Re: how to delete arrays to save memery space c++ - C / C++ / MFC Discussion Boards

Re: how to delete arrays to save memery space c++

Rajesh R Subramanian3-May-10 8:50

3-May-10 8:50

I already provided you a link. Click on each container class there and the page would contain an example at the bottom. You might want to search Google for more examples and tutorials.

“Follow your bliss.” – Joseph Campbell

Re: how to delete arrays to save memery space c++

CPallini3-May-10 8:18

CPallini

3-May-10 8:18

mrby123 wrote:
Should I put a loop of 1000 to delete ?

Yes.

mrby123 wrote:
I am not sure how to put code with a loop to delete.

As Nemanja suggested, you should call delete on every pointer that was assigned by means of new.
Smile | :)

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Re: how to delete arrays to save memery space c++

mrby1233-May-10 8:35

mrby123

3-May-10 8:35

Should I put:

for (i=0;i<1000;i++)
{
delete tim_var[i];
}

or for (i=0;i<1000;i++)
{
delete *tim_var[i];
}

Please comment.

Thanks

Re: how to delete arrays to save memery space c++

Rajesh R Subramanian3-May-10 8:52

Rajesh R Subramanian

3-May-10 8:52

mrby123 wrote:
delete tim_var[i];

mrby123 wrote:
delete *tim_var[i];

Please try to understand the difference between the two. That'll help you do it on your own. Come up and ask if you have more doubts in the understanding process.

People here are helpful. But they try not to hand code to you in a plate, for your own benefit. Smile | :)

“Follow your bliss.” – Joseph Campbell

Re: how to delete arrays to save memery space c++

mrby1233-May-10 9:07

mrby123

3-May-10 9:07

Thanks. In fact,

delete *tim_var[i];

can not be compiled, but

delete tim_var[i];

I think the latter delete a two dimensional array declared and initialized by:

float* tim_var[1000];
for (i=0;i<1000;i++)
{
tim_var[i]=new float[6];
}

for(i=0;i<1000;i++) {
for(int j=0;j<6;j++)
{
tim_var[i][j]=0;
}
}

Re: how to delete arrays to save memery space c++

CPallini3-May-10 9:00

CPallini

3-May-10 9:00

consider

int * p;
p = new int[5];

the pointer assigned is p, hence you have to call

delete p;

in order to release memory.
Now try with your actual code.
Smile | :)

Re: how to delete arrays to save memery space c++

mrby1233-May-10 9:21

mrby123

3-May-10 9:21

Thanks CPallini.

Your above code works for one-dimensional array p[5].

But now I got tim_var[1000][6]

Re: how to delete arrays to save memery space c++

David Crow3-May-10 9:30

David Crow

3-May-10 9:30

mrby123 wrote:
But now I got tim_var[1000][6]

Have you tried:

float **tim_var;
  
tim_var = new float*[1000]; <<----------
                                       |
for (int x = 0; x < 1000; x++)         |
{                                      |
    tim_var[x] = new float[6]; <<----- |
                                     | | 
    for (int y = 0; y < 6; y++)      | |
        tim_var[x][y] = 0.0;         | |
}                                    | |
                                     | |
for (x = 0; x < 1000; x++)           | |
    delete [] tim_var[x]; <<---------- |
                                       |
delete [] tim_var; <<-------------------

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Re: how to delete arrays to save memery space c++

mrby1233-May-10 9:54

mrby123

3-May-10 9:54

Thanks. Your code compiled OK.

Want do you think. I think it will work ?

Thanks

Re: how to delete arrays to save memery space c++

mrby1234-May-10 10:37

mrby123

4-May-10 10:37

My intention is to release all memories. The following code was suggested by you. I tried however, seems a problem. I got error message when I run the program: (delete statements got problem). It compiles OK.

"DAMAGE after normal block (#125) at 0x00E40610"

Would you please check ?

Re: how to delete arrays to save memery space c++

David Crow5-May-10 2:40

David Crow

5-May-10 2:40

mrby123 wrote:
Would you please check ?

Check what? The code snippet I provided you here is fine. If you have added to it or taken from it, that would be the reason for the error.

Re: how to delete arrays to save memery space c++

mrby1235-May-10 10:37

mrby123

5-May-10 10:37

Thanks. I believe your code is good. I got the problem that is how to declare, define, and call a function passing two dimensional array.

Please correct me. I am trying to delcare, define, and call a two dimensional array like:

declare in the header file:
void CCvib_procDlg::time(float*);

Define:
void CCvib_procDlg::time(float delms[][6])
{ ... code ... }

call:
time(&delms[0][0]);

When I tried to compile, I got:
error C2511: 'time' : overloaded member function 'void (float [][6])' not found in 'CC_vib_procDlg'

Please correct mm. Thanks

Re: how to delete arrays to save memery space c++

mrby1235-May-10 11:07

mrby123

5-May-10 11:07

This set does not compile, too.

