The search ranges for these two parameters were:  : 0.1, 0.2, …, 0.9 k : 5, 10, 15, …, 45 As it turned out, for many instances, the optimal value of with respect to MAP was either 0.1 or 0.2, suggesting the initial retrieval scores have valuable information inside them.
the optimal value of was between 20 and 40.