GMRES iteration number
Hi, Is there any way to access the number of iterations it takes to complete a GMRES computation? I've checked the documentation at http://docs.scipy.org/doc/scipy-0.13.0/reference/generated/scipy.sparse.lina... and it doesn't appear so. I am doing some testing with passing in initial guesses x0, and I am interested to know whether or not this significantly reduces the required number of iterations. Thanks, Jonathan Tu
AFAICT no. On Thu, May 29, 2014 at 1:20 PM, Jonathan Tu <jonathantu@gmail.com> wrote:
Hi,
Is there any way to access the number of iterations it takes to complete a GMRES computation? I've checked the documentation at http://docs.scipy.org/doc/scipy-0.13.0/reference/generated/scipy.sparse.lina... and it doesn't appear so. I am doing some testing with passing in initial guesses x0, and I am interested to know whether or not this significantly reduces the required number of iterations.
Thanks, Jonathan Tu
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On Fri, May 30, 2014 at 10:37 AM, Arun Gokule <arun.gokule@gmail.com> wrote:
AFAICT no.
On Thu, May 29, 2014 at 1:20 PM, Jonathan Tu <jonathantu@gmail.com> wrote:
Hi,
Is there any way to access the number of iterations it takes to complete a GMRES computation? I've checked the documentation at http://docs.scipy.org/doc/scipy-0.13.0/reference/generated/scipy.sparse.lina... and it doesn't appear so. I am doing some testing with passing in initial guesses x0, and I am interested to know whether or not this significantly reduces the required number of iterations.
There's no return value that tells you tells (and we can't add one in nice a backwards-compatible way), but you can use a callback function to do this. Just provide a callback that increments some counter each time it is called. Ralf
Thanks, Jonathan Tu
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Hi, Using a callback makes sense to me conceptually, but I have never implemented something like this. Is there a standard way to do such a thing? I would like something lightweight, obviously. I can imagine defining a small class containing a counter attribute and a parens function that updates this value. This seems better than doing something like defining a global variable that callback() can modify. Since the callback function will be called as callback(rk), where rk is the residual, I don't know how else to have it update a value whose scope needs to lie outside the callback function itself. Jonathan Tu On May 30, 2014, at 1:47 AM, Ralf Gommers <ralf.gommers@gmail.com> wrote:
On Fri, May 30, 2014 at 10:37 AM, Arun Gokule <arun.gokule@gmail.com> wrote: AFAICT no.
On Thu, May 29, 2014 at 1:20 PM, Jonathan Tu <jonathantu@gmail.com> wrote: Hi,
Is there any way to access the number of iterations it takes to complete a GMRES computation? I've checked the documentation at http://docs.scipy.org/doc/scipy-0.13.0/reference/generated/scipy.sparse.lina... and it doesn't appear so. I am doing some testing with passing in initial guesses x0, and I am interested to know whether or not this significantly reduces the required number of iterations.
There's no return value that tells you tells (and we can't add one in nice a backwards-compatible way), but you can use a callback function to do this. Just provide a callback that increments some counter each time it is called.
Ralf
Thanks, Jonathan Tu
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Would it be possible to make the callback function an append operation on a list? e.g. create some list "residuals = []" and do "callback=residuals.append". Then the length of the list would tell you how many calls were made, and you would know what the residuals were along the way. Alternatively, I imagine you could do something like this: class Counter(object): def __init__(self): self.i = 0 def __str__(self): return str(self.i) def addone(self, OPTIONAL_IGNORED_INPUT=None): self.i += 1 blah = Counter() gmres(..., callback=blah.addone) print blah Eric On 6/9/2014 3:18 PM, Jonathan Tu wrote:
Hi,
Using a callback makes sense to me conceptually, but I have never implemented something like this. Is there a standard way to do such a thing? I would like something lightweight, obviously. I can imagine defining a small class containing a counter attribute and a parens function that updates this value. This seems better than doing something like defining a global variable that callback() can modify. Since the callback function will be called as callback(rk), where rk is the residual, I don't know how else to have it update a value whose scope needs to lie outside the callback function itself.
Jonathan Tu
On May 30, 2014, at 1:47 AM, Ralf Gommers <ralf.gommers@gmail.com <mailto:ralf.gommers@gmail.com>> wrote:
On Fri, May 30, 2014 at 10:37 AM, Arun Gokule <arun.gokule@gmail.com <mailto:arun.gokule@gmail.com>> wrote:
AFAICT no.
