Convert a C++ code to Java

Programming Questions

jarain78

in Programming Questions • 10 months ago

Hi , I have a question,

I have a C++ code, how I do to convert it to java code?

typedef struct {
int y;
int x;
} loc_t;
typedef struct {
double Q[MAX_ACTIONS];
double sumQ;
double maxQ;
} stateAction_t;
const loc_t dir[MAX_ACTIONS]={
{ -1, 0}, /* N */
{ -1, 1}, /* NE */
{ 0, 1}, /* E */
{ 1, 1}, /* SE */
{ 1, 0}, /* S */
{ 1, -1}, /* SW */
{ 0, -1}, /* W */
{ -1, -1} /* NW */
};
// Map
int grid[Y_MAX][X_MAX]={
{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 },
{ -1, 1, 1, 1, 1, -1, 1, 1, 1, -1 },
{ -1, 1, 1, -1, 1, -1, 1, -1, 1, -1 },
{ -1, 1, 1, -1, 1, -1, 1, -1, 1, -1 },
{ -1, 1, 1, -1, 1, -1, 1, -1, 1, -1 },
{ -1, 1, 1, -1, 1, -1, 1, -1, 1, -1 },
{ -1, 1, 1, -1, 1, -1, 1, -1, 1, -1 },
{ -1, 1, 1, -1, 1, -1, 1, -1, 1, -1 },
{ -1, -1, 1, -1, 1, 1, 1, -1, 99, -1 },
{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 }
};
loc_t start={1, 1};

loc_t end={8, 8};

I´d tray to programing in java but it give some errors as you can see next:

illegal initializer for IA_Bot.loc_t

illegal initializer for <none>

this is the peace of the code with errors.

static int loc_t dir[] = {
{ -1, 0}, /* N */
{ -1, 1}, /* NE */
{ 0, 1}, /* E */
{ 1, 1}, /* SE */
{ 1, 0}, /* S */
{ 1, -1}, /* SW */
{ 0, -1}, /* W */
{ -1, -1} /* NW */
};
loc_t start={1, 1};
loc_t end={3, 8};

I would thank for the help

Replies(9)

timpulver

Re: Convert a C++ code to Java

10 months ago

Java / Processing does not know loc_t, use a PVector for this.

PVector[] dir = new PVector[]{
new PVector(-1, 0), /* N */
new PVector(-1, 1), /* NE */
new PVector(0, 1), /* E */
new PVector(1, 1), /* SE */
new PVector(1, 0), /* S */
new PVector(1, -1), /* SW */
new PVector(0, -1), /* W */
new PVector(-1, -1) /* NW */
};
PVector start = new PVector(1, 1);
PVector end = new PVector(3, 8);

PhiLho

Re: Convert a C++ code to Java

10 months ago

Or if you want to keep the int variables, and see how your structure is translated to Java, use:

class Loc
{
int x;
int y;
Loc(int _x, int _y) // So called constructor
{
x = _x;
y = _y;
}
String toString() // Optional but useful and standard in Java
{
return "Loc(" + x + ", " + y + ")";
}
}

Which you initialize as shown above: just replace PVector by Loc.

jarain78

Re: Convert a C++ code to Java

10 months ago

hello, thanks for the answer, solved my problem, but now I have this.

I have the following class:

Copy code

public class stateAction_t{
public double Q[] = new double[MAX_ACTIONS];
public double sumQ;
public double maxQ;
}

then one Statespace think as follows:

Copy code

int X_MAX = 10;
int Y_MAX = 10;
stateAction_t stateSpace[][] = new stateAction_t[Y_MAX][X_MAX];

but when I run my program, I generate an initialization error on the next line:

Copy code

public void initStateSpace(){
int x_state = 0;
int y_state = 0;
int action = 0;
for ( y_state = 1 ; y_state < Y_MAX ; y_state++ ) {
for ( x_state = 1 ; x_state < X_MAX ; x_state++ ) {
for (action = 1 ; action < MAX_ACTIONS ; action++) {
stateSpace[y_state][x_state].Q[action] = 0;
}
stateSpace[y_state][x_state].sumQ = 0;
stateSpace[y_state][x_state].maxQ = 0;
}
}
}

Many thanks to all for the help provided.

GoToLoop

Re: Convert a C++ code to Java

10 months ago

Even @ your original C code, you don't show us any example where struct stateAction_t is used anywhere!
Neither the value of constant MAX_ACTIONS !

