I will explain how to make sage have a segmentation fault with the following alarming message:
------------------------------------------------------------ Unhandled SIGSEGV: A segmentation fault occured in SAGE. This probably occured because a *compiled* component of SAGE has a bug in it (typically accessing invalid memory) or is not properly wrapped with _sig_on, _sig_off. You might want to run SAGE under gdb with 'sage -gdb' to debug this. SAGE will now terminate (sorry). ------------------------------------------------------------ Apply the following patch to sage-4.3.rc0: http://sporadic.stanford.edu/bump/patches/coerce_actions_segfault.patch This creates a file called sage/algebras/iwahori.py. Eventually it will make the Iwahori Hecke algebra of a Weyl group but at the moment it just makes the group algebra. You can do stuff like this: sage: H = WeylGroupAlgebra("B3") sage: [T1,T2,T3]=H.simple_reflections() sage: (T2*T3)^4 1 sage: (T1*T2)^3 1 Unfortunately you can get a crash by evaluating 2*T1. A backtrace with gdb shows frames in coerce_actions.c, coerce.c, parent.c, parent_old.c and element.c, all in sage/structure/ with corresponding cython files *.pyx. To get the backtrace, run sage -gdb, make it crash, then type bt at the gdb prompt. Examination of the backtrace led to the following more direct way of causing the crash: sage: WeylGroupAlgebra("A2").get_action(ZZ) I can probably work around this by writing a new _get_action_ method, so maybe this is not such a severe bug. But I am reporting it here. If it is deemed severe I will make a trac ticket. Daniel Bump -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
