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Date	File	Comment by	Comment	Rating
21 Sep 2009	All Permutations of integers with sum criteria All Pernutations of integers with sum criteria Author: Bruno Luong	Petschel, Ben	Nice program. Users might also be interested in a looped solution using the function "nextwhile" in the NextVector toolbox <pre class="link">http://www.mathworks.com/matlabcentral/fileexchange/24757</pre>. If the entire matrix of combinations is needed then Bruno's version is faster (because row concatenation is slow) otherwise the looped solution is faster.
16 Sep 2009	Blendenpik A fast solver of dense rectangular dense linear equations . (least squares or underdetermined). Author: Haim Avron	Petschel, Ben	Nice work
14 Sep 2009	Blendenpik A fast solver of dense rectangular dense linear equations . (least squares or underdetermined). Author: Haim Avron	Petschel, Ben	This is potentially a novel and useful algorithm but I couldn't get it to install because it seems to require a separate installation of FFTW C libraries, even though FFTW already comes with MATLAB and is used by the built-in version of FFT. Also there is no mention of how the results compare in accuracy and speed against the built-in solves least-squares "\", so why go to the trouble of getting it to work?
11 Sep 2009	Blendenpik A fast solver of dense rectangular dense linear equations . (least squares or underdetermined). Author: Haim Avron	Petschel, Ben	Can you post the results of benchmarking against "\" please?
03 Sep 2009	setdiff Set difference of two sets of positive integers (much faster than built-in setdiff) Author: Nick	Petschel, Ben	Neat idea. How does the speed compare when you use sparse and/or logical arrays, e.g. to do setdiff([1,1e9],1) ?
31 Jul 2009	Fractions Toolbox create and manipulate fractions (K+N/D) using exact arithmetic Author: Ben Petschel	Petschel, Ben	Hi Khaled, thanks for pointing that out (I forgot to run "rehash path" when testing without the vpi toolbox). I've submitted an update which should become available soon. Let me know if you have any further problems.
14 Jul 2009	Variable Precision Integer Arithmetic Arithmetic with integers of fully arbitrary size. Arrays and vectors of vpi numbers are supported. Author: John D'Errico	Petschel, Ben	John, you've done a great service to the mathematical community (esp. number theorists and Project Euler enthusiasts!) In the vpi/add carry operation you could improve the performance of pathological cases such as 1+vpi(repmat('9',1,1e6)) by changing the while loop to a for loop.
21 Mar 2009	Count Loops in a Graph Calculates the number of loops in a graph consisting of nodes and edges Author: Joseph Kirk	Petschel, Ben	Nice code and very well documented. Another idea uses the theory of cycle subspaces (e.g. chapter 5 of Wallis's book on graph theory) - use a spanning tree to construct the (e-v+1) fundamental cycles and then check all 2^(e-v+1) combinations to eliminate disjoint unions and figure-8's. Does this algorithm compare favourably with your tree method?
18 Feb 2009	find_components finds the connected components of an image Author: Tim Davis	Petschel, Ben	Nice code Tim. I hadn't come across DMPERM before either. The variables K, East, South aren't really needed because K(E)=E, K(S)=S, East(E)=E+m, South(S)=S+1, and E & S can be defined without K.
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