I'm taking my first AI class and attempting to implement the NegaMax algorithm into my code in c. I am using this algorithm to play the simple game of Nim, where each player removes 1-3 matches on their turn. The computer plays against itself here. However, I'm having trouble with the implementation. So far, I cannot seem to get the state to change for each recursive call of the function. I get an infinite loop where the best value goes from -INFINITY to INFINITY (where infinity is 999999). So the program never terminates because the state never gets to 1. I have trouble with recursion in general so if anyone can give me some hints as to where I should go with my code it would be greatly appreciated.
typedef struct State{
int m;
int eval;
}State;
State negaMax2(int state, int turn, State *best){
int move;
/*terminal state?*/
if(state == 1){
printf("Terminal state\n");
best->eval = turn;
return *best;
}
best->m = -INFINITY;
for(move = 1; move <= 3; move++) {
if (state - move > 0) { /* legal move */
int value = -1 * (negaMax2(state-move, turn, best)).m;
if (value > best->move){
best->eval = turn;
best->m = value;
}
}
}
return *best;
}
void playNim(int state) {
int turn = 0;
State *best;
best->eval = turn;
while (state != 1) {
int action = (negaMax2(state, turn, best)).m;
printf("%d: %s takes %d\n", state,
(turn==MAX ? "Max" : "Min"), action);
state = state - action;
turn = 1 - turn;
}
printf("1: %s looses\n", (turn==MAX ? "Max" : "Min"));
}
The culprit is this:
State *best;
best->eval = turn;
You are invoking undefined behavior here. You are trying to access eval while best has not yet been initialised (it is just declared).
You should consider doing something along the following lines:
State best;
best.eval = turn;
Related
To simplify the problem as much as possible, I have two functions, a parent that calls the child. Everything executes okay till it gets to the return of the child function. After that I get a Bus Error.
int main () {
game();
// this doesn't get executed and program fails with bus error
printf("Execute 2");
return 1;
}
int game () {
game_t GameInfo = {.level = 1, .score = 0, .playerCh = 0, .playerX = 1, .playerY = 1};
gameLevel(&GameInfo);
mvprintw(1,1, "Executed");
// code works up to here and get's executed properly
return 1;
};
void gameLevel (game_t *GameInfo) {
// determine the size of the game field
int cellCols = COLS / 3;
int cellRows = (LINES / 3) - 2;
GameInfo -> playerX = 1;
GameInfo -> playerY = 1;
generateMaze(0);
int solved = 0;
int level = GameInfo -> level;
// default player position
getPlayerDefault(GameInfo);
pthread_t enemies_th;
pthread_create(&enemies_th, NULL, enemies, (void *)GameInfo);
// enemies(&level);
while (solved == 0 && GameInfo -> collision != 1) {
printGameInfo(GameInfo);
noecho();
char move = getch();
echo();
if (GameInfo -> collision != 1) {
if (checkMoveValidity(move, GameInfo) == 1) {
solved = movePlayer(move, GameInfo);
if (solved == 1) {
break;
}
}
} else {
break;
}
}
if (solved == 1) {
pthread_cancel(enemies_th);
GameInfo->level++;
gameLevel(GameInfo);
} else {
// game over
pthread_cancel(enemies_th);
return;
}
}
Now, the code is much more complicated than here, but I think that shouldn't have any influence on this (?) as it executes properly, until the return statement. There is also ncurses and multithreading, quite complex custom structures, but it all works, up until that point. Any ideas ?
Tried putting print statements after each segment of code, everything worked up until this.
pthread_cancel() doesn't terminate the requested thread immediately. The only way to know that a cancelled thread has terminated is to call pthread_join(). If the thread is left running, it will interfere with use of the GameInfo variable in the next level of the game if the current level is solved, or may use the GameInfo variable beyond its lifetime if the current level was not solved and the main thread returns back to the main() function.
