[sage-support] Sage Crash Report
Thanks
Jacques
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***
IPython post-mortem report
{'commit_hash': u'b467d487e',
'commit_source': 'installation',
'default_encoding': 'UTF-8',
'ipython_path': '/usr/lib/python2.7/dist-packages/IPython',
'ipython_version': '5.5.0',
'os_name': 'posix',
'platform': 'Linux-4.18.0-16-generic-x86_64-with-Ubuntu-18.04-bionic',
'sys_executable': '/usr/bin/python',
'sys_platform': 'linux2',
'sys_version': '2.7.15rc1 (default, Nov 12 2018, 14:31:15) \n[GCC 7.3.0]'}
***
***
Crash traceback:
---
---
ImportError Python 2.7.15rc1: /usr/bin/python
Mon Mar 11 16:56:11 2019
A problem occurred executing Python code. Here is the sequence of function
calls leading up to the error, with the most recent (innermost) call last.
/usr/share/sagemath/bin/sage-ipython in ()
1 #!/usr/bin/env python
2 # -*- coding: utf-8 -*-
3 """
4 Sage IPython startup script.
5 """
6
7 from sage.repl.interpreter import SageTerminalApp
8
9 app = SageTerminalApp.instance()
---> 10 app.initialize()
global app.initialize = >
11 app.start()
in initialize(self=, argv=None)
/usr/lib/python2.7/dist-packages/traitlets/config/application.pyc in
catch_config_error(method=,
app=, *args=(None,), **kwargs={})
72 TRAITLETS_APPLICATION_RAISE_CONFIG_FILE_ERROR = False
73 else:
74 raise ValueError("Unsupported value for environment variable:
'TRAITLETS_APPLICATION_RAISE_CONFIG_FILE_ERROR' is set to '%s' which is none of
{'0', '1', 'false', 'true', ''}."% _envvar )
75
76
77 @decorator
78 def catch_config_error(method, app, *args, **kwargs):
79 """Method decorator for catching invalid config
(Trait/ArgumentErrors) during init.
80
81 On a TraitError (generally caused by bad config), this will print
the trait's
82 message, and exit the app.
83
84 For use on init methods, to prevent invoking excepthook on invalid
input.
85 """
86 try:
---> 87 return method(app, *args, **kwargs)
method =
app =
args = (None,)
kwargs = {}
88 except (TraitError, ArgumentError) as e:
89 app.print_help()
90 app.log.fatal("Bad config encountered during initialization:")
91 app.log.fatal(str(e))
92 app.log.debug("Config at the time: %s", app.config)
93 app.exit(1)
94
95
96 class ApplicationError(Exception):
97 pass
98
99
100 class LevelFormatter(logging.Formatter):
101 """Formatter with additional `highlevel` record
102
/usr/lib/python2.7/dist-packages/IPython/terminal/ipapp.pyc in
initialize(self=, argv=None)
301
302 return super(TerminalIPythonApp, self).parse_command_line(argv)
303
304 @catch_config_error
305 def initialize(self, argv=None):
306 """Do actions after construct, but before starting the app."""
307 super(TerminalIPythonApp, self).initialize(argv)
308 if self.subapp is not None:
309 # don't bother initializing further, starting subapp
310 return
311 # print self.extra_args
312 if self.extra_args and not self.something_to_run:
313 self.file_to_run = self.extra_args[0]
314 self.init_path()
315 # create the shell
--> 316 self.init_shell()
self.init_shell = >
317 # and draw the banner
318 self.init_banner()
319 # Now a variety of things that happen after the banner is
printed.
320 self.init_gui_pylab()
321 self.init_extensions()
322 self.init_code()
323
324 def init_shell(self):
325 """initialize the InteractiveShell instance"""
326 # Create an InteractiveShell instance.
327 # shell.display_banner should always be False for the terminal
328 # based app, because we call shell.show_banner() by hand below
329 # so the banner shows *before*
[sage-support] Re: simplification options
Hi Michael, On 2019-03-11, Michael Beeson wrote: > I tried various simplification functions.I suppose I could start over, > not using "symbolic expressions" but > declaring K to be a suitable field or ring, maybe a quadratic extension of > the field of rational functions in a. > That is probably the "right" way to do it. Probably! > But I wish there were a simpler way. Why do you think using a sub-optimal far too general tool (e.g., symbolic variables when in fact the problem is about polynomial) is "simpler"? Best regards, Simon -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
[sage-support] Re: simplification options
Le lundi 11 mars 2019 19:05:04 UTC+1, Michael Beeson a écrit :
>
> I appreciate Eric's post, and I do use subs sometimes, but it makes me
> nervous since
> it will happily substitute any old thing you tell it to, even an
> incorrect thing. So, if your idea
> is to check a computation, it is a dangerous thing.
