Re: [sage-support] segfault when plotting gamma function

Wed, 15 Apr 2015 11:30:18 -0700 

For the bug report:

sage: a = 319830986772877770815625*sqrt(pi)
sage: b = 1048576*gamma(41/2, 41/2*x)
sage: f = a - b
sage: plot(f, (R,0,1))  # works fine
sage: plot(f / sqrt(pi), (R,0,1))  # BOOM

Vincent

On 15/04/15 20:12, Viviane Pons wrote:

I'll do it, but I was hopping to get more context about it, also checking
if it wasn't known somewhere.

2015-04-15 14:09 GMT-04:00 Vincent Delecroix <[email protected]>:


Do you know how to open a ticket?


On 15/04/15 20:08, Viviane Pons wrote:


More context about this:

I'm here with Buck at PyCon and he said he actually had this line running
a
few years ago. I don't know anything about this stuff so it's difficult to
track what's wrong now.

But it's really bad, as you can see, it's not just a usual exception, it's
actually crashing Sage...

(also, this is on Sage 6.6 and I believe it was there before. Buck had the
error on the previous version and updated it to see if was fixed on 6.6)

Best

Viviane

2015-04-15 14:04 GMT-04:00 Vincent Delecroix <[email protected]>:

  Already the following fails


sage: integrated = -(gamma(1/2*k, 1/2*R*k) - gamma(1/2*k))/gamma(1/2*k)
sage: plot(integrated.subs(k=41), (R,0,6))
/home/vincent/bin/sage: line 134: 13683 Segmentation fault
"$SAGE_ROOT/src/bin/sage" "$@"



On 15/04/15 18:55, Buck Evan wrote:

  I'm trying to plot a function involving the gamma function. It's this

one:

-(gamma(1/2*k, 1/2*R*k) - gamma(1/2*k))/gamma(1/2*k)



If I try to plot the function with a k value any greater than 40, I get
a
segfault:


sum(
       plot(
           integrated(k=k),
           (x, 0, 2.5),
           ymax=1.6,
           color=color,
           legend_label='k=%i' % k,
           figsize=6,
           aspect_ratio=1.0,
       )
       for k, color in zip(
           [21, 22, 23, 26, 31, 41],
           ['blue', 'brown', 'red', 'green', 'black', 'yellow',
'orange'],
       )
)

/Users/buck/trees/mine/sage/sage: line 134: 12283 Segmentation fault:
11  "$SAGE_ROOT/src/bin/sage" "$@"
[I 12:15:10.735 NotebookApp] KernelRestarter: restarting kernel (1/5)


This is extremely similar to the behavior I was getting with the
pre-built
6.5 sage, so I think it's an old bug rather than a problem with my
build.
In 6.5 there was no output (I suspect the Segmentation Fault message was
gobbled somehow), so I never tried to enable / debug a core dump in 6.5.

Inspecting the 6.6 core dump, I see that it used 27528, mostly calling
back
and forth between two functions.
Smells like stack overflow to me.

