Multy-thread md5/sha1 bruteforce?

[evilgravedigger]

Hi there.
I'm coding md5/sha1 CPU bruteforce tool (I know that GPU bruters are million times faster etc, I only code it for learning). My question is mostly about algorithm.
For example, I use 1 thread for bruteforcing passwords from AAAAA to ZZZZZ.
How to use second thread? My idea was - bruteforce "from the end", from ZZZZZ to AAAAA. Okay, works fine, works faster. But with my core i3 I still have 2 threads avalible (4 virtual cores, CPU usage with 2 threads is 50%).
How can I use 50% of free CPU (2 threads) to increase bruteforce speed?

[c4s]

The obvious way would be to do the following:
1. Thread starts from 0%
2. Thread starts from 25%
3. Thread starts from 50%
4. Thread starts from 75%

[evilgravedigger]

The obvious way would be to do the following:
1. Thread starts from 0%
2. Thread starts from 25%
3. Thread starts from 50%
4. Thread starts from 75%

Of course I understand, understand, but how to implement the idea?
1 thread - from AAAA to BBBB
2 thread - from CCCC to DDDD
etc

So if password is AADD no thread would find it. Because the first one does not work with D and second one does not know about A. That's the problem.

[c4s]

Well, how about incrementing differently?
1. Thread: AAA, AAB, AAC ...
2. Thread: BAA, BAB, BAC ...