To make sure the old enemies thread has terminated, add calls to pthread_join() to the gameLevel() function as shown below:
if (solved == 1) {
pthread_cancel(enemies_th);
pthread_join(enemies_th);
GameInfo->level++;
gameLevel(GameInfo);
} else {
// game over
pthread_cancel(enemies_th);
pthread_join(enemies_th);
return;
}
The use of tail recursion in gameLevel() seems unnecessary. I recommend returning the solved value and letting the game() function start the next level:
In game():
while (gameLevel(&GameInfo)) {
GameInfo.level++;
}
In gameLevel():
int gameLevel(game_t *GameInfo) {
/* ... */
pthread_cancel(enemies_th);
pthread_join(enemies_th);
return solved;
}
I'm writing a program that will simulate a randomized race between runners who are climbing up a mountain where dwarf orcs (dorcs) are coming down the mountain to attack the runners. It begins with two runners named harold and timmy at the bottom of the mountain. The runners make their way up the mountain in randomized moves where they may make progress forward up the mountain, or they may slide back down the mountain. Dorcs are randomly generated, and they inflict damage on a runner if they collide. The simulation ends when one of the runners reaches the top of the mountain, or when both runners are dead.
I'm struggling with a part where I have to implement the actual race loop. Once the race is initialized, the race loop will iterate until the race is over. This happens when either a winner has been declared, or when all runners are dead.
Every iteration of the race loop will do the following:
with 30% probability, dynamically allocate a new dorc as an EntityType structure, and initialize it as follows:
(a) a dorc’s avatar is always “d”
(b) each dorc begins the race at the top of the mountain, which is at row 2
(c) with equal probability, the dorc may be placed either in the same column as timmy, or in the same column as the harold, or in the column exactly half-way between the two
(d) add the new dorc to the race’s array of dorcs
(e) using the pthread_create() function, create a thread for the new dorc, and save the thread pointer in the dorc’s entity structure; the function that each dorc thread will execute is the void* goDorc(void*) function that you will implement in a later step; the parameter to the goDorc() function will be the EntityType pointer that corresponds to that dorc
I guess I'm confused with the logic of how to approach this. I decided to make a function called isOver() to indicate if the race is over, and then a separate function called addDorc() to initialize the Dorc elements and do all the requirements above.
In isOver(), I attempt to add a dorc object to the dorcs array by doing addDorc(race); with every iteration of the race loop/if the race hasn't ended or no one died. But I keep getting the error:
control.c:82:3: error: too few arguments to function ‘addDorc’
addDorc(race);
The problem is I don't think I can manually declare all the parameters in addDorc() because some elements like the "path" argument are based on probability. As mentioned above, with equal probability, the dorc may be placed either in the same column as timmy, or in the same column as the harold, or in the column exactly half-way between the two. The issue is I don't know how to factor this random value when calling addDorc() and would appreciate some help. I also don't know if I'm doing the "with 30% probability, dynamically allocate a new dorc as an EntityType structure" correctly and would be grateful for some input on that as well.
defs.h
typedef struct {
pthread_t thr;
char avatar[MAX_STR];
int currPos;
int path;
} EntityType;
typedef struct {
EntityType ent;
char name[MAX_STR];
int health;
int dead;
} RunnerType;
typedef struct {
int numRunners;
RunnerType *runners[MAX_RUNNERS];
int numDorcs;
EntityType *dorcs[MAX_DORCS];
