It didn't work for me. :(
sage: g=Graph([[0,1],[2,3]])
sage: g.lovasz_theta()
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-2-1d4d0397a94f> in <module>()
----> 1 g.lovasz_theta()
/home/shhu/Documents/SageMath/local/lib/python2.7/site-packages/sage/graphs/lovasz_theta.pyc
in lovasz_theta(graph)
78 tf.close()
79 lines = subprocess.check_output([os.path.join(SAGE_LOCAL,
'bin', 'theta'), tf_name])
---> 80 return float(lines.split()[-1])
ValueError: could not convert string to float: failed.
在 2016年5月10日星期二 UTC+3下午6:33:50，Dima Pasechnik写道：
>
> all this works for me just fine:
>
> sage: g=Graph([[0,1],[2,3]])
> sage: g.lovasz_theta()
> 2.0
> sage: G = graphs.CycleGraph(7)
> sage: V = Set(G.vertices())
> sage: L = []
> sage: for s in V.subsets():
> ....: L.append(G.subgraph(s))
> ....:
> sage: L[68].lovasz_theta()
> 2.0
>
> Can you try the following:
> sage: g=Graph([[0,1],[2,3]])
> sage: g.lovasz_theta()
>
>
>
> On Tuesday, May 10, 2016 at 2:32:04 PM UTC+1, Sihuang Hu wrote:
>>
>> The adjacency matrix of the graph is
>>
>> [0 1 0 0]
>> [1 0 0 0]
>> [0 0 0 1]
>> [0 0 1 0]
>>
>>
>> 在 2016年5月10日星期二 UTC+3下午4:30:06，Dima Pasechnik写道：
>>>
>>> What is your L[68] ?
>>> This is probably something like a graph without edges...
>>>
>>> On Tuesday, May 10, 2016 at 1:53:17 PM UTC+1, Sihuang Hu wrote:
>>>>
>>>> Thanks for the comments.
>>>> I have installed package 'csdp' before. I got this error after I
>>>> installed it.
>>>>
>>>> 在 2016年5月10日星期二 UTC+3下午3:32:59，vdelecroix写道：
>>>>>
>>>>> The error you get is quite strange. On my computer with sage-7.1 I got
>>>>>
>>>>> sage: graphs.CycleGraph(7).lovasz_theta()
>>>>> Traceback (most recent call last): ur ...
>>>>> PackageNotFoundError: the package 'csdp' was not found. You can
>>>>> install
>>>>> it by running 'sage -i csdp' in a shell
>>>>>
>>>>> Which is very explicit about what to do... could you install the csdp
>>>>> package and try again?
>>>>>
>>>>> On 10/05/16 06:58, Sihuang Hu wrote:
>>>>> > Hi guys,
>>>>> >
>>>>> > When I try to compute the lovasz theta number of some graph, it says
>>>>> that
>>>>> >
>>>>> > *ValueError: could not convert string to float: failed.:*G =
>>>>> > graphs.CycleGraph(7)
>>>>> > V = Set(G.vertices())
>>>>> > L = []
>>>>> > for s in V.subsets():
>>>>> > L.append(G.subgraph(s))
>>>>> >
>>>>> > L[68].lovasz_theta()
>>>>> >
>>>>> ---------------------------------------------------------------------------
>>>>>
>>>>> > ValueError Traceback (most recent
>>>>> call last)
>>>>> > <ipython-input-53-0ad2fb49c2b1> in <module>()
>>>>> > ----> 1 L[Integer(68)].lovasz_theta()
>>>>> >
>>>>> >
>>>>> /home/shhu/Documents/SageMath/local/lib/python2.7/site-packages/sage/graphs/lovasz_theta.pyc
>>>>>
>>>>>
>>>>> > in lovasz_theta(graph)
>>>>> > 78 tf.close()
>>>>> > 79 lines =
>>>>> subprocess.check_output([os.path.join(SAGE_LOCAL,
>>>>> > 'bin', 'theta'), tf_name])
>>>>> > ---> 80 return float(lines.split()[-1])
>>>>> >
>>>>> > ValueError: could not convert string to float: failed.
>>>>> >
>>>>> > Thanks in advance!
>>>>> >
>>>>>
>>>>
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