A computer-implemented method for determining specifications of the input of a manufacturing operation that outputs a part having cut-outs, the manufacturing operation consisting in forming the cut-outs via stamping, machining, milling and/or laser cutting, the method comprising: - providing specifications (FIG. 4) of the output part, including a user-designed B-Rep having cycles (a-m) of edges and modeling the part, the cut-outs being represented by the user with tunnels in the B-Rep; - determining, from equivalence classes of non-boundary cycles of edges of the B-Rep with respect to the cycle-homology relationship, the set that consists of all cycles being the one having the smallest length in a respective equivalence class; - performing a process on the set that includes iterating: • replacing a cycle of the set by its sum with an adjacent boundary cycle when this reduces the length; • for a cycle of the set and its sum with a shorter cycle of the set, deleting the cycle when the sum results in a boundary cycle, otherwise replacing the cycle by the sum when this reduces the length; - then, identifying among the cycles of the set a number n of cycles (a-b) as location of tunnels, wherein n is the genus of the B-Rep; and then - editing the B-Rep by removing identified tunnels and filling the empty space; - outputting the specifications (FIG. 5) of the output part with the edited B-Rep; wherein the identifying of location of tunnels includes, for each cycle of the set, calculating a value representative of the consistence, along the cycle, between the direction of the curvature of the cycle and the outside normal of the B-Rep, the n cycles having the highest value being then identified as location of tunnels, wherein the equivalence classes are identified within a basis of elementary cycles, each cycle of the B-Rep being obtainable by a sum of elementary cycles, and wherein the basis of elementary cycles is determined by computing a covering tree of the B-Rep, each elementary cycle corresponding to a respective edge outside the covering tree and being defined by adding the respective edge to the covering tree. - providing specifications (FIG. 4) of the output part, including a user-designed B-Rep having cycles (a-m) of edges and modeling the part, the cut-outs being represented by the user with tunnels in the B-Rep; - determining, from equivalence classes of non-boundary cycles of edges of the B-Rep with respect to the cycle-homology relationship, the set that consists of all cycles being the one having the smallest length in a respective equivalence class; - performing a process on the set that includes iterating: • replacing a cycle of the set by its sum with an adjacent boundary cycle when this reduces the length; • for a cycle of the set and its sum with a shorter cycle of the set, deleting the cycle when the sum results in a boundary cycle, otherwise replacing the cycle by the sum when this reduces the length; • replacing a cycle of the set by its sum with an adjacent boundary cycle when this reduces the length; • for a cycle of the set and its sum with a shorter cycle of the set, deleting the cycle when the sum results in a boundary cycle, otherwise replacing the cycle by the sum when this reduces the length; - then, identifying among the cycles of the set a number n of cycles (a-b) as location of tunnels, wherein n is the genus of the B-Rep; and then - editing the B-Rep by removing identified tunnels and filling the empty space; - outputting the specifications (FIG. 5) of the output part with the edited B-Rep;