rack one's brains without results
It's a waste of time. A waste of effort.
Idioms and allusions
[source] Volume 32 of Zhu Zi Yu Lei: "it's just a waste of effort to desecrate ghosts and gods without knowing the meaning of serving the people." In Wang Shouren's chuanxilu of the Ming Dynasty, "there is no need to waste any effort to fight for Zhu Lu."
Discrimination of words
Usage: used as an object or attributive
rack one's brains without results
suffer from both the outside and the inside - wài gǎn nèi shāng
like an egg knocking itself against a stone - yǐ luǎn tóu shí
throw away a brick in order to get a gem - pāo zhuān yǐn yù
The struggle between the two sides - wō jiǎo zhī zhēng