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23h
revised What is the $\lor$ symbol?
added table and further explanations
1d
revised What is the $\lor$ symbol?
added expalanation to convince the downvoter
1d
answered What is the $\lor$ symbol?
1d
answered Simple minimization problem
Jul
18
awarded  Good Answer
Jul
16
comment Interview riddle
@Awal: Developers often skip l and o to avoid confusions. Now, I seem to have confused you?
Jul
15
awarded  Nice Answer
Jul
15
comment Interview riddle
You mean $\frac{181 a ^{4} b ^{4} - 4318 a ^{4} b ^{3} + 37880 a ^{4} b ^{2} - 144623 a ^{4} b + 202440 a ^{4} + -3594 a ^{3} b ^{4} + 85893 a ^{3} b ^{3} - 754833 a ^{3} b ^{2} + 2886774 a ^{3} b - 4047120 a ^{3} + 26012 a ^{2} b ^{4} - 622766 a ^{2} b ^{3} + 5482627 a ^{2} b ^{2} - 21003793 a ^{2} b + 29493240 a ^{2} + -81093 a b ^{4} + 1944783 a b ^{3} - 17150580 a b ^{2} + 65813730 a b - 92559600 a + 91560 b ^{4} - 2199120 b ^{3} + 19423320 b ^{2} - 74648280 b + 105134400}{36} $?
Jul
14
answered Interview riddle
Jul
8
comment What kind of a matrix transformation is this?
Is your intended expression $\begin{pmatrix} 1 & 1 \\0&1\over{y}\end{pmatrix}*\begin{pmatrix}x & y\end{pmatrix}^T$? That would just result in $\begin{pmatrix} x + y \\ 1 \end{pmatrix}$.
Jun
29
comment A function on sets which is constant for all permutations
The problem is from IZO 2014, Day 2: artofproblemsolving.com/Forum/…
Jun
21
comment How to distribute 5-digit numbers in 5x5 matrices
Any solution to your problem can be transformed into other solutions by permuting the matrices. Therefore, by enforcing a sorted order of matrices, you can rule out many potential solutions and thus focus your search process.
Jun
21
comment How to distribute 5-digit numbers in 5x5 matrices
To reduce the search space you could introduce a symmetry breaking constraint: Matrix $m$ has to be smaller than matrix $m+1$. To compare two matrices, you could compare the smallest numbers contained in each of them.
Jun
20
comment Linearization of a product of two decision variables
And things don't improve if you make use of the bounds?
Jun
20
answered Linearization of a product of two decision variables
Jun
19
comment Linearization of a product of two decision variables
Are your decision variables of any specific type (continuous, integer, binary)? Do they have upper and/or lower bounds?
Jun
12
comment Simplify Boolean equations
It is the same solution as derived by jdc.
Jun
11
comment Simplify Boolean equations
wolframalpha.com comes up with a different result for F1. F2 and F3 are looking ok.
Jun
8
comment $2\times2$ matrices are not big enough
@bubba: yes, you have a point there. It requires rather high matrix dimensions to beat the classical matrix multiplication method by a Strassen-style method. But memory and cache tuning are restricted to linear acceleration factors, while it would lead to an exponential speedup, if we could multiply - for example - two $3\times3$ matrices with 21 or fewer elementary products. Apart from that: Research in the area of matrix multiplication has indeed created quite a few theoretical insights.
May
26
comment Covering one square by three smaller squares
Using a numerical solver and David's approach, I got 0.98268919 as minimum size for the small squares.