In Java, when an array of a class is created, each individual element of it has to be instantiated as well.

for (action = 1 ; action < MAX_ACTIONS ; action++) {
  stateSpace[y_state][x_state] = new stateAction_t();
  stateSpace[y_state][x_state].Q[action] = 0;
}

Although I believe array Q has all its elements = 0 anyways!

PhiLho

Re: Convert a C++ code to Java

10 months ago

First, your function isn't useful the first time you create the classes: arrays are initialized at zero by default. It can be useful if you need to reset the arrays, though.
Second, your loops are strange, as you start at 1 instead of 0. Perhaps it is on purpose, but some beginners overlook the fact array indexes start at 0.
Last, I don't know what " an initialization error" is...
You should paste the exact error message you have, and point out which line has the problem.

GoToLoop

Re: Re: Convert a C++ code to Java

10 months ago

Just an addendum, for non-local variables:

Numerical primitives are initialized w/ 0.
Boolean w/ false.
Objects w/ null.

* [Edited]

PhiLho

Re: Convert a C++ code to Java

10 months ago

Strings are objects, and are initialized with null too...
You can add that booleans are initialized with false.

GoToLoop

Re: Re: Convert a C++ code to Java

10 months ago

Argh! Forgotten about boolean.
My bad, String is initialized w/ null as well.
I guess I got confused w/ Python or Lua about it, or something similar like BASIC.

jarain78

Re: Convert a C++ code to Java

10 months ago

hello, thanks for the help they gave me the program works very well, here I leave the program compelto, which helped me to solve.

is a program for reinforcement learning .

