This has been resolved by always adding 1 millisecond to the time measured. The fix has been pushed to CVS and will appear in the next release (probably 1.5).

In some cases, for very short inputs, the --profile counts zero (0) milliseconds of execution time. This in turn will cause a divide by zero error when attempting to calculate the average parsing speed.

As reported by Lukas Zapletal:

Try to: gramm arithmetic.grammar --profile

Tokenizing a-test.data

Time elapsed:  0 millisec
Tokens found:  11
INTERNAL ERROR: ...
java.lang.ArithmeticException: / by zero
at net.percederberg.grammatica.Grammatica.profile(Grammatica.java:522)      
at net.percederberg.grammatica.Grammatica.main(Grammatica.java:175)

Bug is here:
System.out.println("  Time elapsed:  " + time + " millisec");
System.out.println("  Tokens found:  " + counter);
System.out.println("  Average speed: " + (counter / time) + "tokens/millisec"); * HERE - divide by zero *
System.out.println();