The comparison between multimap objects is based on a pairwise comparison of their elements. The less than or equal to relationship between two objects is based on a comparison of the first pair of unequal elements.

// multimap_op_le.cpp
// compile with: /EHsc
#include <map>
#include <iostream>
int main( )
{
using namespace std;
multimap <int, int> m1, m2, m3, m4;
int i;
typedef pair <int, int> Int_Pair;
for ( i = 1 ; i < 3 ; i++ )
{
m1.insert ( Int_Pair ( i, i ) );
m2.insert ( Int_Pair ( i, i * i ) );
m3.insert ( Int_Pair ( i, i - 1 ) );
m4.insert ( Int_Pair ( i, i ) );
}
if ( m1 <= m2 )
cout << "m1 is less than or equal to m2" << endl;
else
cout << "m1 is greater than m2" << endl;
if ( m1 <= m3 )
cout << "m1 is less than or equal to m3" << endl;
else
cout << "m1 is greater than m3" << endl;
if ( m1 <= m4 )
cout << "m1 is less than or equal to m4" << endl;
else
cout << "m1 is greater than m4" << endl;
}

m1 is less than or equal to m2
m1 is greater than m3
m1 is less than or equal to m4