Scene two act 1 - what is the purpose of Halment acting mad in front of Ophelia

My class and I just finished discussing this scene today as well. I like your questions, and there are probably many different answers, but this is what I think. At the end of Act 1, Hamlet declared that he would put an "antic disposition" on. So, he planned to act mad--perhaps so that he would be able to minimize his seeming threat to Claudius, to gather more information, to stall until he came up with a plan, to hide his true emotions, to provide a cover for his eventual act of revenge--insanity. He goes to Ophelia first perhaps to determine if she's with him or against him. He learns from his encounter with Ophelia, that she reports to her father who reports to Claudius. He can gather that she is not to be trusted. Yes, I think he loves her very much, but that this revenge thing has driven a wedge between them that cannot be dislodged. He cannot confide in Ophelia, so he must break off the relationship--something she's already done anyway. He upsets her but does not physically hurt her. He may be expressing his hurt that she has refused to see him (per her father's orders).