diff --git a/src/main.odin b/src/main.odin
index 1f00267..6545ac7 100644
--- a/src/main.odin
+++ b/src/main.odin
@@ -43,7 +43,7 @@ distance :: proc(x, y: int) -> int {
 }
 
 penalize :: proc(d: int) -> int {
-	return math.min(-3 * d, 0)
+	return math.min(d, 0)
 }
 
 // side-effect: reads global `items`
@@ -71,6 +71,7 @@ generate_population :: proc() -> (res: Population) {
 
 destroy_population :: proc(pop: ^Population) {
 	for &chrom in pop {
+		if chrom.free_pointer {continue}
 		bit_array.destroy(&chrom)
 	}
 }
@@ -233,28 +234,42 @@ elitism_survivor_selection :: proc(
 	offspring: ^Population,
 	parent_fitnesses: []int,
 	offspring_fitnesses: []int,
-) -> (
-	res: Population,
-) {
+) -> Population {
+	Index_Fitness :: struct {
+		idx:       int,
+		fitness:   int,
+		is_parent: bool,
+	}
+
 	combined_size := POPULATION_SIZE * 2
-	combined_fitnesses := make([]int, combined_size)
-	defer delete(combined_fitnesses)
+	combined := make([]Index_Fitness, combined_size)
+	defer delete(combined)
 
-	copy(combined_fitnesses[:POPULATION_SIZE], parent_fitnesses)
-	copy(combined_fitnesses[POPULATION_SIZE:], offspring_fitnesses)
+	for i in 0 ..< POPULATION_SIZE {
+		combined[i] = {i, parent_fitnesses[i], true}
+		combined[POPULATION_SIZE + i] = {i, offspring_fitnesses[i], false}
+	}
 
-	slice.sort(combined_fitnesses)
+	slice.sort_by(combined[:], proc(a, b: Index_Fitness) -> bool {
+		return a.fitness > b.fitness
+	})
 
-	for &s, i in res {
-		if i < POPULATION_SIZE {
-			s = parents[i]
-		} else {
-			s = offspring[i - POPULATION_SIZE]
+	survivors: Population
+	for i in 0 ..< POPULATION_SIZE {
+		entry := combined[i]
+		source := entry.is_parent ? &parents[entry.idx] : &offspring[entry.idx]
+
+		// Create NEW bit array and copy bits
+		survivors[i] = bit_array.create(NUMBER_OF_ITEMS)^
+		for j in 0 ..< NUMBER_OF_ITEMS {
+			bit_array.set(&survivors[i], j, bit_array.get(source, j))
 		}
 	}
-	return
+
+	return survivors
 }
 
+
 run_ga :: proc() {
 	population := generate_population()
 	defer destroy_population(&population)
@@ -279,7 +294,7 @@ run_ga :: proc() {
 				tot_weight += items[idx].weight
 			}
 			fmt.printfln(
-				"gen %d: best fitness=%d, profit=%d (capacity=%d)",
+				"gen %d: best fitness=%d, profit=%d, weight=%d (capacity=%d)",
 				gen,
 				f,
 				tot_profit,
@@ -336,11 +351,12 @@ run_ga :: proc() {
 }
 
 main :: proc() {
-	items, ok := read_data(DATA_FILE)
+	data, ok := read_data(DATA_FILE)
 	if !ok {
 		fmt.eprintln("failed to read data from", DATA_FILE)
 		return
 	}
+	items = data
 
 	fmt.println("running genetic algorithm for binary knapsack problem.")
 	fmt.printfln(