On Thu, May 08, 2008 at 10:04:28AM -0600, Charles R Harris wrote:
What realistic probability is in the range exp(-1000) ?
I recently tried to do Fisher information estimation of a very noisy
experiment. For this I needed to calculate the norm of the derivation of
the probability over the
Hi,
For precision reasons, I almost always need to work with arrays whose
elements are log values. My thought was that it would be really neat
to have a 'logarray' class implemented in C or as a subclass of the
standard array class. Here is a sample of how I'd like to work with
these objects:
On Thu, May 8, 2008 at 12:26 AM, T J [EMAIL PROTECTED] wrote:
x = array([-2,-2,-3], base=2)
y = array([-1,-2,-inf], base=2)
z = x + y
z
array([-0.415037499279, -1.0, -3])
z = x * y
z
array([-3, -4, -inf])
z[:2].sum()
-2.41503749928
Whoops
s/array/logarray/
On Thu, May 8, 2008 at 1:26 AM, T J [EMAIL PROTECTED] wrote:
Hi,
For precision reasons, I almost always need to work with arrays whose
elements are log values. My thought was that it would be really neat
to have a 'logarray' class implemented in C or as a subclass of the
standard array
2008/5/8 David Cournapeau [EMAIL PROTECTED]:
On Thu, May 8, 2008 at 10:20 PM, Charles R Harris
[EMAIL PROTECTED] wrote:
Floating point numbers are essentially logs to base 2, i.e., integer
exponent and mantissa between 1 and 2. What does using the log buy you?
Precision, of
2008/5/8 Charles R Harris [EMAIL PROTECTED]:
What realistic probability is in the range exp(-1000) ?
Well, I ran into it while doing a maximum-likelihood fit - my early
guesses had exceedingly low probabilities, but I needed to know which
way the probabilities were increasing.
Anne
On Fri, May 9, 2008 at 1:04 AM, Charles R Harris
[EMAIL PROTECTED] wrote:
1e-308 ?
Yes, all the time. I mean, if it was not, why people would bother with
long double and co ? Why denormal would exist ? I don't consider the
comparison with the number of particules to be really relevant here.
On Fri, May 9, 2008 at 1:25 AM, Charles R Harris
[EMAIL PROTECTED] wrote:
But to expand on David's computation... If the numbers are stored without
using logs, i.e., as the exponentials, then the sum is of the form:
x_1*2**y_1 + ... + x_i*2**y_i
You missed the part on parametric models: in
On Thu, May 8, 2008 at 10:42 AM, David Cournapeau [EMAIL PROTECTED]
wrote:
On Fri, May 9, 2008 at 1:04 AM, Charles R Harris
[EMAIL PROTECTED] wrote:
1e-308 ?
Yes, all the time. I mean, if it was not, why people would bother with
long double and co ? Why denormal would exist ? I don't
On Thu, May 8, 2008 at 11:25 AM, Charles R Harris
[EMAIL PROTECTED] wrote:
On Thu, May 8, 2008 at 10:11 AM, Anne Archibald [EMAIL PROTECTED]
wrote:
2008/5/8 Charles R Harris [EMAIL PROTECTED]:
What realistic probability is in the range exp(-1000) ?
Well, I ran into it while doing a
On Thu, May 8, 2008 at 10:52 AM, David Cournapeau [EMAIL PROTECTED]
wrote:
On Fri, May 9, 2008 at 1:25 AM, Charles R Harris
[EMAIL PROTECTED] wrote:
But to expand on David's computation... If the numbers are stored without
using logs, i.e., as the exponentials, then the sum is of the
On Thu, May 8, 2008 at 10:56 AM, Robert Kern [EMAIL PROTECTED] wrote:
On Thu, May 8, 2008 at 11:25 AM, Charles R Harris
[EMAIL PROTECTED] wrote:
On Thu, May 8, 2008 at 10:11 AM, Anne Archibald
[EMAIL PROTECTED]
wrote:
2008/5/8 Charles R Harris [EMAIL PROTECTED]:
What realistic
On Thu, May 8, 2008 at 12:02 PM, Charles R Harris
[EMAIL PROTECTED] wrote:
On Thu, May 8, 2008 at 10:56 AM, Robert Kern [EMAIL PROTECTED] wrote:
On Thu, May 8, 2008 at 11:25 AM, Charles R Harris
[EMAIL PROTECTED] wrote:
On Thu, May 8, 2008 at 10:11 AM, Anne Archibald
[EMAIL PROTECTED]
: [Numpy-discussion] Log Arrays
On Thu, May 8, 2008 at 10:11 AM, Anne Archibald [EMAIL PROTECTED]
wrote:
2008/5/8 Charles R Harris [EMAIL PROTECTED]:
What realistic probability is in the range exp(-1000) ?
Well, I ran into it while doing a maximum-likelihood fit - my early
guesses had
On Fri, May 9, 2008 at 1:54 AM, Charles R Harris
[EMAIL PROTECTED] wrote:
Yes, and Gaussians are a delusion beyond a few sigma. One of my pet peeves.
