I used the app to search for names in a directory with 20 text files (from 247KB up to 3927KB). The search uses regular expressions and ignores case. This app can really search for what I need to look for in the document. On my mobile phone (2 Cores 1.2GHz)  the search process takes about 30 seconds  maybe up to 40 seconds to check the result for all the files. The same search process takes about 15 to 20 seconds On a tablet pc (4 Cores 1.3GHz). My default document viewer is having trouble opening these moderately big sized txt files but with aGrep  opening and viewing the text within the search results is amazingly fast. It is also easy to cancel the searching so you can quickly change the search parameters if you made a mistake on your input. (Doing all this search process on a mainstream desktop PC will display the results instantaneously) I don't know if it is about my Phone's processing power that the search result takes some time. From the apps that I have tried out so far  this is the only one that can do the task. Now  I'm just checking if there are other apps that can do it faster.
April 13 2016