Yes, sorry I jumped the gun. Thanks for clarifying.
But it still does not have anything to do with Optim :)
The problem is due to defining an inline function (line 43) that creates
closure over the "x_previous" variable. To test this, just comment that
line (and adjust the Optim.optimize call), the problem goes away.
A simpler version of the code that fails is as follows:
julia> function f()
for i=1:10
if i>2; println(z); end
z=2
g() = 2z
end
end
f (generic function with 1 method)
julia> f()
ERROR: z not defined
in f at none:3
A fix to get it to work is to declare the variable at the start of your
function. Similarly, adding a "local x_previous" at the top of your
function makes it work correctly. Remember, variables in Julia are lexical
in scope.
julia> function f()
local z
for i=1:10
if i>2; println(z); end
z=2
g()=2z
end
end
f (generic function with 1 method)
julia> f()
2
2
2
2
2
2
2
2
On Wednesday, 29 April 2015 02:23:28 UTC+1, Pooya wrote:
>
> If you comment out lines 42-49, you will see that it works fine!
>
> On Tuesday, April 28, 2015 at 9:20:49 PM UTC-4, Pooya wrote:
>>
>> Thanks, but I think "if iter > 2" (line 21) makes sure that x_previous
>> is defined in the previous iteration. Just to be clear, the condition to
>> check here was "g_norm > g_norm_old", but I changed it to get there as
>> early as the second iteration.
>>
>> On Tuesday, April 28, 2015 at 9:13:49 PM UTC-4, Avik Sengupta wrote:
>>>
>>> I'm seeing the error in line 22 of your gist where you are trying to
>>> print the current value of "x_previous". However, x_previous is first
>>> defined in line 38 of your gist, and so the error is correct and doesnt
>>> have anything to do with Optim, as far as I can see.
>>>
>>> On Wednesday, 29 April 2015 01:39:02 UTC+1, Pooya wrote:
>>>>
>>>> Hi all,
>>>>
>>>> I have a problem that has made me scratch my head for many hours now!
>>>> It might be something obvious that I am missing. I have a Newton-Raphson
>>>> code to solve a system of nonlinear equations. The error that I get here
>>>> does not have anything to do with the algorithm, but just to be clear, I
>>>> need to find the best possible solution if the equations are not solvable,
>>>> so I am trying to stop simulation when the direction found by
>>>> Newton-Raphson is not correct! In order to do that I put an if-loop in the
>>>> beginning of the main loop to take x from the previous iteration
>>>> (x_previous), but I get x_previous not defined! I am using the Optim
>>>> package to do a line search after the direction has been found by
>>>> Newton-Raphson. If Optim is not used, things work perfectly (I tried by
>>>> commenting out those lines of code). Otherwise I get the error I
>>>> mentioned.
>>>> My code is here: https://gist.github.com/prezaei85/372bde76012472865a94,
>>>> which solves a simple one-variable quadratic equation. Any thoughts are
>>>> very much appreciated.
>>>>
>>>> Thanks,
>>>> Pooya
>>>>
>>>