On Thu, May 29, 2014 at 1:20 PM, Jonathan Tu <jonathantu@gmail.com <mailto:jonathantu@gmail.com>> wrote:
Hi,
Is there any way to access the number of iterations it takes to complete a GMRES computation? I've checked the documentation at http://docs.scipy.org/doc/scipy-0.13.0/reference/generated/scipy.sparse.lina... and it doesn't appear so. I am doing some testing with passing in initial guesses x0, and I am interested to know whether or not this significantly reduces the required number of iterations.
There's no return value that tells you tells (and we can't add one in nice a backwards-compatible way), but you can use a callback function to do this. Just provide a callback that increments some counter each time it is called.
Ralf
Thanks, Jonathan Tu
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-- Eric Hermes J.R. Schmidt Group Chemistry Department University of Wisconsin - Madison
The lightest way to make a callback that keeps track of the number of times it is called is probably to use a closure: def make_callback(): closure_variables = dict(counter=0) # initialize variables in this # dict. The callback function # has access to this data. def callback(residuals): closure_variables["counter"] += 1 print closure_variables["counter"] return callback Then, generate the callback function using callback = make_callback() callback() # prints 1 callback() # prints 2 callback() # prints 3 To give a full example using "gmres": # ----------------------------------------------------------- import numpy as np from scipy.sparse.linalg import gmres # Generate random input data A = 5*np.eye(10) + np.random.random(size=(10,10)) b = np.random.random(size=(10,)) # Callback generator def make_callback(): closure_variables = dict(counter=0, residuals=[]) def callback(residuals): closure_variables["counter"] += 1 closure_variables["residuals"].append(residuals) print closure_variables["counter"], residuals return callback gmres(A,b,callback=make_callback()) # ----------------------------------------------------------- See also: "http://eev.ee/blog/2011/04/24/gotcha-python-scoping-closures/#the-other-prob..." for other ways to use closures to implement a counter. Pascal On Mon, 09 Jun 2014 15:34:57 -0500 Eric Hermes <ehermes@chem.wisc.edu> wrote:
Would it be possible to make the callback function an append operation on a list? e.g. create some list "residuals = []" and do "callback=residuals.append". Then the length of the list would tell you how many calls were made, and you would know what the residuals were along the way. Alternatively, I imagine you could do something like this:
class Counter(object): def __init__(self): self.i = 0 def __str__(self): return str(self.i) def addone(self, OPTIONAL_IGNORED_INPUT=None): self.i += 1
blah = Counter()
gmres(..., callback=blah.addone)
print blah
Eric
On 6/9/2014 3:18 PM, Jonathan Tu wrote:
Hi,
Using a callback makes sense to me conceptually, but I have never implemented something like this. Is there a standard way to do such a thing? I would like something lightweight, obviously. I can imagine defining a small class containing a counter attribute and a parens function that updates this value. This seems better than doing something like defining a global variable that callback() can modify. Since the callback function will be called as callback(rk), where rk is the residual, I don't know how else to have it update a value whose scope needs to lie outside the callback function itself.
Jonathan Tu
On May 30, 2014, at 1:47 AM, Ralf Gommers <ralf.gommers@gmail.com <mailto:ralf.gommers@gmail.com>> wrote:
On Fri, May 30, 2014 at 10:37 AM, Arun Gokule <arun.gokule@gmail.com <mailto:arun.gokule@gmail.com>> wrote:
AFAICT no.
On Thu, May 29, 2014 at 1:20 PM, Jonathan Tu <jonathantu@gmail.com <mailto:jonathantu@gmail.com>> wrote:
Hi,
Is there any way to access the number of iterations it takes to complete a GMRES computation? I've checked the documentation at http://docs.scipy.org/doc/scipy-0.13.0/reference/generated/scipy.sparse.lina... and it doesn't appear so. I am doing some testing with passing in initial guesses x0, and I am interested to know whether or not this significantly reduces the required number of iterations.
There's no return value that tells you tells (and we can't add one in nice a backwards-compatible way), but you can use a callback function to do this. Just provide a callback that increments some counter each time it is called.
Ralf
Thanks, Jonathan Tu
_______________________________________________ SciPy-User mailing list SciPy-User@scipy.org <mailto:SciPy-User@scipy.org> http://mail.scipy.org/mailman/listinfo/scipy-user
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On 10 June 2014 11:46, Pascal Bugnion <pascal@bugnion.org> wrote:
The lightest way to make a callback that keeps track of the number of times it is called is probably to use a closure:
I class can be simpler: class Callback(object): def __init__(self): self.counter = 0 def.__call__(self): self.counter += 1 callback = Callback() callback() callback() ...
participants (6)
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Arun Gokule -
Daπid -
Eric Hermes -
Jonathan Tu -
Pascal Bugnion -
Ralf Gommers