Matrix Values change after function is executed
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I am using C++ to create an algorithm to amend matrix entries - however I have come across some strange behaviour.
The algorithm itself should provide two matrices, one of which is inputted as a variable and should be amended in the algorithm, and the other will be returned.
All was fine until I noticed that the matrix that was inputted has entry values inside the function that differ from outside the function (after the function had been executed).
I will not write out the whole code (because it is rather long and I don't think is relevant), however, I will show snippet, hopefully elucidating the issue.
double** function(double** A)
{
/*Some coding that amends entries in A...*/
for (int i = 0; i <= Dimension - 1; i++)
{
for (int j = 0; j <= Dimension -1; j++)
{
std::cout << A[i][j] << " ";
}
std::cout << "n";
}
return B; /*nothing else after this line*/
}
This is the function (above) used which currently outputs the correct values of matrix A. However, when ouputting the values of A in the main() function, i.e.
int main()
{
/*some code*/
B = function(A)
for (int i = 0; i <= Dimension - 1; i++)
{
for (int j = 0; j <= Dimension -1; j++)
{
std::cout << A[i][j] << " ";
}
std::cout << "n";
}
}
The values seem to differ from the ones displayed inside the function. The values are not random, they seem to be fixed values every time I compile the code, so I don't believe its a memory issue.
I would appreciate some guidance on this issue, if possible - I don't think is related to the coding of my algorithm, hence why I have not included it - If you think otherwise, please let me know. Thank you.
c++ arrays pointers matrix multidimensional-array
asked Nov 20 at 0:21
Naji
1
add a comment |
up vote
0
down vote
favorite
I am using C++ to create an algorithm to amend matrix entries - however I have come across some strange behaviour.
The algorithm itself should provide two matrices, one of which is inputted as a variable and should be amended in the algorithm, and the other will be returned.
All was fine until I noticed that the matrix that was inputted has entry values inside the function that differ from outside the function (after the function had been executed).
I will not write out the whole code (because it is rather long and I don't think is relevant), however, I will show snippet, hopefully elucidating the issue.
double** function(double** A)
{
/*Some coding that amends entries in A...*/
for (int i = 0; i <= Dimension - 1; i++)
{
for (int j = 0; j <= Dimension -1; j++)
{
std::cout << A[i][j] << " ";
}
std::cout << "n";
}
return B; /*nothing else after this line*/
}
This is the function (above) used which currently outputs the correct values of matrix A. However, when ouputting the values of A in the main() function, i.e.
int main()
{
/*some code*/
B = function(A)
for (int i = 0; i <= Dimension - 1; i++)
{
for (int j = 0; j <= Dimension -1; j++)
{
std::cout << A[i][j] << " ";
}
std::cout << "n";
}
}
The values seem to differ from the ones displayed inside the function. The values are not random, they seem to be fixed values every time I compile the code, so I don't believe its a memory issue.
I would appreciate some guidance on this issue, if possible - I don't think is related to the coding of my algorithm, hence why I have not included it - If you think otherwise, please let me know. Thank you.
c++ arrays pointers matrix multidimensional-array
asked Nov 20 at 0:21
Naji
1
3
All you've supplied is code that outputs values from the matrix. Nothing about how it's declared, initialized, or modified. Half the variables you're using don't exist in the code you've provided. Minimal is good, but something that reproduces the problem does need to be provided.
– zzxyz
Nov 20 at 0:26
3
Unrelated:for (int i = 0; i <= Dimension - 1; i++)Makes people look at you funny even if the compiler doesn't and quietly modifies the output to eliminate the waste. Preferfor (int i = 0; i < Dimension; i++).
– user4581301
Nov 20 at 0:35
add a comment |
up vote
0
down vote
favorite
up vote
0
down vote
favorite
I am using C++ to create an algorithm to amend matrix entries - however I have come across some strange behaviour.
The algorithm itself should provide two matrices, one of which is inputted as a variable and should be amended in the algorithm, and the other will be returned.
All was fine until I noticed that the matrix that was inputted has entry values inside the function that differ from outside the function (after the function had been executed).
I will not write out the whole code (because it is rather long and I don't think is relevant), however, I will show snippet, hopefully elucidating the issue.
double** function(double** A)
{
/*Some coding that amends entries in A...*/
for (int i = 0; i <= Dimension - 1; i++)
{
for (int j = 0; j <= Dimension -1; j++)
{
std::cout << A[i][j] << " ";
}
std::cout << "n";
}
return B; /*nothing else after this line*/
}
This is the function (above) used which currently outputs the correct values of matrix A. However, when ouputting the values of A in the main() function, i.e.
int main()
{
/*some code*/
B = function(A)
for (int i = 0; i <= Dimension - 1; i++)
{
for (int j = 0; j <= Dimension -1; j++)
{
std::cout << A[i][j] << " ";
}
std::cout << "n";
}
}
The values seem to differ from the ones displayed inside the function. The values are not random, they seem to be fixed values every time I compile the code, so I don't believe its a memory issue.
