Hi everyone,
With the latest patches for compiling using -std=c++0x and gcc 4.6, there are
sporadic failures for some Ruby regressions, e.g. last night:
*****
build/ALPHA_MOESI_hammer/tests/opt/quick/se/50.memtest/alpha/linux/memtest-ruby-MOESI_hammer
FAILED!
*****
build/ALPHA_MOESI_CMP_token/tests/opt/quick/se/60.rubytest/alpha/linux/rubytest-ruby-MOESI_CMP_token
FAILED!
*****
build/ALPHA_MOESI_CMP_token/tests/opt/quick/se/50.memtest/alpha/linux/memtest-ruby-MOESI_CMP_token
FAILED!
I suspect that this is due to the different implementation of the hash map
(used to be ext/hash_map, and is now unordered map) and the use of iterators to
traverse this map in parts of Ruby. For example, in StateMachine.py:
for (WaitingBufType::iterator buf_iter = m_waiting_buffers.begin();
buf_iter != m_waiting_buffers.end();
++buf_iter) {
for (MsgVecType::iterator vec_iter = buf_iter->second->begin();
vec_iter != buf_iter->second->end();
++vec_iter) {
if (*vec_iter != NULL) {
(*vec_iter)->reanalyzeAllMessages();
}
}
wokeUpMsgVecs.push_back(buf_iter->second);
}
I am not sure if this particular piece of code is the issue, but in general we
have to ensure that any iteration over a hashtable does not have _any ordering
dependency_ since nothing can be assumed about the order of the traversal. I
can try and look through some of the files, but would greatly appreciate if
someone more at home with Ruby could help and track down all the places where
iteration takes place and confirm that the behaviour is deterministic
independent of the order (or alternatively add an ordered container next to the
hash table for keeping an ordered list/vector etc).
Thanks,
Andreas
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