If you have more than 8 standard deviations, then something is fundamentally
wrong in the concept and formulation.
If you have a mixture of
On Thu, 8 May 2008, Charles R Harris wrote:
On Thu, May 8, 2008 at 10:11 AM, Anne Archibald [EMAIL PROTECTED]
wrote:
2008/5/8 Charles R Harris [EMAIL PROTECTED]:
What realistic probability is in the range exp(-1000) ?
Well, I ran into it while doing a maximum-likelihood fit - my early
2008/5/8 Charles R Harris [EMAIL PROTECTED]:
On Thu, May 8, 2008 at 10:56 AM, Robert Kern [EMAIL PROTECTED] wrote:
When you're running an optimizer over a PDF, you will be stuck in the
region of exp(-1000) for a substantial amount of time before you get
to the peak. If you don't use the
On Thu, May 8, 2008 at 11:18 AM, David Cournapeau [EMAIL PROTECTED]
wrote:
On Fri, May 9, 2008 at 2:06 AM, Nadav Horesh [EMAIL PROTECTED]
wrote:
Is the 80 bits float (float96 on IA32, float128 on AMD64) isn't enough?
It has a 64 bits mantissa and can represent numbers up to nearly
On Thu, May 8, 2008 at 12:53 PM, Charles R Harris
[EMAIL PROTECTED] wrote:
On Thu, May 8, 2008 at 11:18 AM, David Cournapeau [EMAIL PROTECTED]
wrote:
On Fri, May 9, 2008 at 2:06 AM, Nadav Horesh [EMAIL PROTECTED]
wrote:
Is the 80 bits float (float96 on IA32, float128 on AMD64) isn't
On Thu, May 8, 2008 at 11:31 AM, Warren Focke [EMAIL PROTECTED]
wrote:
On Thu, 8 May 2008, Charles R Harris wrote:
On Thu, May 8, 2008 at 10:11 AM, Anne Archibald
[EMAIL PROTECTED]
wrote:
2008/5/8 Charles R Harris [EMAIL PROTECTED]:
What realistic probability is in the range
2008/5/8 Charles R Harris [EMAIL PROTECTED]:
David, what you are using is a log(log(x)) representation internally. IEEE
is *not* linear, it is logarithmic.
As Robert Kern says, yes, this is exactly what the OP and all the rest
of us want.
But it's a strange thing to say that IEEE is
On Thu, May 8, 2008 at 12:39 PM, Anne Archibald [EMAIL PROTECTED]
wrote:
2008/5/8 Charles R Harris [EMAIL PROTECTED]:
David, what you are using is a log(log(x)) representation internally.
IEEE
is *not* linear, it is logarithmic.
As Robert Kern says, yes, this is exactly what the OP and
On Thu, May 8, 2008 at 2:12 PM, Charles R Harris
[EMAIL PROTECTED] wrote:
On Thu, May 8, 2008 at 11:46 AM, Anne Archibald [EMAIL PROTECTED]
wrote:
2008/5/8 Charles R Harris [EMAIL PROTECTED]:
On Thu, May 8, 2008 at 10:56 AM, Robert Kern [EMAIL PROTECTED]
wrote:
When you're running
On 5/8/08, Anne Archibald [EMAIL PROTECTED] wrote:
Is logarray really the way to handle it, though? it seems like you
could probably get away with providing a logsum ufunc that did the
right thing. I mean, what operations does one want to do on logarrays?
add - logsum
subtract - ?
multiply
On Thu, May 8, 2008 at 11:46 AM, Anne Archibald [EMAIL PROTECTED]
wrote:
2008/5/8 Charles R Harris [EMAIL PROTECTED]:
On Thu, May 8, 2008 at 10:56 AM, Robert Kern [EMAIL PROTECTED]
wrote:
When you're running an optimizer over a PDF, you will be stuck in the
region of exp(-1000) for
2008/5/8 T J [EMAIL PROTECTED]:
On 5/8/08, Anne Archibald [EMAIL PROTECTED] wrote:
Is logarray really the way to handle it, though? it seems like you
could probably get away with providing a logsum ufunc that did the
right thing. I mean, what operations does one want to do on logarrays?
On Thu, 8 May 2008, Charles R Harris wrote:
On Thu, May 8, 2008 at 11:46 AM, Anne Archibald [EMAIL PROTECTED]
wrote:
2008/5/8 Charles R Harris [EMAIL PROTECTED]:
On Thu, May 8, 2008 at 10:56 AM, Robert Kern [EMAIL PROTECTED]
wrote:
When you're running an optimizer over a PDF, you will
On Thu, May 8, 2008 at 2:37 PM, Warren Focke [EMAIL PROTECTED]
wrote:
On Thu, 8 May 2008, Charles R Harris wrote:
On Thu, May 8, 2008 at 11:46 AM, Anne Archibald
[EMAIL PROTECTED]
wrote:
2008/5/8 Charles R Harris [EMAIL PROTECTED]:
On Thu, May 8, 2008 at 10:56 AM, Robert Kern
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