My problem can be simply understand by the following case: when I write the following program, I hope that c=a[1:5]+b[1:3] a=[1 2 3 4 5] b=[1 2 3] c = 0 for i in 1:5, j in 1:3 c += a[i] + b[j] end but that is equal to a = [1 2 3 4 5] b = [1 2 3] c = 0 for i in 1:5 for j in 1:3 …

I think you want something along the lines of for v in [a, b] # iterate among the various "containers" for i in eachindex(v) # iterate along the indices of each container c += v[i] end end That being said, if you have a list of arrays, e.g. vs = [rand(100) for _ in 1:100], you coul…

[image] xspeng: c=a[1:5]+b[1:3] What exactly are you expecting? Here you are summing a vector of length 5 with another vector of length 3, it is not clear to me what you want as a result.

My fault, I just wnat to add each element of array a and arry b, here the example is too simple, actually, I also need to make some complex calculation for each element of array a and array b and then sum them togher with for loop

julia> some_complex_calculation(x) = x + sin(x) some_complex_calculation (generic function with 1 method) julia> a = [1,2,3,4,5]; b = [6,7,8,9,10]; # same length (and comas, if these are column-vectors) julia> c = some_complex_calculation.(a) .+ some_complex_calculation.(b) # note the dots 5-eleme…

Yeah, seems work, I will try, if I have more questions, will ask you again, thanks

My initial plan is doing this, but this will take on a lot of memory allocation, so I plan to use for loop to expand the equations, and add them with for loop and it works better, but now, I have to add two formulas with different array length together(add each element of each formulas together), it…

There one would only be allocating the output array c, which could be also preallocated and overwritten with c .= . And that would be equivalent to the loop, roughly. But anyway, I do not get exactly what you want, I’m happy others did. Good luck :slightly_smiling_face:

Maybe this example is more close to my question a=rand(5) b=rand(5) c=rand(5) d=rand(3) e=rand(3) y=dot(a,b.*exp(c.+2))+dot(d,e) # the initial formula which will cause a lot of memory allocation I just want to realize the same purpose with for loop, but a,b,c, is longer than d,e array, and I can…

Compute the dot(d,e) before the loop and add it as a scalar in the loop to each element. Ps. The allocations in your code are from the b.*exp(c.+2) expression, which generates a new array. It is fine to use a loop to solve that, and one-liners also are possible.

[image] xspeng: but now with dot(d,e) , how can I realize the same aim as this y=dot(a,b.*exp(c.+2))+dot(d,e) with for loop You can just have y = dot(d,e) before the loop, or y += dot(d,e) after. You want to iterate over these two things one after the other, that’s what the code with two dots…

Accumulation in the for loop

General Usage

xspeng January 21, 2022, 2:31pm 18

Hi, if you have time, could you please help me see another question about distributed problems, here is the link

Distributed solving ODEs problem

Topic		Replies	Views
Iterating over several arrays New to Julia	14	413	March 24, 2021
For loop optimization Performance performance , memory-allocation , loops	3	1705	October 31, 2021
Array cumulation General Usage array	4	505	December 23, 2020
Summing arrays efficiently Performance	9	8662	September 22, 2018
Reduce allocations in row-by-row dotproduct New to Julia	5	138	February 5, 2025

Accumulation in the for loop

Related topics