char winner[MAX_STR];
int statusRow;
sem_t mutex;
} RaceInfoType;
void launch();
int addDorc(RaceInfoType*, char*, int, int);
int isOver(RaceInfoType*);
void initRunners(RaceInfoType*);
int addRunner(RaceInfoType*, char*, char*, int, int, int, int);
int randm(int);
void *goRunner(void*);
void *goDorc(void*);
RaceInfoType *race;
control.c
void launch(){
race = malloc(sizeof(RaceInfoType));
race->numRunners = 0;
initRunners(race);
if (sem_init(&race->mutex, 0, 1) < 0) {
printf("semaphore initialization error\n");
exit(1);
}
strcpy(race->winner, " ");
srand((unsigned)time(NULL));
int i;
for(i = 0; i < race->numRunners; ++i){
pthread_create(&(race->runners[i]->ent.thr), NULL, goRunner, " ");
}
race->numDorcs = 0;
}
int addDorc(RaceInfoType* race, char *avatar, int path, int currPos){
if(race->numDorcs == MAX_DORCS){
printf("Error: Maximum dorcs already reached. \n");
return 0;
}
race->dorcs[race->numDorcs] = malloc(sizeof(EntityType));
int timmysColumn = race->dorcs[race->numDorcs]->currPos;
int haroldsColumn = race->dorcs[race->numDorcs]->currPos;
int halfwayColumn = (timmysColumn+haroldsColumn)/2;
int r = rand()%100;
pthread_t dorc;
if(r <= 30){
strcpy(race->dorcs[race->numDorcs]->avatar, "d");
race->dorcs[race->numDorcs]->currPos = 2;
if(r <= 33){
race->dorcs[race->numDorcs]->path = timmysColumn;
}else if(r <= 66){
race->dorcs[race->numDorcs]->path = haroldsColumn;
}else{
race->dorcs[race->numDorcs]->path = halfwayColumn;
}
pthread_create(&dorc, NULL, goDorc, " ");
}
race->numRunners++;
}
int isOver(RaceInfoType* race){
int i;
for(i = 0; i < race->numRunners; ++i){
if((race->winner != " ") || (race->runners[race->numRunners]->dead = 1)){
return 1;
}
addDorc(race);
return 0;
}
}
void initRunners(RaceInfoType* r){
addRunner(r, "Timmy", "T", 10, 35, 50, 0);
addRunner(r, "Harold", "H", 14, 35, 50, 0);
}
int addRunner(RaceInfoType* race, char *name, char *avatar, int path, int currPos, int health, int dead){
if(race->numRunners == MAX_RUNNERS){
printf("Error: Maximum runners already reached. \n");
return 0;
}
race->runners[race->numRunners] = malloc(sizeof(RunnerType));
strcpy(race->runners[race->numRunners]->name, name);
strcpy(race->runners[race->numRunners]->ent.avatar, avatar);
race->runners[race->numRunners]->ent.path = path;
race->runners[race->numRunners]->ent.currPos = currPos;
race->runners[race->numRunners]->health = health;
race->runners[race->numRunners]->dead = dead;
race->numRunners++;
return 1;
}
Caveat: Because there's so much missing [unwritten] code, this isn't a complete solution.
But, I notice at least two bugs: the isOver bugs in my top comments. And, incrementing race->numRunners in addDorc.
isOver also has the return 0; misplaced [inside the loop]. That should go as the last statement in the function. If you had compiled with -Wall [which you should always do], that should have been flagged by the compiler (e.g. control reaches end of non-void function)
From that, only one "dorc" would get created (for the first eligible runner). That may be what you want, but [AFAICT] you want to try to create more dorcs (one more for each valid runner).
Also, the bug the compiler flagged is because you're calling addDorc(race); but addDorc takes more arguments.
It's very difficult to follow the code when you're doing (e.g.) race->dorcs[race->numDorcs]->whatever everywhere.
Better to do (e.g.):
EntityType *ent = &race->dorcs[race->numDorcs];
ent->whatever = ...;
Further, it's likely that your thread functions would like a pointer to their [respective] control structs (vs. just passing " ").
Anyway, I've refactored your code to incorporate these changes. I've only tried to fix the obvious/glaring bugs from simple code inspection, but I've not tried to recompile or address the correctness of your logic.
So, there's still more work to do, but the simplifications may help a bit.
