# Latest

**URL:** https://discourse.julialang.org/latest.md?page=1531

[Latest](https://discourse.julialang.org/latest.md) · [Categories](https://discourse.julialang.org/categories.md) · [Tags](https://discourse.julialang.org/tags.md)

**Page:** 1532

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## [RNN Not learning](https://discourse.julialang.org/t/rnn-not-learning/51686)

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**Author:** [@Emilio4d46](https://discourse.julialang.org/u/Emilio4d46)\
**Replies:** 9\
**Last updated:** [January 4, 2021, 9:46am UTC](https://discourse.julialang.org/t/rnn-not-learning/51686 "2021-01-04T09:46:32Z")

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I have been trying to build an RNN in Julia using Flux and it does not seem to converge or learn at all. The code is learning on a parsed Stanford Sentiment Treebank (i.e. An array of words and a sentiment score) Th…

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## [Ghost function surviving between package versions](https://discourse.julialang.org/t/ghost-function-surviving-between-package-versions/52812)

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**Author:** [@virgile-baudrot](https://discourse.julialang.org/u/virgile-baudrot)\
**Replies:** 2\
**Last updated:** [January 4, 2021, 9:46am UTC](https://discourse.julialang.org/t/ghost-function-surviving-between-package-versions/52812 "2021-01-04T09:46:32Z")

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Dear all, I made a package with a function called runMCMC returning a DataFrame in version 0.2.0 and an Array in version 0.3.0 (ok, I should have upgrade to 1.0.0 but it’s quite confidential for now). I send 0.2.0 to …

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## [@NLconstraint with a sum, array and scalar variables](https://discourse.julialang.org/t/nlconstraint-with-a-sum-array-and-scalar-variables/52710)

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**Author:** [@maajdl](https://discourse.julialang.org/u/maajdl)\
**Replies:** 5\
**Last updated:** [January 4, 2021, 8:47am UTC](https://discourse.julialang.org/t/nlconstraint-with-a-sum-array-and-scalar-variables/52710 "2021-01-04T08:47:18Z")

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Hello and happy new year! Below is a toy problem. It deals with a mix of 4 chemicals. The quantities of the chemicals are given in the array xs. The temperature of the mix is the only unknow, subject to the constrai…

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## [Meaning of Δ in different \`apply!\` methods is different in different Flux optimizers?](https://discourse.julialang.org/t/meaning-of-in-different-apply-methods-is-different-in-different-flux-optimizers/52811)

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**Author:** [@gxyd](https://discourse.julialang.org/u/gxyd)\
**Replies:** 0\
**Last updated:** [January 4, 2021, 7:57am UTC](https://discourse.julialang.org/t/meaning-of-in-different-apply-methods-is-different-in-different-flux-optimizers/52811 "2021-01-04T07:57:08Z")

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Hi, I want to understand the meaning of Δ used in different methods (i.e. for different optimizers) in Flux. For example: in Descent, the meaning of Δ seems to be: \[∂f/∂θᵢ\] i=1,2,3,… While looking at the meaning of Δ …

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## [Map Performance with CuArrays](https://discourse.julialang.org/t/map-performance-with-cuarrays/33497)

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**Author:** [@bmit](https://discourse.julialang.org/u/bmit)\
**Replies:** 15\
**Last updated:** [January 4, 2021, 7:29am UTC](https://discourse.julialang.org/t/map-performance-with-cuarrays/33497 "2021-01-04T07:29:48Z")

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I’m trying to benchmark different methods of calling the same in-place function on subsets of a large data block using CuArrays. I’m using fft as an example function because I can baseline against planning an fft over on…

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## [Sum is very slow (and I can't figure out why)](https://discourse.julialang.org/t/sum-is-very-slow-and-i-cant-figure-out-why/52791)

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**Author:** [@Ferran\_Mazzanti](https://discourse.julialang.org/u/Ferran_Mazzanti)\
**Replies:** 4\
**Last updated:** [January 4, 2021, 7:25am UTC](https://discourse.julialang.org/t/sum-is-very-slow-and-i-cant-figure-out-why/52791 "2021-01-04T07:25:42Z")

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Hi, I’m building up a Monte Carlo code in CUDA that, as intermediate steps, needs to perform sums of several thousand Floats. The fact is that the numbers are produced by a function V(r,dip) where r is vector of floats …

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## [CUDA does not successfully initialise](https://discourse.julialang.org/t/cuda-does-not-successfully-initialise/52661)

