Hey @Hemendra_Pal,
Welcome to the community. You are not supposed to post your queries in any existing post randomly. This might lead to your query being neglected. If you can’t find an existing query related to yours, then we would urge you to make a new post specific to your query in the appropriate forum. For more information regarding this, refer to 01 of this thread.
Now coming to your query, this anomaly clearly indicates that your implementation of cofi_cost_func is wrong. Please DM your code for the same to me. For learning how to DM, please check out 15 of the above-mentioned thread.
Cheers,
Elemento