- General
-
Идеи
Overload element-wise operators
I think element-wise operators need overloaded. Here is an example of why. With double precision in MATLAB, this works. I think it should work for the mp data type too.
>> x = 1:10, y = (11:20)'
x =
1 2 3 4 5 6 7 8 9 10
y =
11
12
13
14
15
16
17
18
19
20
>> A = x.*y
A =
11 22 33 44 55 66 77 88 99 110
12 24 36 48 60 72 84 96 108 120
13 26 39 52 65 78 91 104 117 130
14 28 42 56 70 84 98 112 126 140
15 30 45 60 75 90 105 120 135 150
16 32 48 64 80 96 112 128 144 160
17 34 51 68 85 102 119 136 153 170
18 36 54 72 90 108 126 144 162 180
19 38 57 76 95 114 133 152 171 190
20 40 60 80 100 120 140 160 180 200
>> A = mp(x).*mp(y)
Error using .* (line 1644)
Matrix dimensions must agree
Сервис поддержки клиентов работает на платформе UserEcho
Dear Jason,
Toolbox already overloads all element-wise operations. Moreover, the error message is perfectly valid, as arrays have incompatible dimensions - in fact, all MATLABs up to 2016a return the same error message for this operation.
However a year ago (starting from R2016b), MATLAB developers added "implicit arithmetic expansion" to make this kind of operations valid [1].
IMHO the feature is questionable, as it could break old code (e.g. see [2]) and it makes new code incompatible with older MATLABs.
This feature is not implemented in toolbox for the time being, please use classic MATLAB's techniques.
For example, A = bsxfun(@times,x,y) does exactly this.
[1] https://blogs.mathworks.com/loren/2016/10/24/matlab-arithmetic-expands-in-r2016b/
[2] http://undocumentedmatlab.com/blog/afterthoughts-on-implicit-expansion
What you are saying about change to implicit-expansion makes sense. I can accept that.
I did try bsxfun already. For some reason it seemed to be slower than just using a for loop.
FOR LOOP Construction:
A = nan(size(u,1), size(exponent,1));
for i = 1:n
A(:,i) = u(:,1).^(exponents(i,1));
end
bsxfun Construction:
A = bsxfun(@power, u(:,1), exponents(:,1)');
Majority of toolbox functions are implemented in C/C++ for the sake of speed.
But "bsxfun" is one of the functions we implement using M-language.
It has quite convoluted structure to cover many different use cases = extra overhead.
Manually coded special cases (like yours) are faster thanks to minimal overhead - all operations in this expression are implemented directly in toolbox core in C/C++ with optimizations for CPU cache, etc.
This functionality is available in newest toolbox version - 4.6.0.