[Retracted] Three-Dimensional Inversion of Borehole-Surface Resistivity Method Based on the Unstructured Finite Element

Algorithm 1

Limited Memory BFGS.

(1)	Set k = 1, choose initial model m0, integer m > 0 and initial matrix (the identity matrix);
(2)	Compute , where is selected to satisfy the Wolfe-Powell conditions;
(3)	If k> m then
	Discard the vector pair from the storage
	Compute and save ;
	end
(4)	Update using formula (7) for m times to obtain from formula (6);
(5)	Set k = k + 1, go to step 2.