I'm using SBCL 1.0.25 on AMD64 and SBCL 1.0.17 on a 32-bit box. By nonsense results I mean wrong results: the second return value contains only zeros. When SBCL crashes I either get a SB-SYS:MEMORY-FAULT-ERROR or "fatal error encountered in SBCL pid 31660(tid 140110828128592): no scavenge function for object 0x79109fe4 (widetag 0xe4)". This definitely looks like an SBCL bug.

Viktor

On Mon, Mar 9, 2009 at 12:27 AM, Liam Healy lhealy@common-lisp.net wrote:

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@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