New Sum of Powers Log Function
04-02-2021, 01:18 PM
Post: #22
 Albert Chan Senior Member Posts: 1,791 Joined: Jul 2018
RE: New Sum of Powers Log Function
(04-02-2021 01:29 AM)Albert Chan Wrote:  Note that guess is evaluated twice. This is a fluke of mpmath, to simplify code.
The branched solver(s) re-calculated from the same guess again.

This is the patch to fix this issue.
C:\python\Lib\site-packages\mpmath\calculus\optimization.py, findroot():

Right before entering solver, i.e. below comment "use solver"
Code:
        # use solver         f0, p = f, [tuple(x0), fx] # cache previous result         def f(*x):             if x!=p[0]: p[0]=x; p[1]=f0(*x)             return p[1]

What is shocking is the patch may save more than 1 call.
Example, copied from help(findroot):

>>> f = [lambda x1, x2: x1**2 + x2, lambda x1, x2: 5*x1**2 - 3*x1 + 2*x2 - 3]
>>> findroot(f, (0, 0))
[-0.618033988749895]
[-0.381966011250105]

Patched findroot reduced f calls, from 24, down to 17
Code:
01  0.0                0.0 02  1.45519152284e-11  0.0 03  0.0                1.45519152284e-11 04  -1.00000000001     1.45519152285e-11 05  -0.500000000005    7.27595761425e-12 06  -0.49999999999     7.27595761425e-12 07  -0.500000000005    2.18278728426e-11 08  -0.625             -0.374999999999 09  -0.624999999986    -0.374999999999 10  -0.625             -0.374999999985 11  -0.618055555556    -0.381944444445 12  -0.618055555541    -0.381944444445 13  -0.618055555556    -0.38194444443 14  -0.618033988958    -0.381966011042 15  -0.618033988943    -0.381966011042 16  -0.618033988958    -0.381966011028 17  -0.61803398875     -0.38196601125
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 Messages In This Thread New Sum of Powers Log Function - Namir - 03-29-2021, 04:53 PM RE: New Sum of Powers Log Function - C.Ret - 03-29-2021, 08:39 PM RE: New Sum of Powers Log Function - Albert Chan - 03-29-2021, 10:47 PM RE: New Sum of Powers Log Function - Albert Chan - 03-30-2021, 01:44 AM RE: New Sum of Powers Log Function - Albert Chan - 03-30-2021, 08:35 PM RE: New Sum of Powers Log Function - Albert Chan - 03-30-2021, 10:26 PM RE: New Sum of Powers Log Function - Namir - 03-30-2021, 11:05 AM RE: New Sum of Powers Log Function - Albert Chan - 03-30-2021, 04:35 PM RE: New Sum of Powers Log Function - Paul Dale - 03-30-2021, 11:41 AM RE: New Sum of Powers Log Function - Gene - 03-30-2021, 01:43 PM RE: New Sum of Powers Log Function - C.Ret - 03-30-2021, 04:01 PM RE: New Sum of Powers Log Function - Namir - 03-30-2021, 05:56 PM RE: New Sum of Powers Log Function - Namir - 03-31-2021, 01:27 PM RE: New Sum of Powers Log Function - Albert Chan - 03-31-2021, 04:06 PM RE: New Sum of Powers Log Function - Albert Chan - 03-31-2021, 09:25 PM RE: New Sum of Powers Log Function - Namir - 03-31-2021, 02:19 PM RE: New Sum of Powers Log Function - Albert Chan - 04-01-2021, 02:56 PM RE: New Sum of Powers Log Function - Namir - 04-01-2021, 06:05 PM RE: New Sum of Powers Log Function - Albert Chan - 04-01-2021, 11:05 PM RE: New Sum of Powers Log Function - Namir - 04-01-2021, 11:55 PM RE: New Sum of Powers Log Function - Albert Chan - 04-02-2021, 01:29 AM RE: New Sum of Powers Log Function - Albert Chan - 04-02-2021 01:18 PM RE: New Sum of Powers Log Function - Namir - 04-04-2021, 03:41 PM

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