How to clear cache memory on linux machine for a user

Question

I am running a c++ tool on Linux machine. The tool crashes because of memory issues. I have checked the RAM details of my machine.

             total       used       free     shared    buffers     cached
Mem:         15798      15747         50          0         15      12758
-/+ buffers/cache:       2972      12825
Swap:         8001        345       7655

There is hardly no space to run my application. How can I safely clear the selected cache memory so that the tool executes.(To do that how can I list the cache memory details) I need at least 3GB of memory to run my application.

I did not try to erase cache as it may kill the current application.

Note: The tool takes at least 40 hours to reach memory threshold limit. RedHat Linux

Please help.