// Var tipo Int
static int X_MAX = 10;
static int Y_MAX = 10;
static int MAX_ACTIONS = 8;
static int GREEDY = 0; /* Choose best Q */
static int P_GREEDY = 1; /* Probabilistically choose best Q */
// static int x1 = 0;
// static int y1 = 0;
// Var tipo long
static long MAX_EPOCHS = 100000L;
// Var tipo double
static float EXPLORE_RATE = 0.2;
static float LEARNING_RATE = 0.6; /* Q-Learning Beta */
static float DISCOUNT_RATE = 0.5; /* Q-Learning Lambda */
static float RAND_MAX = 20;
public class loc_t {
public int x;
public int y;
loc_t(int _x, int _y) {
x = _x;
y = _y;
}
}
public class stateAction_t {
public double Q[] = new double[MAX_ACTIONS];
public double sumQ;
public double maxQ;
/*stateAction_t(double _Q[], double _sumQ, double _maxQ) {
Q = _Q;
sumQ = _sumQ;
maxQ = _maxQ;
}*/
}
loc_t[] dir = new loc_t[] {
new loc_t(-1, 0), /* N */
new loc_t(-1, 1), /* NE */
new loc_t(0, 1), /* E */
new loc_t(1, 1), /* SE */
new loc_t(1, 0), /* S */
new loc_t(1, -1), /* SW */
new loc_t(0, -1), /* W */
new loc_t(-1, -1) /* NW */
};
static int grid[][]= {
{-1, -1, -1, -1, -1, -1, -1, -1, -1, -1},
{-1, 1, 1, 1, 1, 1, 1, -1, 1, -1},
{-1, 1, 1, 1, 1, 1, 1, -1, 1, -1},
{-1, 1, 1, 1, 1, 1, 1, -1, 99, -1},
{-1, 1, 1, 1, 1, 1, 1, -1, 1, -1},
{-1, 1, 1, 1, 1, 1, 1, -1, 1, -1},
{-1, 1, 1, 1, 1, 1, 1, -1, 1, -1},
{-1, 1, 1, 1, 1, 1, 1, -1, 1, -1},
{-1, 1, 1, 1, 1, 1, 1, 1, 1, -1},
{-1, -1, -1, -1, -1, -1, -1, -1, -1, -1}
};
stateAction_t stateSpace[][] = new stateAction_t[Y_MAX][X_MAX];
loc_t start = new loc_t(1, 1);
loc_t end = new loc_t(8, 3);
double explore = EXPLORE_RATE;
int actionSelection = P_GREEDY;
void setup() {
println("Iniciando...");
long epochs = 0;
int action = 0;
int x1 = 0;
int y1 = 0;
x1 = start.x;
y1 = start.y;
initStateSpace();
println("Salio de la Inicializacion");
for ( epochs = 0 ; epochs < MAX_EPOCHS ; epochs++ ) {
action = chooseAction( y1, x1 );
updateFunction( y1, x1, action );
x1 += dir[action].x;
y1 += dir[action].y;
if ((x1 == end.x) && (y1 == end.y)) {
x1 = start.x;
y1 = start.y;
}
}
showPath();
println("Termino...");
}
void draw() {
}
public float getRand(float x) {
float A = 0.0;
A = random(RAND_MAX);
float A1 = x*(A/(RAND_MAX+1.0));
return A1;
}
public double getSRand() {
float B = 0.0;
B = random(RAND_MAX)/(RAND_MAX);
return B;
}
public void initStateSpace() {
int x_state = 0;
int y_state = 0;
int action = 0;
for ( y_state = 0 ; y_state < Y_MAX ; y_state++ ) {
for ( x_state = 0 ; x_state < X_MAX ; x_state++ ) {
for (action = 0 ; action < MAX_ACTIONS ; action++) {
stateSpace[y_state][x_state] = new stateAction_t();
stateSpace[y_state][x_state].Q[action] = 0.0;
}
stateSpace[y_state][x_state].sumQ = 0.0;
stateSpace[y_state][x_state].maxQ = 0.0;
}
}
return;
}// End
public void findMaxQ( int y, int x ) {
int i = 0;
stateSpace[y][x].maxQ = 0.0;
for (i = 0 ; i < MAX_ACTIONS ; i++) {
if (stateSpace[y][x].Q[i] > stateSpace[y][x].maxQ) {
stateSpace[y][x].maxQ = stateSpace[y][x].Q[i];
}
}
return;
}// End
public void updateSum( int y, int x ) {
int i = 0;
stateSpace[y][x].sumQ = 0.0;
for (i = 0 ; i < MAX_ACTIONS ; i++) {
stateSpace[y][x].sumQ += stateSpace[y][x].Q[i];
}
return;
} // End
public boolean legalMove( int y_state, int x_state, int action ) {
int y = y_state + dir[action].y;
int x = x_state + dir[action].x;
if (grid[y][x] < 0) return false;
else return true;
}// End
public int getRandomAction( int y, int x ) {
int action = 0;
do {
action = (int) getRand( MAX_ACTIONS );
}
while (!legalMove (y, x, action));
return action;
}// End
public int chooseAction( int y, int x ) {
int action = 0;
int count = 0;
if (actionSelection == GREEDY) {
findMaxQ(y, x);
for (action = 0 ; action < MAX_ACTIONS ; action++) {
if (stateSpace[y][x].maxQ == stateSpace[y][x].Q[action]) {
if (legalMove(y, x, action)) return(action);
}
}
}
else if (actionSelection == P_GREEDY) {
if ((EXPLORE_RATE > getSRand()) || (stateSpace[y][x].sumQ == 0.0)) {
/* Explore! */
action = getRandomAction(y, x);
}
else {
double prob;
/* Exploit! */
action = getRandomAction(y, x);
for (count = 0 ; count < MAX_ACTIONS ; count++) {
prob = (stateSpace[y][x].Q[action] / stateSpace[y][x].sumQ);
if (legalMove(y, x, action)) {
if (prob > getSRand()) {
return(action);
}
}
if (++action == MAX_ACTIONS) action = 0;
}
/* Went through the possible actions, but did not pick one. At
* this point, we'll just pick one randomly.
*/
if (count == MAX_ACTIONS) {
action = getRandomAction(y, x);
}
}
}
else {
//sassert(0);
}
return action;
}// End
public void updateFunction( int y, int x, int action ) {
int newy = y + dir[action].y;
int newx = x + dir[action].x;
double reward;
reward = (double)grid[newy][newx] + 0.1;
/* Update the maxQ value for the state */
findMaxQ( newy, newx );
/* Q_Learning */
stateSpace[y][x].Q[action] += LEARNING_RATE * (reward + (DISCOUNT_RATE * stateSpace[newy][newx].maxQ) - stateSpace[y][x].Q[action]);
/* Update the payoff sum */
updateSum( y, x );
return;
}// End
public void showPath() {
int x, y, action;
actionSelection = GREEDY;
x = start.x;
y = start.y;
print("\n");
for ( y = 0 ; y < Y_MAX ; y++ ) {
for ( x = 0 ; x < X_MAX ; x++ ) {
print(grid[y][x]);
print(" ");
}
print("\n");
}
print("\n");
x = start.x;
y = start.y;
while (true) {
grid[y][x] = 0;
if ((x == end.x) && (y == end.y)) break;
action = chooseAction( y, x );
x += dir[action].x;
y += dir[action].y;
}
print("\n");
for ( y = 0 ; y < Y_MAX ; y++ ) {
for ( x = 0 ; x < X_MAX ; x++ ) {
print(grid[y][x]);
print(" ");
}
print("\n");
}
print("\n");
return;
}// End

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