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136 lines
8.0 KiB
Matlab
136 lines
8.0 KiB
Matlab
% linesearch routine (does not use the gradient)
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%
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% [x,f,a,flg] = linesearch(func,x0,f0,df0,dx,a,varargin)
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%
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% func = string name of objective function
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% x0 = starting point of search
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% f0 = objective function at x0
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% df0 = derivative of objective function along dx at x0
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% dx = direction of linesearch
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% a = steplength input as guess output as taken
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% x = final point of search
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% f = objective function at final point
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% flg = indicates how step was determined (0 for Armijo step, 1 for
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% bracketing and refining a minimum)
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% Academic License Agreement
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%
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% Source Code
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%
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% Introduction
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% • This license agreement sets forth the terms and conditions under which the PAUL SCHERRER INSTITUT (PSI), CH-5232 Villigen-PSI, Switzerland (hereafter "LICENSOR")
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% will grant you (hereafter "LICENSEE") a royalty-free, non-exclusive license for academic, non-commercial purposes only (hereafter "LICENSE") to use the cSAXS
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% ptychography MATLAB package computer software program and associated documentation furnished hereunder (hereafter "PROGRAM").
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%
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% Terms and Conditions of the LICENSE
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% 1. LICENSOR grants to LICENSEE a royalty-free, non-exclusive license to use the PROGRAM for academic, non-commercial purposes, upon the terms and conditions
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% hereinafter set out and until termination of this license as set forth below.
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% 2. LICENSEE acknowledges that the PROGRAM is a research tool still in the development stage. The PROGRAM is provided without any related services, improvements
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% or warranties from LICENSOR and that the LICENSE is entered into in order to enable others to utilize the PROGRAM in their academic activities. It is the
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% LICENSEE’s responsibility to ensure its proper use and the correctness of the results.”
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% 3. THE PROGRAM IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR
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% A PARTICULAR PURPOSE AND NONINFRINGEMENT OF ANY PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS. IN NO EVENT SHALL THE LICENSOR, THE AUTHORS OR THE COPYRIGHT
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% HOLDERS BE LIABLE FOR ANY CLAIM, DIRECT, INDIRECT OR CONSEQUENTIAL DAMAGES OR OTHER LIABILITY ARISING FROM, OUT OF OR IN CONNECTION WITH THE PROGRAM OR THE USE
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% OF THE PROGRAM OR OTHER DEALINGS IN THE PROGRAM.
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% 4. LICENSEE agrees that it will use the PROGRAM and any modifications, improvements, or derivatives of PROGRAM that LICENSEE may create (collectively,
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% "IMPROVEMENTS") solely for academic, non-commercial purposes and that any copy of PROGRAM or derivatives thereof shall be distributed only under the same
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% license as PROGRAM. The terms "academic, non-commercial", as used in this Agreement, mean academic or other scholarly research which (a) is not undertaken for
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% profit, or (b) is not intended to produce works, services, or data for commercial use, or (c) is neither conducted, nor funded, by a person or an entity engaged
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% in the commercial use, application or exploitation of works similar to the PROGRAM.
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% 5. LICENSEE agrees that it shall make the following acknowledgement in any publication resulting from the use of the PROGRAM or any translation of the code into
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% another computing language:
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% "Data processing was carried out using the cSAXS ptychography MATLAB package developed by the Science IT and the coherent X-ray scattering (CXS) groups, Paul
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% Scherrer Institut, Switzerland."
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%
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% Additionally, any publication using the package, or any translation of the code into another computing language should cite for difference map:
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% P. Thibault, M. Dierolf, A. Menzel, O. Bunk, C. David, F. Pfeiffer, High-resolution scanning X-ray diffraction microscopy, Science 321, 379–382 (2008).
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% (doi: 10.1126/science.1158573),
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% for maximum likelihood:
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% P. Thibault and M. Guizar-Sicairos, Maximum-likelihood refinement for coherent diffractive imaging, New J. Phys. 14, 063004 (2012).
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% (doi: 10.1088/1367-2630/14/6/063004),
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% for mixed coherent modes:
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% P. Thibault and A. Menzel, Reconstructing state mixtures from diffraction measurements, Nature 494, 68–71 (2013). (doi: 10.1038/nature11806),
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% and/or for multislice:
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% E. H. R. Tsai, I. Usov, A. Diaz, A. Menzel, and M. Guizar-Sicairos, X-ray ptychography with extended depth of field, Opt. Express 24, 29089–29108 (2016).
