[Gsll-devel] SVD problem

[Liam Healy]

Viktor,

What version of SBCL are you running, and what do you mean by
"nonsense results"?
When I run sbcl 1.0.18.debian, I get an error from (test 1000) which
looks like it's in
the printing routine as it tries to return the answer matrix:
debugger invoked on a SB-SYS:MEMORY-FAULT-ERROR in thread #<THREAD
"initial thread" RUNNING {10039ADBF1}>:
  Unhandled memory fault at #x0.
Type HELP for debugger help, or (SB-EXT:QUIT) to exit from SBCL.
restarts (invokable by number or by possibly-abbreviated name):
  0: [ABORT] Exit debugger, returning to top level.
(SB-SYS:MEMORY-FAULT-ERROR)
0]
WARNING: Starting a select without a timeout while interrupts are disabled.
:ba
0: (SB-SYS:MEMORY-FAULT-ERROR)
1: (SB-SYS:MEMORY-FAULT-ERROR)[:EXTERNAL]
2: ("foreign function: #x41EAA2")
3: ("foreign function: #x41EB70")
4: ("foreign function: #x40D53D")
5: ("foreign function: #x41CA5C")
6: (SB-KERNEL::COLLECT-GARBAGE 0)
7: ((FLET SB-THREAD::WITH-MUTEX-THUNK))
8: ((FLET #:WITHOUT-INTERRUPTS-BODY-[CALL-WITH-MUTEX]477))
9: ((FLET #:WITHOUT-INTERRUPTS-BODY-[SUB-GC]60))
10: (SB-KERNEL:SUB-GC)[:EXTERNAL]
11: ("foreign function: #x41EAA2")
12: ("foreign function: #x40D435")
13: ("foreign function: #x4116C3")
14: (SB-BIGNUM:MULTIPLY-BIGNUM-AND-FIXNUM
     #<unavailable argument>
     #<unavailable argument>)
15: (SB-IMPL::FLONUM-TO-DIGITS
     0.006426902231453881d0
     #<unavailable argument>
     NIL)
16: (SB-IMPL::OUTPUT-FLOAT-AUX
     0.006426902231453881d0
     #<SB-PRETTY:PRETTY-STREAM {100631AE51}>
     -3
     8)
17: (SB-PRETTY:OUTPUT-PRETTY-OBJECT
     0.006426902231453881d0
     #<SB-PRETTY:PRETTY-STREAM {100631AE51}>)
18: ((FLET #:WITH-PRETTY-STREAM-2825) #<SB-PRETTY:PRETTY-STREAM {100631AE51}>)
19: ((LABELS SB-PRETTY::OUTPUT-GUTS)
     #<SB-PRETTY:PRETTY-STREAM {100631AE51}>
     0
     (1000))
20: ((FLET #:WITH-PRETTY-STREAM-2825) #<SB-PRETTY:PRETTY-STREAM {100631AE51}>)
21: ((LABELS SB-PRETTY::OUTPUT-GUTS)
     #<SB-PRETTY:PRETTY-STREAM {100631AE51}>
     0
     (1000 1000))
22: (SB-PRETTY:OUTPUT-PRETTY-OBJECT
     #2A((-0.03152179146033235d0 -0.0064356015982750805d0
          0.031318650821186636d0 0.021215786371980315d0 0.003314355400406193d0
          0.0033404976598180773d0 -0.024914202255263d0 0.022145320720119623d0
          -0.023703547290539858d0 0.010257175021330184d0
    ...
23: (PRINC
     #2A((-0.03152179146033235d0 -0.0064356015982750805d0
          0.031318650821186636d0 0.021215786371980315d0 0.003314355400406193d0
   ...

I didn't try (test 3000).
By the way, I tried Clozure  CL 1.2 on the same platform (Debian
amd64) with both
(test 1000) and (test 3000), and both run to completion and look
reasonable, so I
think at least what I'm seeing is a problem with SBCL.

Liam

On Sun, Mar 8, 2009 at 8:11 AM, Viktor Leis <viktor.leis at googlemail.com> wrote:
> Hi,
>
> I've got a problem with singular value decomposition: Big matrices
> (e.g. 3000x3000) crash SBCL. With a matrix of 1000x1000 it doesn't
> crash but instead I usually get nonsense results. With a small matrix
> (e.g. 500x500) it works perfectly fine. I get the same behavior on 32
> and 64 bit Linux.
>
> (defun test (n)
>  (let ((a (make-marray 'double-float :dimensions (list n n)))
>        (s (make-marray 'double-float :dimensions n))
>        (v (make-marray 'double-float :dimensions (list n n))))
>    (dotimes (i n)
>      (dotimes (j n)
>        (setf (maref a i j) (random 1.0d0))))
>    (multiple-value-list (sv-decomposition a s v))))
>
> Viktor Leis