8.35.1 Top new questions this week

8.35.1.1 Fast Sparse Tensor Addition
8.35.1.2 A problem on the pattern (:) of Heads
8.35.1.3 Finite element method solution data, Mathematica 13.1
8.35.1.4 Still bug in Integrate
8.35.1.5 How to Specify Arrowhead Color
8.35.1.6 Animating a potential function (eigenfunctions of Laplace's equation) - something has changed
8.35.1.7 Sum indexed over set
8.35.1.1 Fast Sparse Tensor Addition

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=274994

How can one do a fast sparse tensor addition? 
Below, I have the following code: We first generate 3 random sparse 1000x1000x1000 tensors with 10^6 entries each. 
Then, I want to add them. But the usual ... 
[list-manipulation] [performance-tuning] [tensors] [sparse-arrays]
 
asked by Florentin Münch https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=88547 Score of 7
answered by Henrik Schumacher https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=38178 Score of 7
8.35.1.2 A problem on the pattern (:) of Heads

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=275078

I defined 
 Clear[f, g] 
f[(h : Exp | Log)[x_]] := x; 
g[(h : Log | Exp)[x_]] := x; 
 
The code gives a weird result: 
... 
[argument-patterns] [head]
 
asked by Curious Cat https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=88660 Score of 6
answered by lericr https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=84894 Score of 10
8.35.1.3 Finite element method solution data, Mathematica 13.1

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=275183

I just upgraded to Mathematica 13.1 and encountered the following issue (this is just code from the first few lines of the FEM programming documentation): 
... 
[differential-equations] [finite-element-method] [documentation]
 
asked by Will.Mo https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=49788 Score of 5
8.35.1.4 Still bug in Integrate

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=275120

Let us consider in version 13.1 on Windows 10 
 j = Integrate[2^(I*x)*Log[x]/x, {x, b, Infinity}] 
 
 
... 
[calculus-and-analysis] [bugs]
 
asked by user64494 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=7152 Score of 5
answered by Akku14 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=34287 Score of 5
8.35.1.5 How to Specify Arrowhead Color

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=275080

I've been researching this question on how best to specify just an arrowhead's color. I've tried a Graphics primitive but to no avail. I've written this code and would like to color just the ... 
[graphs-and-networks]
 
asked by PRG https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=42700 Score of 5
answered by swish https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=2490 Score of 7
8.35.1.6 Animating a potential function (eigenfunctions of Laplace's equation) - something has changed

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=275139

I had this working with Kuba's help some time ago see here but something has changed. I am using version 13.0. 
The animation lay out has changed to this configuration where the animation bar is ... 
[dynamic] [finite-element-method]
 
asked by Hugh https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=12558 Score of 4
answered by cvgmt https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=72111 Score of 2
8.35.1.7 Sum indexed over set

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=275209

Say I have  sets = {{a,b},{c,d},{e,f}}  and I want to compute a sum like  f[a,b] + f[c,d] + f[e,f] . One way to do this is to do 
<... 
[summation] [partitions]
 
asked by almostsurely https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=88700 Score of 4
answered by user293787 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=85954 Score of 7