void
launch(void)
{
race = malloc(sizeof(RaceInfoType));
race->numRunners = 0;
initRunners(race);
if (sem_init(&race->mutex,0,1) < 0) {
printf("semaphore initialization error\n");
exit(1);
}
strcpy(race->winner," ");
srand((unsigned)time(NULL));
int i;
for (i = 0; i < race->numRunners; ++i) {
RunnerType *run = &race->runners[i];
EntityType *ent = &run->ent;
pthread_create(&ent->thr,NULL,goRunner,ent);
}
race->numDorcs = 0;
}
int
addDorc(RaceInfoType* race,char *avatar,int path,int currPos)
{
if (race->numDorcs == MAX_DORCS) {
printf("Error: Maximum dorcs already reached. \n");
return 0;
}
EntityType *ent = malloc(sizeof(*ent));
race->dorcs[race->numDorcs] = ent;
int timmysColumn = ent->currPos;
int haroldsColumn = ent->currPos;
int halfwayColumn = (timmysColumn + haroldsColumn) / 2;
int r = rand()%100;
#if 0
pthread_t dorc;
#endif
if (r <= 30) {
strcpy(ent->avatar,"d");
ent->currPos = 2;
if (r <= 33) {
ent->path = timmysColumn;
} else if (r <= 66) {
ent->path = haroldsColumn;
} else {
ent->path = halfwayColumn;
}
pthread_create(&ent->thr,NULL,goDorc,ent);
}
#if 0
race->numRunners++;
#else
race->numDorcs += 1;
#endif
}
int
isOver(RaceInfoType* race)
{
int i;
for (i = 0; i < race->numRunners; ++i) {
#if 0
if ((race->winner != " ") ||
(race->runners[race->numRunners]->dead = 1))
return 1;
#else
RunnerType *run = &race->runners[i];
if ((race->winner != " ") || (run->dead == 1))
return 1;
#endif
addDorc(race);
#if 0
return 0;
#endif
}
#if 1
return 0;
#endif
}
void
initRunners(RaceInfoType* r)
{
addRunner(r,"Timmy","T",10,35,50,0);
addRunner(r,"Harold","H",14,35,50,0);
}
int
addRunner(RaceInfoType* race,char *name,char *avatar,int path,int currPos,
int health,int dead)
{
if (race->numRunners == MAX_RUNNERS) {
printf("Error: Maximum runners already reached. \n");
return 0;
}
RunnerType *run = malloc(sizeof(*run));
race->runners[race->numRunners] = run;
strcpy(run->name,name);
EntityType *ent = &run->ent;
strcpy(ent->avatar,avatar);
ent->path = path;
ent->currPos = currPos;
run->health = health;
run->dead = dead;
race->numRunners++;
return 1;
}
UPDATE:
I noticed in addDorc(), you put pthread_t dorc; in an if statement. I don't quite understand what my if statement is actually supposed to be checking though.
I forgot to mention/explain. I wrapped your/old code and my/new code with preprocessor conditionals (e.g.):
#if 0
// old code
#else
// new code
#endif
After the cpp stage, the compiler will only see the // new code stuff. Doing this was an instructional tool to show [where possible] what code you had vs what I replaced it with. This was done to show the changes vs. just rewriting completely.
If we never defined NEVERWAS with a #define NEVERWAS, then the above block would be equivalent to:
#ifdef NEVERWAS
// old code ...
#else
// new code
#endif
Would it still be under the if(r <= 30) part like I did in my original code?
Yes, hopefully now, it is more clear. #if is a cpp directive to include/exclude code (as if you had edited that way). But, a "real" if is an actual executable statement that is evaluated at runtime [as it was before], so no change needed.
My other concern is it doesn't look like dorc is used anywhere in the function because you write pthread_create(&ent->thr,NULL,goDorc,ent); which seems to use ent instead?
That is correct. It is not used/defined and the value goes to ent->thr. As you had it, the pthread_t value set by pthread_create would be lost [when dorc goes out of scope]. So, unless it's saved somewhere semi-permanent (e.g. in ent->thr), there would be no way to do a pthread_join call later.
I am using bitwise operators to shift the binary value of shorts within a linked list. The function is recursive and after an arbitrary number of occurrences, my right shift seems to affect the value of a short in the next link despite me not pointing to this link at all at this point of the function. Here is my code :
static void move_right(t_tetri *piece) {
int i;
i = 0;
piece->x_offset++;
while (i < piece->height) {
piece->shape[i] = piece->shape[i] >> 1;
i++;
}
}
int ft_solve(t_map *map, t_tetri *list) {
if (list == NULL) return (1);
while (list->y_offset + list->height <= map->size) {
while (list->x_offset + list->width <= map->size) {
if (put_tetri(map, list)) {
set_piece(map, list);
if (ft_solve(map, list->next)) return (1);
else unset_piece(map, list);
}
move_right(list);
}
reset_piece(list);
}
list->y_offset = 0;
return (0);
}
piece->shape is an array containing 4 short but I'm mostly concerned about the first of these here. In certain cases (not all) when I go through the move_right function the value of piece->next->shape[0] is shifted in the same way, which poses a big problem for the next recursion of ft_solve.
