On 02/23/2014 09:29 PM, Dima Pasechnik wrote:
On 2014-02-23, Dima Pasechnik <[email protected]> wrote:
On 2014-02-23, Dima Pasechnik <[email protected]> wrote:
On 2014-02-21, Benoît Darties <[email protected]> wrote:
Here is the code I run
sage: p = MixedIntegerLinearProgram("Coin")
sage: x=p.new_variable(binary=True,dim=1)
sage: p.set_min(x[0], 0.0)
sage:
sage: result=p.get_values(x);
works for me in Sage 6.1.1 on OSX 10.6.8.
oops, in fact, this does crash in the latter case, too.
(I did get_values() instead of get_values(x)...)
As well as it does crash on Linux x86_64.
the remedy is very simple: Coin's getColSolution() returns NULL
in this case, and thus
return solution[variable]
in get_variable_value() produces this crash.
So one has to check for NULL and so something meaningful if it is
NULL, e.g.
if solution == NULL:
return []
else:
return solution[variable]
Not sure whether [] is the right value, perhaps 0 might be more
uniform accross different backends...
ideally, one should simply use "if solution" or "if not solution". In
this case, the following patch fixes the segv:
diff --git a/src/sage/numerical/backends/coin_backend.pyx
b/src/sage/numerical/backends/coin_backend.pyx
index 4083c79..96e47d3 100644
--- a/src/sage/numerical/backends/coin_backend.pyx
+++ b/src/sage/numerical/backends/coin_backend.pyx
@@ -826,7 +826,10 @@ cdef class CoinBackend(GenericBackend):
cdef double * solution
solution = <double*> self.model.solver().getColSolution()
- return solution[variable]
+ if solution:
+ return solution[variable]
+ else:
+ return []
cpdef int ncols(self):
r"""
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