Re: [Gsl-shell-info] Is there a function to compute matrix powers or the matrix exponential?

[Martin Felis]

Hi Francesco,

thanks for your checks and reply.

I found the problem on my side: I had LUA_PATH using the command
'luarocks path'. If delete the environment variable LUA_PATH gsl-shell
works directly.

I tried to further investigate this, as it seemed odd to me that
gsl-shell has problems with the environment variable LUA_PATH. After
having a look at the code in luajit/src/lib_package.c:542 I figured,
that package.path is initialized using the environment variable of
LUA_PATH in which all occurences of ";;" are replaced with additional
default paths that are defined in luaconf.h in the #define LUA_PATH_DEFAULT.

After adding a double semicolon ";;" to LUA_PATH everything works.

Best regards,
Martin

P.S.: I also had a look at the standard Lua code at it has the same
behaviour. Am I lacking any common knowledge about package.path and
LUA_PATH here?


On 15.08.2013 21:47, Francesco Abbate wrote:
> 2013/8/14 Omar Antolín Camarena <address@hidden>:
>> Hi everyone,
>>
>> Does GSL Shell come with implementations of matrix powers (with
>> integral exponents) or the matrix exponential? I couldn't find any in
>> the documentation. (And I am not familiar with GSL, but a quick search
>> suggests that GSL doesn't have this either.)
> 
> Hi Omar,
> 
> unfortunately GSL Shell does not have the matrix exponential function
> neither it is provided by the GSL library.
> 
> I know that the matrix exponential function is very useful and it is
> already in the list of the functions that should be implemented but
> unfortunately I cannot guarantee any visibility for its
> implementation.
> 
> If anyone want to contribute an implementation that would be very
> welcome. After all GSL Shell is free software! :-)
> 
> In the mean time may be you can use the venerable technique of using
> the eigenvalues factorization of the matrix. When applicable this
> technique can be a good solution but this depend on you specific
> problem.
> 
> Best regards
> Francesco
> 


-- 
mail  : address@hidden
phone : +49 6221 544983
office: IWR | Speyerer Str 6 | Room 319 | 69115 Heidelberg | Germany