bug#26616: guile-2.2 par-for-each hangs for large lists

bug#26616: guile-2.2 par-for-each hangs for large lists

[Linas Vepstas]

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The following spins, burning about 250% cpu time, for large lists; it works
fine for smaller lists.   This is for a recent version of guile from git:

guile -v
guile (GNU Guile) 2.1.5.19-7e9395

will retry with newer guile shortly.

On fresh guile:

(use-modules (srfi srfi-1))
(define al (list-tabulate 100000 values))
(define foo 0)
(par-for-each (lambda (x) (set! foo (+ x foo))) al)

^CERROR: In procedure scm-error:
ERROR: User interrupt

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
scheme@(guile-user) [1]> ,bt
In ice-9/threads.scm:
   289:22  5 (loop _)
In ice-9/futures.scm:
   265:11  4 (touch #<future 55e1984d3400 started #<procedure 55e198659f60
a…>)
   243:14  3 (work)
In unknown file:
           2 (wait-condition-variable #t)
While executing meta-command:
ERROR: In procedure cdr: Wrong type argument in position 1 (expecting
pair): ()
scheme@(guile-user) [1]>

The above is after interrupting after an hour or so of accumulated CPU
time.

Again, shorter lists (e.g. 10K long) work fine. My production lists are
about 400K to 2M in size.

--linas

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bug#26616: close

[Linas Vepstas]

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I just retested with a pull from today's git and the problem does NOT
reproduce.

Attempting to close this bug.

tested with

$ guile --version
guile (GNU Guile) 2.2.2.1-886ac

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bug#26616: close

[Linas Vepstas]

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Per last message, close.

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bug#26616: also a bug in guile-2.0.11

[Linas Vepstas]

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I just noticed that this bug DOES reproduce in guile 2.0.11 which is the
version that ships with Ubuntu Xenial (Ubuntu 16.04) ....

The above loop took 37 cpu-minutes to execute. The non-parallel version
executes instantly (fractions of a cpu-second).

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