printf bug

I have the following kernel

kernel void generate_bi(global uint *sizes, global uint *bi)

{

    uint globalID0 = get_global_id(0);

    uint globalID1 = get_global_id(1);

    printf((__constant char*) "(%d, %d) Thread works\n", globalID0, globalID1);

}

I don't get all printf's on my screen. For example, when I launch 16x16 in a single workgroup, I get the following

(0, 0) Thread works

(1, 0) Thread works

(2, 0) Thread works

(3, 0) Thread works

(4, 0) Thread works

(5, 0) Thread works

(6, 0) Thread works

(7, 0) Thread works

(8, 0) Thread works

(9, 0) Thread works

(10, 0) Thread works

(11, 0) Thread works

(12, 0) Thread works

(13, 0) Thread works

(14, 0) Thread works

(15, 0) Thread works

(0, 1) Thread works

(1, 1) Thread works

(2, 1) Thread works

(3, 1) Thread works

(4, 1) Thread works

(5, 1) Thread works

(6, 1) Thread works

(7, 1) Thread works

(8, 1) Thread works

(9, 1) Thread works

(10, 1) Thread works

(11, 1) Thread works

(12, 1) Thread works

(13, 1) Thread works

(14, 1) Thread works

(15, 1) Thread works

(0, 2) Thread works

(1, 2) Thread works

(2, 2) Thread works

(3, 2) Thread works

(4, 2) Thread works

(5, 2) Thread works

(6, 2) Thread works

Any ideas?