Declare:
void CC_procDlg::time(float**);

define:
void CC_procDlg::time(float (*delms)[6])
{ code }

Call:
time(delms)

Please correct

Re: how to delete arrays to save memery space c++

CPallini3-May-10 10:33

CPallini

3-May-10 10:33

In your original post, you allocated an array of 1000 pointers on the stack.

float * tim_var[1000];

then, for every pointer, you allocated a memory buffer (6 floats) on the heap.
for (i=0;i<1000;i++)
{
tim_var[i] = new float[6];
}

Heap-allocated memory must be explicitely released, hence

// clean-up
for (i=0;i<1000;i++)
{
  delete tim_var[i];
}

On the other hand, you must not release stack-allocated memory.
Smile | :)

Re: how to delete arrays to save memery space c++

mrby1234-May-10 8:43

mrby123

4-May-10 8:43

My intention is to release all memories. The following code was suggested by a guru. I tried however, seems a problem. I got error message when I run the program: (delete statements got problem).

"DAMAGE after normal block (#125) at 0x00E40610"

////////////////////////////////////////////////////////////////////////////
float **tim_va;

tim_va = new float*[1000];

for (int ix = 0; ix < 1000; ix++)
{
tim_va[ix] = new float[6];

for (int jy = 0; jy < 6; y++)
tim_va[ix][jy] = 0.0;
}

for (ix = 0; ix < 1000; ix++)
delete [] tim_va[ix];

delete [] tim_va;
//////////////////////////////////////////////////////////////////////////////

Re: how to delete arrays to save memery space c++

CPallini4-May-10 9:05

CPallini

4-May-10 9:05

The code you're reporting doesn't compile. However if you modify it in order to make the compiler happy, it will run fine. Smile | :)

Re: how to delete arrays to save memery space c++

mrby1234-May-10 9:16

mrby123

4-May-10 9:16

Thanks. Would you please modify the code to make it work ?

Thanks

Re: how to delete arrays to save memery space c++

CPallini4-May-10 9:40

CPallini

4-May-10 9:40

float **tim_va;

tim_va = new float*[1000];

for (int ix = 0; ix < 1000; ix++)
{
    tim_va[ix] = new float[6];

    for (int jy = 0; jy < 6; jy++)
        tim_va[ix][jy] = 0.0;
}

for (int ix = 0; ix < 1000; ix++)
    delete [] tim_va[ix];

delete [] tim_va;

Re: how to delete arrays to save memery space c++

mrby1234-May-10 9:50

mrby123

4-May-10 9:50

Hi

Thanks. The code you put are the same as I reported before. I can not see any difference.

Please check. I know you have a very clear concept according to you post before.

Re: how to delete arrays to save memery space c++

CPallini4-May-10 10:25

CPallini

4-May-10 10:25

mrby123 wrote:
The code you put are the same as I reported before. I can not see any difference.

If you cannot see the difference, please check better.
This thread cannot last forever, I suppose: Good luck.
Smile | :)

Re: how to delete arrays to save memery space c++

mrby1234-May-10 10:53

mrby123

4-May-10 10:53

The code I put in this forum has a typo. In fact, it was correct typed in my test program.
So your code is the same as the I reported. It not run, but compiled.

I do not think we are clear about this topic. I think if we are not clear, it needs to find out the truth.

Re: how to delete arrays to save memery space c++

mrby1234-May-10 10:33

mrby123

4-May-10 10:33

The code above compiled, but when run it, I got:
"Damage after normal block (#126) at 0X00406A0"

OpenMP dilemma

Chesnokov Yuriy3-May-10 5:17

Chesnokov Yuriy

3-May-10 5:17

I need to parallel for loop which processes some image data.
The problem is that there is one function call in that for loop which takes as the argument some object (class, struct) whose data is used for processing.
It leads to multiple threads access problems to a single object as they process its own part of the image.

Is there a solution to solve the problem or it needs to have as many copies of the object as the number of threads to avoid multiple access?

Чесноков

Re: OpenMP dilemma

C^hris L^osinger3-May-10 5:39

C^hris L^osinger

3-May-10 5:39

are the threads modifying this shared object ?

if so, you will at least need to synchronize access to the object - to make sure one thread isn't reading while another thread is writing. but it's impossible for us to say if threads will all need their own copy or not, without knowing what the threads are doing to the object.

if they are just reading from the object, they can probably all share one instance.

image processing toolkits | batch image processing

Re: For critical sections, #pragma omp single can be used as barriers.

Software_Developer3-May-10 6:09

Software_Developer

3-May-10 6:09

For critical sections, #pragma omp single can be used as barriers.
In a parallel region, there are often sections of code where limiting access to a single thread is desired,
such as when writing to a file in the middle of a parallel region.
In many of these cases it does not matter which thread executes this code,
as long as it is just one thread. OpenMP has #pragma omp single to do this.

#pragma omp parallel
{
    if(omp_get_thread_num() > 3) 
    {
        #pragma omp single    // May not be accessed by all threads
        x++;
    }
}

OpenMP features for multithreaded applications

http://msdn.microsoft.com/en-us/magazine/cc163717.aspx

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.