Would anyone have any idea?
I can post more of my code if necessary, I'm not really used to ask questions here so if you need more information I'm ready to add it.
I'm just starting to learn C from Head First C, but I'm having difficulty understanding how refactor my code into multiple functions, more specifically, I don't know how to get functions to work and am confused how to take user input.
How would I incorporate a function like the one below into the main function? What are some other function examples I could use to refactor? Thank you so much!
void get_card_name(char *prompt, char *card_name)
Main function
int main()
{
char card_name[3];
int count = 0;
while ( card_name[0] != 'X' ) {
puts("Enter the card_name: ");
scanf("%2s", card_name);
int val = 0;
switch(card_name[0]) {
case 'K':
case 'Q':
case 'J':
val = 10;
break;
case 'A':
val = 11;
break;
case 'X':
continue;
default:
val = atoi(card_name);
if ((val < 1) || (val > 10)) {
puts("I dont understand that value!");
continue;
}
}
if ((val > 2) && (val < 7)) {
count++;
} else if (val == 10) {
count--;
}
printf("Current count: %i\n", count);
}
return 0;
}
The generic answer when it comes to refactoring is "If it looks complicated or hard to read, try to break it down into smaller pieces that are easier to read (and understand).".
In your case you have this:
int main() {
/* Initial state needed later on */
/* Do some complicated stuff */
}
To refactor this, you need to find out what parts of the initial state you need to keep close to whatever you are going to move away into its own function. In your example, card_name and count are both used inside the complicated bit, and nowhere else. So you can, and should, keep those close the complicated bits:
void do_card_stuff() {
char card_name[3];
int count = 0;
/* Do some complicated stuff */
}
int main() {
do_card_stuff();
}
And, lo and behold, you've refactored your code. If you still think that the card stuff looks complicated, try to break it up into more pieces:
int get_card_value(char card) {
/* Do some complicated stuff */
return value;
}
int do_card_stuff() {
char card_name[3];
int count = 0;
int value;
/* Loop */
/* Get card value from user */
value = get_card_value(card_name[0]);
}
int main() {
do_card_stuff();
}
Just keep at it until it's just silly to break it into smaller bits and you're done. Also, try to keep in mind that the code you break out should be as generic as possible since this will let you re-use this code later on (potentially in other projects).
HI.. I want an example of how to implement FSM using function pointers in C.
See this simple example on how to implement a finite state machine in C.
An example is too big to write as an answer here.
Here's an existing example, which I found by Googling for state machine c "function pointer": Implementing Efficient State Machines
Here is a little demo of using function pointers in ARDUINO. This example does not allow for concurrency. It perfectly transferable to normal C if make write the setup and loop inside main()
Each state is a void() function. Each state function is responsible for reading input and setting output. When this is done the function should return immediately. It will be called again directly. The function is also responsible for state-transition by calling the leave function immediately before returning. Each state function should have a static long variable for timekeeping.
A global variable state is set to point to the initial state in the setup routine.
I wanted timekeeping in the different states so i implemented the state transitions by 2 functions:
void enter(long *stateTime), this should be called the very first thing when entering the state functions. It activates the state if inactive end keeps time.
void leave(void (*next)(), long *statetime), this changes the global state pointer and deactivates the current state.
void (*state)();//function pointer for state machine
long prevMillis = 0;//timekeeper
const int LEDPIN = 13;
int counter1 = 0;
void enter(long *statetime){
if(*statetime==-1){//check for passive state
prevMillis = millis();//set timemark when entering state
}//if(statetime==0)
*statetime = millis()-prevMillis;//keep time
}//enter()
void leave(void (*next)(), long *statetime){
*statetime=-1;//set state to passive
state=next;//point to next state
}//leave()
void off500ms(){
static long stateMillis;//timer for this state
enter(&stateMillis);//update timer
digitalWrite(LEDPIN, LOW);
if(stateMillis>499){//check if time is up
leave(on500ms, &stateMillis);
}//if(stateMillis>499)
}//off500ms()
void off2s(){
static long stateMillis;//timer for this state
enter(&stateMillis);//update timer
digitalWrite(LEDPIN, LOW);
if(stateMillis>1999){//check if time is up
leave(on500ms, &stateMillis);
}//if(stateMillis>499)
}//off2s()
void on500ms(){
static long stateMillis;//timer for this state
enter(&stateMillis);//update timer
digitalWrite(LEDPIN, HIGH);
if(stateMillis >499){//time is up
if(++counter1==6){//number of blinks
leave(off2s, &stateMillis);
counter1=0;//reset counter
}else{//if(++counter1==6)
leave(off500ms, &stateMillis);
}//if(++counter1==6)
}//if(stateMills>499)
}//on500ms
void setup(){
pinMode(LEDPIN, OUTPUT);
state = on500ms;//set initial state
}/setup()
void loop(){
state();//start FSM
}//loop
I would say initialize a array of pointers to event handlers. So each element of a array is a function pointer to a particular event which is part of an enum.
