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Why the sequence isn't random?

akilguo (43)
Hi,
I have a function gen_graph() which calls the rand() function to generate number sequence and output the sequence into a file, and my main function has such a structure:
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int main()
{
  srand( time( 0 ) );
  for( size_t i = 0 ; i != 100 ; ++i )
  {
    ...
    gen_gdraph();
    ...
  }
}

after execution, i got 100 files, but all the files are exactly the same!!! Why?
How can i get 100 different files? Thanks.
closed account (z05DSL3A)
akilguo wrote:
I have a function gen_graph() which calls the rand() function to generate number sequence
It would help if you posted the code that is meant to generate the pseudo random numbers.
akilguo (43)
the code of gen_graph is as following:
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size_t gen_edge( size_t &row, size_t& column, size_t verNum, size_t *pt )
{	
	size_t v1, v2;
	v1 = rand() % verNum;
	v2 = rand() % verNum;

	return pt[ row * ( row - 1 ) / 2 + column ] ;
}


void gen_graph( size_t verNum, size_t egNum,ofstream & os )
{
	size_t row, column ;
        size_t *pmtrx = ...;
	...
	for( size_t i = 0 ; i != egNum ; ++i )
	{
		while( gen_edge( row, column, verNum,pmtrx ) );
		...
	}
	...
}

int main()
{
	srand( time( 0 ) );
	for( size_t i = 0 ; i != 100 ; ++i )
	{
		...
		gen_graph( 100,4000,outfile );
                ...
	}
	return 0 ;
}
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