widelands-dev team mailing list archive

[Notabilis <notabilis27@xxxxxx>]

Notabilis has proposed merging lp:~widelands-dev/widelands/bug-1811030-desync-ai into lp:widelands.

Commit message:
Replacing logic_rand() with std::rand() in seafaring code of AI.
Should fix desyncs while network gaming.


Requested reviews:
  Widelands Developers (widelands-dev)

For more details, see:
https://code.launchpad.net/~widelands-dev/widelands/bug-1811030-desync-ai/+merge/361689

Calls of logic_rand() have to be done on all participants of a network game. Since the AI code is only executed on the host, calling logic_rand() leads to different random numbers on the participants computers later on, resulting in desynchronized games.
-- 
Your team Widelands Developers is requested to review the proposed merge of lp:~widelands-dev/widelands/bug-1811030-desync-ai into lp:widelands.

=== modified file 'src/ai/defaultai_seafaring.cc'
--- src/ai/defaultai_seafaring.cc	2018-09-04 15:48:47 +0000
+++ src/ai/defaultai_seafaring.cc	2019-01-11 21:07:24 +0000
@@ -455,7 +455,7 @@
 }
 
 Widelands::IslandExploreDirection DefaultAI::randomExploreDirection() {
-	return game().logic_rand() % 20 < 10 ? Widelands::IslandExploreDirection::kClockwise :
+	return std::rand() % 20 < 10 ? Widelands::IslandExploreDirection::kClockwise :
 	                                       Widelands::IslandExploreDirection::kCounterClockwise;
 }
 
@@ -486,7 +486,7 @@
 		    spot_score);
 
 		// we make a decision based on the score value and random
-		if (game().logic_rand() % 8 < spot_score) {
+		if (std::rand() % 8 < spot_score) {
 			// we build a port here
 			game().send_player_ship_construct_port(*so.ship, so.ship->exp_port_spaces().front());
 			so.last_command_time = gametime;
@@ -579,15 +579,15 @@
 	assert(possible_directions.size() >= new_teritory_directions.size());
 
 	// If only open sea (no unexplored sea) is found, we don't always divert the ship
-	if (new_teritory_directions.empty() && game().logic_rand() % 100 < 80) {
+	if (new_teritory_directions.empty() && std::rand() % 100 < 80) {
 		return false;
 	}
 
 	if (!possible_directions.empty() || !new_teritory_directions.empty()) {
 		const Direction direction =
 		   !new_teritory_directions.empty() ?
-		      new_teritory_directions.at(game().logic_rand() % new_teritory_directions.size()) :
-		      possible_directions.at(game().logic_rand() % possible_directions.size());
+		      new_teritory_directions.at(std::rand() % new_teritory_directions.size()) :
+		      possible_directions.at(std::rand() % possible_directions.size());
 		game().send_player_ship_scouting_direction(*so.ship, static_cast<WalkingDir>(direction));
 
 		log("%d: %s: exploration - breaking for %s sea, dir=%u\n", pn,