[row][col] >= 0 ) {