memory allocation and new

[Wing]

Hi,

I use the following code to allocate 2D array:

**************
int n=10000;
double **array;

array=new double*[n];
assert(array);

for( int i = 0 ; i < n ; i++ )
{
array[i] = new double[n];
assert(array[i]);
}

****************

I would like to initialize each element in the 2D array to be a
constant number, say c. Although I can use double for-loops to do that,
it seems very time consuming.

Can I use other methods to initialize the 2D array? How about memset()?

Thank you.

[CppFans]

use the stl:
vector<vector<double> > array;

or:
const int N = 10000;
double array[N][N];

[CppFans]

use the stl:
vector<vector<double> > array;

or:
const int N = 10000;
double array[N][N];

[Jacek Dziedzic]

Wing wrote:

Hi,

I use the following code to allocate 2D array:

**************
int n=10000;
double **array;

array=new double*[n];
assert(array);

for( int i = 0 ; i < n ; i++ )
{
array[i] = new double[n];
assert(array[i]);
}

****************

I would like to initialize each element in the 2D array to be a
constant number, say c. Although I can use double for-loops to do that,
it seems very time consuming.
Get rid of the asserts. If new fails it throws std::bad_alloc,
and does not return NULL.
Can I use other methods to initialize the 2D array? How about memset()?

You could initialize one row/column using a for loop
and then memcpy() it to other rows/columns.

HTH,
- J.