[armedbear-devel] Pure threads and hashtables test

Mark Evenson evenson at panix.com
Sat Sep 28 09:19:22 UTC 2013

On Sep 27, 2013, at 9:28 PM, Mark Evenson <evenson at panix.com> wrote:

> On Sep 27, 2013, at 8:13 PM, "Alan Ruttenberg" <alanruttenberg at gmail.com> wrote:
>> Agreed. While the gethash and puthash should independently work, the combination of the two isn't thread safe. For example two processes could get the value in the ht before either has a chance to write back the increment. 
> A version that only adds to unique keys in the hash table, relying on the HASH-TABLE-COUNT value to indicate successful update.  The keys are the squares of the first eight primes, so the total threads spawned is eight.  the parameter to RUN now indicates how many squares of the given prime basis. But  still weirdness, in that the first thread which should increment the keys of the hashtable indexed by the powers of 2 doesn't seem to execute.  Something in my LOOP clause?
> <threaded-hash.lisp>

Indeed a faulty understanding of LOOP:

CL-USER> (loop :for n :in '(2 3 5 7 11 13 15 17) :doing (threads:make-thread (lambda () (format t "~A " n))))
3 5 7 11 13 15 17 
17 NIL

The value of "n" has already been incremented past the first member of the list when the closure is created with LAMBDA, so the thread with "2" never gets executed.

SLIME users: one needs to place the form (setf swank:*globally-redirect-io* t) in ~/.swank.lisp to get all the FORMAT output in the REPL buffer.  Otherwise look in the corresponding *inferior-lisp* buffer.

So, I guess one should loop over closures that have been correctly initialized with the right values in some other manner.  I'd go for using DO over LOOP for unless someone can correct my understanding.  Either that, or I need to follow macro expansions.

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