Custom Query (1030 matches)

A colleague noticed that the following function can run more slowly with a suitable type declaration. I've reproduced his results on Linux:

Welcome to Clozure Common Lisp Version 1.12-dev-r16729M-trunk (LinuxX8664)!

Here are the commands:

(declaim (OPTIMIZE (COMPILATION-SPEED 0) (DEBUG 0) (SPEED 3) (SPACE 0) (SAFETY 0)))
(defun fibonacci (n)
  (declare (type (integer 0 *) n))
  (if (= n 0)
      0
    (if (= n 1)
        1
      (+ (fibonacci (- n 1)) (fibonacci (- n 2))))))

Then:

? (time (fibonacci 38))
(FIBONACCI 38)
took 912,371 microseconds (0.912371 seconds) to run.
During that period, and with 8 available CPU cores,
     912,812 microseconds (0.912812 seconds) were spent in user mode
         804 microseconds (0.000804 seconds) were spent in system mode
 1 minor page faults, 0 major page faults, 0 swaps.
39088169
? 

But here we see the time cut in more than half when we remove the type declaration:

? (time (fibonacci 38))
(FIBONACCI 38)
took 383,980 microseconds (0.383980 seconds) to run.
During that period, and with 8 available CPU cores,
     382,068 microseconds (0.382068 seconds) were spent in user mode
       2,433 microseconds (0.002433 seconds) were spent in system mode
 1 minor page faults, 0 major page faults, 0 swaps.
39088169
? 

It seems very surprising to get a segmentation fault with safety 3. Below are instructions from the README file of the attached gzipped tarfile, which show how to re-create that behavior. This example is a lightly modified version of a real problem we are having, where we cannot debug the problem because of the segmentation fault. Note: We did this on linux:

dunnottar:~% uname -a Linux dunnottar 3.13.0-110-generic #157-Ubuntu SMP Mon Feb 20 11:54:05 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux dunnottar:~%

But we have seen this problem on Mac as well.

Note: We have reproduced this bug using this CCL

Welcome to Clozure Common Lisp Version 1.12-dev-r16783M-trunk (LinuxX8664)!

but also ones as recent as last weekend.

.....

wget https://github.com/acl2-devel/acl2-devel/releases/download/7.3/acl2-7.3.tar.gz
tar xfz acl2-7.3.tar.gz
# Save disk space
rm -rf acl2-7.3/books
rm acl2-7.3.tar.gz
cd acl2-7.3
(time nice make LISP=ccl ACL2_SAFETY=3) >& make-safety-3.log
cd ..
./acl2-7.3/saved_acl2
(value :q)
(load "clrat-parser.lisp")
(clrat-read-file "R_4_4_18.clrat" state)

The ccl-documentation.html does not mention *command-line-argument-list*. I believe it should. :)

If you supply me with a specification of CCL command line argument handling, I offer writing the missing documentation myself.

Cheers, max

PS: Thanks for the great work on ccl!