[SciPy-User] Wrapping a lapack function (attempt results seg fault)

josef.pktd@gmai... josef.pktd@gmai...
Sat Feb 6 17:07:57 CST 2010


On Sat, Feb 6, 2010 at 6:02 PM, Skipper Seabold <jsseabold@gmail.com> wrote:
> On Sat, Feb 6, 2010 at 5:45 PM,  <josef.pktd@gmail.com> wrote:
>> On Sat, Feb 6, 2010 at 3:10 PM, Skipper Seabold <jsseabold@gmail.com> wrote:
>>> All,
>>>
>>> I'm trying to wrap the lapack function dtgsen for the ordered generalized
>>> Schur decomposition given real valued arrays
>>> <http://linux.die.net/man/l/dtgsen>.  However, I'm getting a segmentation
>>> fault, and I have no idea why.  I was hoping someone might look at my work
>>> and see where I've gone wrong, as this is my first attempt at trying to do
>>> something like this.  One specific thing I wasn't sure about is when the
>>> lapack function calls for a LOGICAL type can this just be
>>>
>>> from ctypes import c_bool
>>> logical_true = c_bool(True)
>>>
>>> ?
>>>
>>> I've attached my functions and arrays that make a self-contained example.
>>>  Just put the two files in a directory and run.  When I do a gdb backtrace I
>>> receive the following output.
>>>
>>> (gdb) run ordqztest.py
>>>
>>> Starting program: /usr/bin/python ordqztest.py
>>>
>>> [Thread debugging using libthread_db enabled]
>>>
>>>
>>> Program received signal SIGSEGV, Segmentation fault.
>>> 0x00007ffff5015d7d in dtgsen_ () from /usr/lib/liblapack.so
>>> (gdb) backtrace
>>> #0  0x00007ffff5015d7d in dtgsen_ () from /usr/lib/liblapack.so
>>> #1  0x00007ffff6da8bec in ffi_call_unix64 ()
>>>    at
>>> /build/buildd/python2.6-2.6.4/Modules/_ctypes/libffi/src/x86/unix64.S:75
>>> #2  0x00007ffff6da82d3 in ffi_call (cif=0x7fffffffd810, fn=<value optimized
>>> out>,
>>>    rvalue=<value optimized out>, avalue=<value optimized out>)
>>>
>>>    at
>>> /build/buildd/python2.6-2.6.4/Modules/_ctypes/libffi/src/x86/ffi64.c:430
>>> #3  0x00007ffff6da2d64 in _call_function_pointer (pProc=<value optimized
>>> out>,
>>>    argtuple=<value optimized out>, flags=<value optimized out>,
>>> argtypes=<value optimized out>,
>>>    restype=<value optimized out>, checker=<value optimized out>)
>>>
>>>    at /build/buildd/python2.6-2.6.4/Modules/_ctypes/callproc.c:816
>>>
>>> #4  _CallProc (pProc=<value optimized out>, argtuple=<value optimized out>,
>>>
>>>    flags=<value optimized out>, argtypes=<value optimized out>,
>>> restype=<value optimized out>,
>>>    checker=<value optimized out>) at
>>> /build/buildd/python2.6-2.6.4/Modules/_ctypes/callproc.c:1163
>>> #5  0x00007ffff6d9abf7 in CFuncPtr_call (self=0xc2c2c0, inargs=0x18,
>>> kwds=<value optimized out>)
>>>    at /build/buildd/python2.6-2.6.4/Modules/_ctypes/_ctypes.c:3860
>>>
>>> #6  0x000000000041d6e7 in PyObject_Call (func=0xc2c2c0, arg=0xcb8360,
>>> kw=0xc63520)
>>>    at ../Objects/abstract.c:2492
>>>
>>> #7  0x00000000004a199c in do_call (f=0xcb98c0, throwflag=<value optimized
>>> out>)
>>>    at ../Python/ceval.c:3924
>>>
>>> #8  call_function (f=0xcb98c0, throwflag=<value optimized out>) at
>>> ../Python/ceval.c:3729
>>> #9  PyEval_EvalFrameEx (f=0xcb98c0, throwflag=<value optimized out>) at
>>> ../Python/ceval.c:2389
>>> #10 0x00000000004a40e0 in PyEval_EvalCodeEx (co=0x7ffff7f01f30,
>>> globals=<value optimized out>,
>>>    locals=<value optimized out>, args=0x9, argcount=<value optimized out>,
>>> kws=<value optimized out>,
>>>    kwcount=2, defs=0x7ffff7f0a7f8, defcount=4, closure=0x0) at
>>> ../Python/ceval.c:2968
>>> #11 0x00000000004a245f in fast_function (f=0xcb9660, throwflag=<value
>>> optimized out>)
>>>    at ../Python/ceval.c:3802
>>>
>>> #12 call_function (f=0xcb9660, throwflag=<value optimized out>) at
>>> ../Python/ceval.c:3727
>>> ---Type <return> to continue, or q <return> to quit---
>>>
>>> #13 PyEval_EvalFrameEx (f=0xcb9660, throwflag=<value optimized out>) at
