float min_progress = FLT_MAX;
for (map<boost::thread::id, float>::const_iterator i = _digest_progresses.begin(); i != _digest_progresses.end(); ++i) {
min_progress = min (min_progress, i->second);
float min_progress = FLT_MAX;
for (map<boost::thread::id, float>::const_iterator i = _digest_progresses.begin(); i != _digest_progresses.end(); ++i) {
min_progress = min (min_progress, i->second);