>
In order to minimize the error risk in the substitution, note that you can
use the Python variable b defined as
b = sqrt(1-a^2)
in the argument of subs(), thereby avoiding any duplicate code. The whole
code becomes then
sage: var('p,q,r,a') # note: no b at this stage
(p, q, r, a)
sage: b = sqrt(1-a^2)
sage: eq = (p*a+r*b+q)^2
sage: eq = eq.expand(); eq
a^2*p^2 - a^2*r^2 + 2*sqrt(-a^2 + 1)*a*p*r + 2*a*p*q + 2*sqrt(-a^2 + 1)*q*r
+ q^2 + r^2
sage: eq.subs({b: SR.var('b')})
a^2*p^2 + 2*a*b*p*r - a^2*r^2 + 2*a*p*q + 2*b*q*r + q^2 + r^2
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[sage-support] Re: simplification options
On Monday, March 11, 2019 at 11:05:04 AM UTC-7, Michael Beeson wrote: > > I appreciate Eric's post, and I do use subs sometimes, but it makes me > nervous since > it will happily substitute any old thing you tell it to, even an > incorrect thing. So, if your idea > is to check a computation, it is a dangerous thing. True, if you put > only correct equations in, > you'll usually get correct ones out. > Checking a result is usually much easier: Take the original form of the equation, subtract the simplified form, and check that the difference is divisible by the relations you impose, such as b^2-(1-a^2). No special normal forms are required, just a divisibility test. This gets more complicated when there are more relations, because then you'll need an ideal membership test, but then you can just present that as "the computational tool" (plus, with a bit of luck you can extract the way in which the difference can be expressed in terms of the generating relations. The algorithm in principle encounters that information on the way) -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
[sage-support] Re: simplification options
I appreciate Eric's post, and I do use subs sometimes, but it makes me nervous since it will happily substitute any old thing you tell it to, even an incorrect thing. So, if your idea is to check a computation, it is a dangerous thing. True, if you put only correct equations in, you'll usually get correct ones out. -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
[sage-support] Re: simplification options
What about something like
sage: var('p,q,r,a')
(p, q, r, a)
sage: b = sqrt(1-a^2)
sage: eq = (p*a+r*b+q)^2
sage: eq = eq.expand(); eq
a^2*p^2 - a^2*r^2 + 2*sqrt(-a^2 + 1)*a*p*r + 2*a*p*q + 2*sqrt(-a^2 + 1)*q*r
+ q^2 + r^2
sage: b = var('b')
sage: eq.subs({sqrt(1-a^2): b})
a^2*p^2 + 2*a*b*p*r - a^2*r^2 + 2*a*p*q + 2*b*q*r + q^2 + r^2
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[sage-support] simplification options
In the following example I would like to make Sage realize that (p,q,r)
are constants and (a,b) are variables
so in the end everything should be expressed as a polynomial in a,b. In
particular b^2 should be rewritten as 1-a^2
(b and a are actually sin and cosine of something) but b should not be
rewritten as sqrt(1-a^2). And,
in the end the terms should be grouped so we see explicitly the
coefficients of a,b,1, and a^2. Of course this
example is simple enough to do by hand, but I want to know how to control
Sage enough to get this to happen in Sage.
I tried various simplification functions.I suppose I could start over,
not using "symbolic expressions" but
declaring K to be a suitable field or ring, maybe a quadratic extension of
the field of rational functions in a.
That is probably the "right" way to do it. But I wish there were a
simpler way. I'm writing a paper with
little snippets of Sage code with which the reader, who will be a
mathematician probably unfamiliar with SageMath,
can check the computations, or see how the computations can be checked.
So the code should be readable to such a person, ruling out the
introduction
of new fields.The code below is perfectly readable in that sense, but
it doesn't quite do the job.
def mar11b():
var('p,q,r,a,b')
b = sqrt(1-a^2)
lam = p*a + r*b + q
mu = r*a - p*b
lam = sqrt(N/2)
eq = lam^2 - (p*a+r*b+q)^2
eq = eq.expand()
print(eq)
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