>>> ../Python/ceval.c:2389
>>> #14 0x00000000004a40e0 in PyEval_EvalCodeEx (co=0x7ffff7f026c0,
>>> globals=<value optimized out>,
>>>    locals=<value optimized out>, args=0x8, argcount=<value optimized out>,
>>> kws=<value optimized out>,
>>>    kwcount=2, defs=0x7ffff3ea9e78, defcount=3, closure=0x0) at
>>> ../Python/ceval.c:2968
>>> #15 0x00000000004a245f in fast_function (f=0x928e00, throwflag=<value
>>> optimized out>)
>>>    at ../Python/ceval.c:3802
>>> #16 call_function (f=0x928e00, throwflag=<value optimized out>) at
>>> ../Python/ceval.c:3727
>>> #17 PyEval_EvalFrameEx (f=0x928e00, throwflag=<value optimized out>) at
>>> ../Python/ceval.c:2389
>>> #18 0x00000000004a40e0 in PyEval_EvalCodeEx (co=0x7ffff7f02378,
>>> globals=<value optimized out>,
>>>    locals=<value optimized out>, args=0x0, argcount=<value optimized out>,
>>> kws=<value optimized out>,
>>>    kwcount=0, defs=0x0, defcount=0, closure=0x0) at ../Python/ceval.c:2968
>>> #19 0x00000000004a41b2 in PyEval_EvalCode (co=0x0, globals=0xcb8360,
>>> locals=0xc63520)
>>>    at ../Python/ceval.c:522
>>> #20 0x00000000004c33a0 in run_mod (fp=0x919900, filename=<value optimized
>>> out>,
>>>    start=<value optimized out>, globals=<value optimized out>,
>>> locals=0x8b9270, closeit=1,
>>>    flags=0x7fffffffe100) at ../Python/pythonrun.c:1335
>>> #21 PyRun_FileExFlags (fp=0x919900, filename=<value optimized out>,
>>> start=<value optimized out>,
>>>    globals=<value optimized out>, locals=0x8b9270, closeit=1,
>>> flags=0x7fffffffe100)
>>>    at ../Python/pythonrun.c:1321
>>> #22 0x00000000004c3564 in PyRun_SimpleFileExFlags (fp=<value optimized out>,
>>>    filename=0x7fffffffe518 "ordqztest.py", closeit=1, flags=0x7fffffffe100)
>>>    at ../Python/pythonrun.c:931
>>> #23 0x0000000000418ab7 in Py_Main (argc=-135384960, argv=<value optimized
>>> out>) at ../Modules/main.c:599
>>> #24 0x00007ffff6fd0abd in __libc_start_main (main=<value optimized out>,
>>> argc=<value optimized out>,
>>>    ubp_av=<value optimized out>, init=<value optimized out>, fini=<value
>>> optimized out>,
>>>    rtld_fini=<value optimized out>, stack_end=0x7fffffffe218) at
>>> libc-start.c:220
>>> #25 0x0000000000417ca9 in _start () at ../sysdeps/x86_64/elf/start.S:113
>>>
>>> Any help or pointers would be appreciated, as I am a bit out of my depth.
>>>
>>> -Skipper
>>>
>>> _______________________________________________
>>> SciPy-User mailing list
>>> SciPy-User@scipy.org
>>> http://mail.scipy.org/mailman/listinfo/scipy-user
>>>
>>>
>>
>> according to http://www.netlib.org/lapack/double/dtgsen.f  you are
>> missing alphai  in the argument list.
>>
>
> Ah, that is true.  I wonder why it didn't complain about my arguments
> list.  I originally tried to do the complex version, but then realized
> I didn't need it as of yet.  Still seg faults though.
>
>> I don't have (or find) c_bool in python 2.5, so my tries are also unsuccessful.
>>
>
> This is where I think it might be tripping up, but I don't know if
> LOGICAL type can just be a c_int.

I tried this, but it wasn't successful, and I have no idea about these types

>
>> Maybe wrapping with f2py like the routines in scipy.linalg might be a
>> better choice than ctypes? However, I haven't seen a recipe how to do
>> it.
>>
>
> I guess I do have the fortran source file.  I will try this.  I think
> I should just have to add the f2py directives for the inputs/outputs
> and (fingers-crossed) it will work.

I didn't look carefully, but the netlib with dependencies has a lot of
files, so it might not be so easy to do it standalone.

Here is a open ticket that wraps a new function

http://projects.scipy.org/scipy/ticket/964

maybe good for inspiration

Josef

>
> Skipper
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