if foo is your array of function pointers which is initialized to event then call foo[event]() when any event occurs.
Try coding for calling a function pointer first, next you can move to array and come back to SO if there are more doubts.
For a start you can read about function pointers here.
State transtion code can be utilize either by array or switch case. Written under if else directive.
#include <stdio.h>
#include <stdlib.h>
int entry_state(void);
int foo_state(void);
int bar_state(void);
int exit_state(void);
enum state_codes lookup_transitions(enum state_codes, enum ret_codes);
/* array and enum below must be in sync! */
int (* state[])(void) = { entry_state, foo_state, bar_state, exit_state};
enum state_codes { entry, foo, bar, end};
enum ret_codes { ok, fail, repeat};
struct transition {
enum state_codes src_state;
enum ret_codes ret_code;
enum state_codes dst_state;
};
/* transitions from end state aren't needed */
struct transition state_transitions[] = {
{entry, ok, foo},
{entry, fail, end},
{foo, ok, bar},
{foo, fail, end},
{foo, repeat, foo},
{bar, ok, end},
{bar, fail, end},
{bar, repeat, foo}};
int main(int argc, char *argv[]) {
enum state_codes cur_state = entry;
enum ret_codes rc;
int (* state_fun)(void);
for (;;) {
state_fun = state[cur_state];
rc = state_fun();
if (end == cur_state)
break;
cur_state = lookup_transitions(cur_state, rc);
}
return EXIT_SUCCESS;
}
/*
* lookup_transition() function has time complexity of class O(n).
* We can optimize it.
* */
enum state_codes
lookup_transitions(enum state_codes cur_state, enum ret_codes rc)
{
#if 0
switch (cur_state) {
case entry:
cur_state = ((rc == ok) ? (foo) : (end));
break;
case foo:
cur_state = ((rc == ok) ? (bar) : ((rc == fail) ? (end) : (foo)));
break;
default:
cur_state = ((rc == ok) ? (end) : ((rc == fail) ? (end) : (foo)));
break;
}
return cur_state;
#else
char arr_size = (sizeof(state_transitions) / sizeof(state_transitions[0])); /* This can be shifted to main function to avoid redundant job. */
char count;
for (count = 0; count < arr_size; count++) {
if ((state_transitions[count].src_state == cur_state) && (state_transitions[count].ret_code == rc)) {
return (state_transitions[count].dst_state);
}
}
#endif
}
int entry_state(void)
{
int st;
enum ret_codes rc;
printf("YOU ARE IN ENTRY STATE.\nEnter 0/1: ");
scanf("%d", &st);
rc = ((st == 1) ? (fail) : (ok));
return rc;
}
int foo_state(void)
{
int st;
enum ret_codes rc;
printf("YOU ARE IN FOO STATE.\nEnter 0/1/2: ");
scanf("%d", &st);
rc = ((st == 0) ? (ok) : ((st == 2) ? (repeat) : (fail)));
return rc;
}
int bar_state(void)
{
int st;
enum ret_codes rc;
printf("YOU ARE IN BAR STATE.\nEnter 0/1/2: ");
scanf("%d", &st);
rc = ((st == 0) ? (ok) : ((st == 2) ? (repeat) : (fail)));
return rc;
}
int exit_state(void)
{
printf("YOU ARE IN EXIT STATE.\n");
exit(EXIT_SUCCESS);
}