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**Author:** [@iHany](https://discourse.julialang.org/u/iHany)\
**Replies:** 2\
**Last updated:** [January 4, 2021, 7:20am UTC](https://discourse.julialang.org/t/cuda-does-not-successfully-initialise/52661 "2021-01-04T07:20:24Z")

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I installed CUDA by \]add CUDA and tried to test it by test CUDA. However, I encountered the below error message. CUDA initialisation error ERROR: LoadError: CUDA.jl did not successfully initialize, and is not usable. I…

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## [Python does not have if statements](https://discourse.julialang.org/t/python-does-not-have-if-statements/52765)

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**Author:** [@johnh](https://discourse.julialang.org/u/johnh)\
**Replies:** 13\
**Last updated:** [January 4, 2021, 6:20am UTC](https://discourse.julialang.org/t/python-does-not-have-if-statements/52765 "2021-01-04T06:20:34Z")

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Yes of course i does. Please look at the interesting tweet below. Julia has the Bool type of course. But when I did a little digging I find that Bool takes up 8 bits - I guess that does not really matter on modern compu…

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## [WGLMakie meshscatter plot GPU load goes to 70% and stays there](https://discourse.julialang.org/t/wglmakie-meshscatter-plot-gpu-load-goes-to-70-and-stays-there/52810)

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**Author:** [@woolstar](https://discourse.julialang.org/u/woolstar)\
**Replies:** 0\
**Last updated:** [January 4, 2021, 5:52am UTC](https://discourse.julialang.org/t/wglmakie-meshscatter-plot-gpu-load-goes-to-70-and-stays-there/52810 "2021-01-04T05:52:05Z")

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I am doing some 3D plotting in Makie (using WGLMakie in Pluto), and even when not changing the scene, the load on my graphics card goes to about 70% and stays there, as if it is continually redrawing the scene. Is there…

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## [How Does a beginner start with making a website in Julia](https://discourse.julialang.org/t/how-does-a-beginner-start-with-making-a-website-in-julia/52808)

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**Author:** [@Nitish\_Dubey](https://discourse.julialang.org/u/Nitish_Dubey)\
**Replies:** 2\
**Last updated:** [January 4, 2021, 5:34am UTC](https://discourse.julialang.org/t/how-does-a-beginner-start-with-making-a-website-in-julia/52808 "2021-01-04T05:34:12Z")

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Hi, I am a Maths student and the only languages I know are C and Julia and I want to build a website of my own in Julia. and i have no prior experience with web development. How does one start with it ?

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## [Sending functions within structs to workers leads to world age problem](https://discourse.julialang.org/t/sending-functions-within-structs-to-workers-leads-to-world-age-problem/52717)

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**Author:** [@vancleve](https://discourse.julialang.org/u/vancleve)\
**Replies:** 4\
**Last updated:** [January 4, 2021, 3:34am UTC](https://discourse.julialang.org/t/sending-functions-within-structs-to-workers-leads-to-world-age-problem/52717 "2021-01-04T03:34:25Z")

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I have a simulation where I pass functions as parameters by putting them in a parameter object. However, when I try to run the simulation using Distributed, the functions do not run in the workers due to their world age …

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## [How to check if a condition is true for only one element in an array](https://discourse.julialang.org/t/how-to-check-if-a-condition-is-true-for-only-one-element-in-an-array/52764)

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**Author:** [@StevenSiew](https://discourse.julialang.org/u/StevenSiew)\
**Replies:** 4\
**Last updated:** [January 4, 2021, 1:11am UTC](https://discourse.julialang.org/t/how-to-check-if-a-condition-is-true-for-only-one-element-in-an-array/52764 "2021-01-04T01:11:28Z")

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I can do the following julia\> array = \[1,3,4,7,9\]; julia\> All\_numbers\_are\_positive = all(x-\>x\>0,array) true julia\> At\_least\_one\_number\_is\_even = any(iseven,array) true But how do I do Only\_one\_number\_is\_even ?

