why apache server cause the computer usage run until 100%?

[CstAn]

the system that i code was timetable scheduling system. in the created timetable i had use the random number for the teaching time for particular subject.
so, i had code for the random function for the random time function. i had try the function, it sometime able to produce the result but some time it not able to produce the result and cause the computer usage run until 100%. (after i restart the apache server then the computer usage as normal).

the random time is more than 50 time. and this also mean that i had make query to the database as more that 50 time.

what are the problem for me? until now i still cant get it.
hope anyone can help me. thanks.