(lldb) bt
                                                           [27503/47384]
* thread #1: tid = 0x0000, 0x0000000103588007
libpython2.7.dylib`vgetargskeywords + 23, stop reason = signal SIGSTOP
     * frame #0: 0x0000000103588007 libpython2.7.dylib`vgetargskeywords
+
23
       frame #1: 0x000000010358890e
libpython2.7.dylib`PyArg_ParseTupleAndKeywords + 174
       frame #2: 0x000000010356c40e libpython2.7.dylib`builtin___
import__
+ 94
       frame #3: 0x00000001034a377f
libpython2.7.dylib`PyObject_CallFunctionObjArgs + 367
       frame #4: 0x000000010774c1c4 coerce.so`__Pyx_Import(name=<
unavailable>,
from_list=0x0000000117da7560, level=<unavailable>) + 180 at coerce.c:
20339
       frame #5: 0x000000010774d08e
coerce.so`__pyx_f_4sage_9structure_6coerce_py_scalar_
parent(__pyx_v_py_type=<unavailable>,
__pyx_skip_dispatch=<
unavailable>) + 510 at coerce.c:2938
       frame #6: 0x0000000107760318
coerce.so`__pyx_f_4sage_9structure_6coerce_24CoercionModel_cache_maps_
canonical_coercion(__pyx_v_self=0x00000001
07648d50, __pyx_v_x=0x00007f8fbfc37238, __pyx_v_y=0x0000000118c5f390,
__pyx_skip_dispatch=<unavailable>) + 3128 at coerce.c:9585
       frame #7: 0x0000000107763cfe
coerce.so`__pyx_pw_4sage_9structure_6coerce_24CoercionModel_cache_maps_
25canonical_coercion
+ 13 at coerce.c:105
64
       frame #8: 0x0000000107763cf1
coerce.so`__pyx_pw_4sage_9structure_6coerce_24CoercionModel_cache_maps_
25canonical_coercion(__pyx_v_self=0x00000
00107648d50, __pyx_args=0x0000000117e5f248,
__pyx_kwds=0x0000000000000000)
+ 65
       frame #9: 0x0000000103574f10 libpython2.7.dylib`PyEval_EvalFrameEx
+
26208
       frame #10: 0x0000000103575fb0 libpython2.7.dylib`PyEval_EvalCodeEx
+
2144
       frame #11: 0x00000001034dae0c libpython2.7.dylib`function_call +
124
       frame #12: 0x000000010d680381
pynac.so`__Pyx_PyObject_Call(func=0x0000000108f0c410,
arg=<unavailable>,
kw=PyObject * at scalar) + 65 at pynac
.cpp:26785
       frame #13: 0x000000010d6a76e9
pynac.so`py_gcd(__pyx_v_n=0x00007f8fbfc37238,
__pyx_v_k=0x0000000118c5f390)
+ 521 at pynac.cpp:8416
       frame #14: 0x000000010d7d0f28
libpynac.1.dylib`GiNaC::gcd(GiNaC::numeric const&, GiNaC::numeric
const&) +
56
       frame #15: 0x000000010d7ad100
libpynac.1.dylib`GiNaC::add::integer_content() const + 496
       frame #16: 0x000000010d7acef0
libpynac.1.dylib`GiNaC::ex::integer_content() const + 16
       frame #17: 0x000000010d79fe01 libpynac.1.dylib`GiNaC::mul::
eval(int)
const + 1377
       frame #18: 0x000000010d71ba91
libpynac.1.dylib`GiNaC::ex::construct_from_basic(GiNaC::basic const&) +
113
       frame #19: 0x000000010d7a026b libpynac.1.dylib`GiNaC::mul::
eval(int)
const + 2507
       frame #20: 0x000000010d71ba91
libpynac.1.dylib`GiNaC::ex::construct_from_basic(GiNaC::basic const&) +
113
       frame #21: 0x000000010d7a026b libpynac.1.dylib`GiNaC::mul::
eval(int)
const + 2507
       frame #22: 0x000000010d71ba91
libpynac.1.dylib`GiNaC::ex::construct_from_basic(GiNaC::basic const&) +
113
       frame #23: 0x000000010d7a026b libpynac.1.dylib`GiNaC::mul::
eval(int)
const + 2507
       frame #24: 0x000000010d71ba91
libpynac.1.dylib`GiNaC::ex::construct_from_basic(GiNaC::basic const&) +
113
       frame #25: 0x000000010d7a026b libpynac.1.dylib`GiNaC::mul::
eval(int)
const + 2507
       frame #26: 0x000000010d71ba91
libpynac.1.dylib`GiNaC::ex::construct_from_basic(GiNaC::basic const&) +
113
       frame #27: 0x000000010d7a026b libpynac.1.dylib`GiNaC::mul::