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% (doi: 10.1364/OE.24.029089).
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% 6. Except for the above-mentioned acknowledgment, LICENSEE shall not use the PROGRAM title or the names or logos of LICENSOR, nor any adaptation thereof, nor the
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% names of any of its employees or laboratories, in any advertising, promotional or sales material without prior written consent obtained from LICENSOR in each case.
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% 7. Ownership of all rights, including copyright in the PROGRAM and in any material associated therewith, shall at all times remain with LICENSOR, and LICENSEE
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% agrees to preserve same. LICENSEE agrees not to use any portion of the PROGRAM or of any IMPROVEMENTS in any machine-readable form outside the PROGRAM, nor to
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% make any copies except for its internal use, without prior written consent of LICENSOR. LICENSEE agrees to place the following copyright notice on any such copies:
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% © All rights reserved. PAUL SCHERRER INSTITUT, Switzerland, Laboratory for Macromolecules and Bioimaging, 2017.
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% 8. The LICENSE shall not be construed to confer any rights upon LICENSEE by implication or otherwise except as specifically set forth herein.
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% 9. DISCLAIMER: LICENSEE shall be aware that Phase Focus Limited of Sheffield, UK has an international portfolio of patents and pending applications which relate
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% to ptychography and that the PROGRAM may be capable of being used in circumstances which may fall within the claims of one or more of the Phase Focus patents,
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% in particular of patent with international application number PCT/GB2005/001464. The LICENSOR explicitly declares not to indemnify the users of the software
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% in case Phase Focus or any other third party will open a legal action against the LICENSEE due to the use of the program.
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% 10. This Agreement shall be governed by the material laws of Switzerland and any dispute arising out of this Agreement or use of the PROGRAM shall be brought before
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% the courts of Zürich, Switzerland.
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function [x,f,a,flg] = linesearch(func,x0,f0,df0,dx,a,varargin)
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% check if descent direction
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if df0>=0
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warning('linesearch called w/o descent direction')
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x = x0; f = f0; fcount = [0,0]; flg = 0;
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return
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end
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% first point
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a1 = 0; f1 = f0;
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% try initial steplength
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f = feval(func,x0+a*dx,varargin{:}); % no gradient returned
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% keep track of old values & hopefully bracket a minimum
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a2 = a; f2 = f;
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% make sure initial step is feasible
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while isinf(f)
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a2 = a;
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a = 0.25*a;
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f = feval(func,x0+a*dx,varargin{:});
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end
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% decide what to do next based on Armijo condition
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b = 0; % parameter in Armijo condition (>=0)
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% if f does not satisfy Armijo condition (steplength may be too
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% large) -> decrease steplength until Armijo is satisfied
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if f>f0+a*b*df0
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while f>f0+a*b*df0
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if isinf(f2)||(f<=f2)
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a2 = a; f2 = f;
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end
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a = 0.25*a; % decrease steplength
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f = feval(func,x0+a*dx,varargin{:});
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end
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end
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% arrive here with a1=a0=0 and f<f1 (at least)
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tmp = 1;
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while f2<=f % try doubling a2
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a2 = 2*a2;
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f2 = feval(func,x0+a2*dx,varargin{:});
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if f2<f
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a1 = a; f1 = f;
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a = a2; f = f2;
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end
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if tmp==5; break; else tmp = tmp+1; end
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end
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% case where we should have a bracket, but f2 is infinite
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while isinf(f2)
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% disp('should have a bracket but f2 is infinite')
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u = a+0.25*(a2-a); % point between a and a2
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fu = feval(func,x0+u*dx,varargin{:});
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if fu<f
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a1 = a; f1 = f;
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a = u; f = fu;
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else
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a2 = u; f2 = fu;
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end
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end
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% last steps
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if (f<f1)&&(f<f2)&&isfinite(f2) % bracketing successful -> refine minimum
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[a,f] = engines.ML.brent(func,x0,dx,a1,a,a2,f1,f,f2,varargin{:});
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flg = 1; % use conjugate gradient next loop
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else % bracketing unsuccessful -> stop
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flg = 0; % use steepest descent next loop
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end
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x = x0+a*dx;
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return
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end
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