Unexpected Value Output When Not Using Visual Studio - c

Question

I've been working on a program for my Algorithm Analysis class where I have to solve the Knapsack problem with Brute Force, greedy, dynamic, and branch and bound strategies. Everything works perfectly when I run it in Visual Studio 2012, but if I compile with gcc and run it on the command line, I get a different result:
Visual Studio:
+-------------------------------------------------------------------------------+
| Number of | Processing time in seconds / Maximum benefit value |
| +---------------+---------------+---------------+---------------+
| items | Brute force | Greedy | D.P. | B. & B. |
+---------------+---------------+---------------+---------------+---------------+
| 10 + 0 / 1290 + 0 / 1328 + 0 / 1290 + 0 / 1290 |
+---------------+---------------+---------------+---------------+---------------+
| 20 + 0 / 3286 + 0 / 3295 + 0 / 3200 + 0 / 3286 |
+---------------+---------------+---------------+---------------+---------------+
cmd:
+-------------------------------------------------------------------------------+
| Number of | Processing time in seconds / Maximum benefit value |
| +---------------+---------------+---------------+---------------+
| items | Brute force | Greedy | D.P. | B. & B. |
+---------------+---------------+---------------+---------------+---------------+
| 10 + 0 / 1290 + 0 / 1328 + 0 / 1599229779+ 0 / 1290 |
+---------------+---------------+---------------+---------------+---------------+
| 20 + 0 / 3286 + 0 / 3295 + 0 / 3200 + 0 / 3286 |
+---------------+---------------+---------------+---------------+---------------+
The same number always shows up, "1599229779." Notice that the output is only messed up the first time the Dynamic algorithm is run.
Here is my code:
typedef struct{
short value; //This is the value of the item
short weight; //This is the weight of the item
float ratio; //This is the ratio of value/weight
} itemType;
typedef struct{
time_t startingTime;
time_t endingTime;
int maxValue;
} result;
result solveWithDynamic(itemType items[], int itemsLength, int maxCapacity){
result answer;
int rowSize = 2;
int colSize = maxCapacity + 1;
int i, j; //used in loops
int otherColumn, thisColumn;
answer.startingTime = time(NULL);
int **table = (int**)malloc((sizeof *table) * rowSize);//[2][(MAX_ITEMS*WEIGHT_MULTIPLIER)];
for(i = 0; i < rowSize; i ++)
table[i] = (int*)malloc((sizeof *table[i]) * colSize);
table[0][0] = 0;
table[1][0] = 0;
for(i = 1; i < maxCapacity; i++) table[1][i] = 0;
for(i = 0; i < itemsLength; i++){
thisColumn = i%2;
otherColumn = (i+1)%2; //this is always the other column
for(j = 1; j < maxCapacity + 1; j++){
if(items[i].weight <= j){
if(items[i].value + table[otherColumn][j-items[i].weight] > table[otherColumn][j])
table[thisColumn][j] = items[i].value + table[otherColumn][j-items[i].weight];
else
table[thisColumn][j] = table[otherColumn][j];
} else {
table[thisColumn][j] = table[thisColumn][j-1];
}//end if/else
}//end for
}//end for
answer.maxValue = table[thisColumn][maxCapacity];
answer.endingTime = time(NULL);
for(i = 0; i < rowSize; i ++)
free(table[i]);
free(table);
return answer;
}//end solveWithDynamic
Just a bit of explanation. I was having trouble with the memory consumption of this algorithm because I have to run it for a set of 10,000 items. I realized that I didn't need to store the whole table, because I only ever looked at the previous column. I actually figured out that you only need to store the current row and x+1 additional values, where x is the weight of the current itemType. It brought the memory required from (itemsLength+1) * (maxCapacity+1) elements to 2*(maxCapacity+1) and possibly (maxCapacity+1) + (x+1) (although I don't need to optimize it that much).
Also, I used printf("%d", answer.maxValue); in this function, and it still came out as "1599229779." Can anyone help me figure out what is going on? Thanks.

Answer 1

Can't be sure that that is what causes it, but
for(i = 1; i < maxCapacity; i++) table[1][i] = 0;
you leave table[1][maxCapacity] uninitialised, but then potentially use it:
for(j = 1; j < maxCapacity + 1; j++){
if(items[i].weight <= j){
if(items[i].value + table[otherColumn][j-items[i].weight] > table[otherColumn][j])
table[thisColumn][j] = items[i].value + table[otherColumn][j-items[i].weight];
else
table[thisColumn][j] = table[otherColumn][j];
} else {
table[thisColumn][j] = table[thisColumn][j-1];
}//end if/else
}//end for
If that is always zero with Visual Studio, but nonzero with gcc, that could explain the difference.