eval(int)
const + 2507
       frame #28: 0x000000010d71ba91
libpynac.1.dylib`GiNaC::ex::construct_from_basic(GiNaC::basic const&) +
113
       frame #29: 0x000000010d7a026b libpynac.1.dylib`GiNaC::mul::
eval(int)
const + 2507
...
       frame #27502: 0x000000010d71ba91
libpynac.1.dylib`GiNaC::ex::construct_from_basic(GiNaC::basic const&) +
113
       frame #27503: 0x000000010d7a026b libpynac.1.dylib`GiNaC::mul::
eval(int)
const + 2507
       frame #27504: 0x000000010d71ba91
libpynac.1.dylib`GiNaC::ex::construct_from_basic(GiNaC::basic const&) +
113
       frame #27505: 0x000000010d7a026b libpynac.1.dylib`GiNaC::mul::
eval(int)
const + 2507
       frame #27506: 0x000000010d71ba91
libpynac.1.dylib`GiNaC::ex::construct_from_basic(GiNaC::basic const&) +
113
       frame #27507: 0x000000010d7a026b libpynac.1.dylib`GiNaC::mul::
eval(int)
const + 2507
       frame #27508: 0x000000010d71ba91
libpynac.1.dylib`GiNaC::ex::construct_from_basic(GiNaC::basic const&) +
113
       frame #27509: 0x000000010d7a026b libpynac.1.dylib`GiNaC::mul::
eval(int)
const + 2507
       frame #27510: 0x000000010d71ba91
libpynac.1.dylib`GiNaC::ex::construct_from_basic(GiNaC::basic const&) +
113
       frame #27511: 0x000000010d7a026b libpynac.1.dylib`GiNaC::mul::
eval(int)
const + 2507
       frame #27512: 0x000000010d71ba91
libpynac.1.dylib`GiNaC::ex::construct_from_basic(GiNaC::basic const&) +
113
       frame #27513: 0x000000010d7a026b libpynac.1.dylib`GiNaC::mul::
eval(int)
const + 2507
       frame #27514: 0x000000010d71ba91
libpynac.1.dylib`GiNaC::ex::construct_from_basic(GiNaC::basic const&) +
113
       frame #27515: 0x000000010d7a026b libpynac.1.dylib`GiNaC::mul::
eval(int)
const + 2507
       frame #27516: 0x000000010d71ba91
libpynac.1.dylib`GiNaC::ex::construct_from_basic(GiNaC::basic const&) +
113
       frame #27517: 0x000000010d7d1ccd
libpynac.1.dylib`GiNaC::operator*(GiNaC::ex const&, GiNaC::ex const&) +
77
       frame #27518: 0x000000010da76768
expression.so`__pyx_f_4sage_8symbolic_10expression_
10Expression__mul_(__pyx_v_left=0x0000000117db6cb0,
__pyx_v_right=0x0000000117db6ea8, __pyx_skip_dispatch=<unavailable>) +
2504
at expression.cpp:18109
       frame #27519: 0x00000001075bed30
element.so`__pyx_pw_4sage_9structure_7element_11RingElement_11__mul__ +
64
at element.c:17301
       frame #27520: 0x00000001075becf0
element.so`__pyx_pw_4sage_9structure_7element_
11RingElement_11__mul__(__pyx_v_left=0x0000000117db6cb0,
__pyx_v_right=0x0000000117db6ea8) + 14
       frame #27521: 0x000000010349ff8b libpython2.7.dylib`PyNumber_
Multiply
+
187
       frame #27522: 0x0000000117bceb47
wrapper_py.so`interp_py(args=0x0000000117dbeda8,
constants=0x00007f8fbd980f30, stack=<unavailable>,
code=0x00007f8fbd9a8eac)
+ 519 at interp_py.c:110
       frame #27523: 0x0000000117bc1cca
wrapper_py.so`__pyx_pw_4sage_3ext_12interpreters_10wrapper_
py_10Wrapper_py_5__call__(__pyx_v_self=0x00000001181db380,
__pyx_args=0x0000000117dbed90, __pyx_kwds=0x0000000000000000) + 138 at
wrapper_py.c:1478
       frame #27524: 0x00000001034a2bd3 libpython2.7.dylib`PyObject_Call
+
67
       frame #27525: 0x00000001035727bd libpython2.7.dylib`PyEval_
EvalFrameEx
+ 16141
       frame #27526: 0x0000000103575fb0 libpython2.7.dylib`PyEval_
EvalCodeEx
+
2144
       frame #27527: 0x000000010357513d libpython2.7.dylib`PyEval_
EvalFrameEx
+ 26765
       frame #27528: 0x000000010e399354


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