I would appreciate some guidance on this issue, if possible - I don't think is related to the coding of my algorithm, hence why I have not included it - If you think otherwise, please let me know. Thank you.
c++ arrays pointers matrix multidimensional-array
asked Nov 20 at 0:21
Naji
1
I am using C++ to create an algorithm to amend matrix entries - however I have come across some strange behaviour.
The algorithm itself should provide two matrices, one of which is inputted as a variable and should be amended in the algorithm, and the other will be returned.
All was fine until I noticed that the matrix that was inputted has entry values inside the function that differ from outside the function (after the function had been executed).
I will not write out the whole code (because it is rather long and I don't think is relevant), however, I will show snippet, hopefully elucidating the issue.
double** function(double** A)
{
/*Some coding that amends entries in A...*/
for (int i = 0; i <= Dimension - 1; i++)
{
for (int j = 0; j <= Dimension -1; j++)
{
std::cout << A[i][j] << " ";
}
std::cout << "n";
}
return B; /*nothing else after this line*/
}
This is the function (above) used which currently outputs the correct values of matrix A. However, when ouputting the values of A in the main() function, i.e.
int main()
{
/*some code*/
B = function(A)
for (int i = 0; i <= Dimension - 1; i++)
{
for (int j = 0; j <= Dimension -1; j++)
{
std::cout << A[i][j] << " ";
}
std::cout << "n";
}
}
The values seem to differ from the ones displayed inside the function. The values are not random, they seem to be fixed values every time I compile the code, so I don't believe its a memory issue.
I would appreciate some guidance on this issue, if possible - I don't think is related to the coding of my algorithm, hence why I have not included it - If you think otherwise, please let me know. Thank you.
c++ arrays pointers matrix multidimensional-array
c++ arrays pointers matrix multidimensional-array
asked Nov 20 at 0:21
Naji
1
asked Nov 20 at 0:21
Naji
1
asked Nov 20 at 0:21
Naji
1
asked Nov 20 at 0:21
Naji
1
asked Nov 20 at 0:21
Naji
1
1
3
All you've supplied is code that outputs values from the matrix. Nothing about how it's declared, initialized, or modified. Half the variables you're using don't exist in the code you've provided. Minimal is good, but something that reproduces the problem does need to be provided.
– zzxyz
Nov 20 at 0:26
3
Unrelated:for (int i = 0; i <= Dimension - 1; i++)Makes people look at you funny even if the compiler doesn't and quietly modifies the output to eliminate the waste. Preferfor (int i = 0; i < Dimension; i++).
– user4581301
Nov 20 at 0:35
add a comment |
3
All you've supplied is code that outputs values from the matrix. Nothing about how it's declared, initialized, or modified. Half the variables you're using don't exist in the code you've provided. Minimal is good, but something that reproduces the problem does need to be provided.
– zzxyz
Nov 20 at 0:26
3
Unrelated:for (int i = 0; i <= Dimension - 1; i++)Makes people look at you funny even if the compiler doesn't and quietly modifies the output to eliminate the waste. Preferfor (int i = 0; i < Dimension; i++).
– user4581301
Nov 20 at 0:35
3
3
All you've supplied is code that outputs values from the matrix. Nothing about how it's declared, initialized, or modified. Half the variables you're using don't exist in the code you've provided. Minimal is good, but something that reproduces the problem does need to be provided.
– zzxyz
Nov 20 at 0:26
All you've supplied is code that outputs values from the matrix. Nothing about how it's declared, initialized, or modified. Half the variables you're using don't exist in the code you've provided. Minimal is good, but something that reproduces the problem does need to be provided.
– zzxyz
Nov 20 at 0:26
3
3
Unrelated:
for (int i = 0; i <= Dimension - 1; i++) Makes people look at you funny even if the compiler doesn't and quietly modifies the output to eliminate the waste. Prefer for (int i = 0; i < Dimension; i++).– user4581301
Nov 20 at 0:35
Unrelated:
for (int i = 0; i <= Dimension - 1; i++) Makes people look at you funny even if the compiler doesn't and quietly modifies the output to eliminate the waste. Prefer for (int i = 0; i < Dimension; i++).– user4581301
Nov 20 at 0:35
add a comment |
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3
All you've supplied is code that outputs values from the matrix. Nothing about how it's declared, initialized, or modified. Half the variables you're using don't exist in the code you've provided. Minimal is good, but something that reproduces the problem does need to be provided.
– zzxyz
Nov 20 at 0:26
3
Unrelated:
for (int i = 0; i <= Dimension - 1; i++)Makes people look at you funny even if the compiler doesn't and quietly modifies the output to eliminate the waste. Preferfor (int i = 0; i < Dimension; i++).– user4581301
Nov 20 at 0:35