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## [Geospatial developer jobs twitter](https://discourse.julialang.org/t/geospatial-developer-jobs-twitter/52766)

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**Author:** [@johnh](https://discourse.julialang.org/u/johnh)\
**Replies:** 3\
**Last updated:** [January 3, 2021, 10:44pm UTC](https://discourse.julialang.org/t/geospatial-developer-jobs-twitter/52766 "2021-01-03T22:44:07Z")

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A new Twitter account posting geospatial developer jobs https://twitter.com/DevjobsGeo

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## [\`let\` syntax weirdness](https://discourse.julialang.org/t/let-syntax-weirdness/52738)

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**Author:** [@cscherrer](https://discourse.julialang.org/u/cscherrer)\
**Replies:** 38\
**Last updated:** [January 3, 2021, 10:20pm UTC](https://discourse.julialang.org/t/let-syntax-weirdness/52738 "2021-01-03T22:20:43Z")

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let is great and very important to have, but the syntax is very unusual. Before running them, try to guess what these do: function f1() a = 1 b = 2 c = let a = 3 b = 4 a+b end (a,b,…

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## [Create a simple CUDA.sum kernel](https://discourse.julialang.org/t/create-a-simple-cuda-sum-kernel/52797)

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**Author:** [@Ferran\_Mazzanti](https://discourse.julialang.org/u/Ferran_Mazzanti)\
**Replies:** 3\
**Last updated:** [January 3, 2021, 10:09pm UTC](https://discourse.julialang.org/t/create-a-simple-cuda-sum-kernel/52797 "2021-01-03T22:09:23Z")

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Hi again, as you can see, I’m trying to understand some basic CUDA kernel programming under julia, so please try not to be too rough with me… :slight\_smile: This time I want to build up a kernel that takes a bunch of …

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## [Type stability when DataType is passed as a keyword argument](https://discourse.julialang.org/t/type-stability-when-datatype-is-passed-as-a-keyword-argument/52770)

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**Author:** [@Christopher\_Fisher](https://discourse.julialang.org/u/Christopher_Fisher)\
**Replies:** 3\
**Last updated:** [January 3, 2021, 8:57pm UTC](https://discourse.julialang.org/t/type-stability-when-datatype-is-passed-as-a-keyword-argument/52770 "2021-01-03T20:57:56Z")

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Hi all- I have a question about type stability when a DataType is passed as a keyword argument. The code below shows all combinations of positional vs keyword arguments and Float64 vs DataType. Why is the DataType keywo…

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## [Options for developing GUI standalone app](https://discourse.julialang.org/t/options-for-developing-gui-standalone-app/52776)

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**Author:** [@dlakelan](https://discourse.julialang.org/u/dlakelan)\
**Replies:** 8\
**Last updated:** [January 3, 2021, 8:40pm UTC](https://discourse.julialang.org/t/options-for-developing-gui-standalone-app/52776 "2021-01-03T20:40:20Z")

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A lot of what I’ve used Julia for so far has been data analysis with Jupiter or Pluto, or writing command line scripts. Now I want to develop a tool for measuring network performance under various conditions. It should h…

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## [Defining Sparse Matrix from Scratch using vectors](https://discourse.julialang.org/t/defining-sparse-matrix-from-scratch-using-vectors/52772)

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**Author:** [@tgautam03](https://discourse.julialang.org/u/tgautam03)\
**Replies:** 6\
**Last updated:** [January 3, 2021, 6:56pm UTC](https://discourse.julialang.org/t/defining-sparse-matrix-from-scratch-using-vectors/52772 "2021-01-03T18:56:45Z")

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Hi I want to create a custom tridiagonal matrix type whose inputs will be 3 different vectors (c, d and e). These 3 vectors will make the matrix in a format as follows: I tried writing a struct struct tridiag \<: …

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## [Working implementation of MAML (meta-learning) for FluxML?](https://discourse.julialang.org/t/working-implementation-of-maml-meta-learning-for-fluxml/51954)

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**Author:** [@bad\_at\_math](https://discourse.julialang.org/u/bad_at_math)\
**Replies:** 1\
**Last updated:** [January 3, 2021, 5:37pm UTC](https://discourse.julialang.org/t/working-implementation-of-maml-meta-learning-for-fluxml/51954 "2021-01-03T17:37:24Z")

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Hi everyone, I was wondering if there are any public implementations of meta-learning techniques such as MAML (\[1703.03400\] Model-Agnostic Meta-Learning for Fast Adaptation of Deep Networks) in Flux. The model zoo has a…

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## [Macro to create structs with custom fields and parametric types](https://discourse.julialang.org/t/macro-to-create-structs-with-custom-fields-and-parametric-types/52781)

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**Author:** [@mrVeng](https://discourse.julialang.org/u/mrVeng)\
**Replies:** 0\
**Last updated:** [January 3, 2021, 4:59pm UTC](https://discourse.julialang.org/t/macro-to-create-structs-with-custom-fields-and-parametric-types/52781 "2021-01-03T16:59:36Z")

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Hi there, I am starting to learn about Macros in Julia and have a few difficulties with it. My goal is to create a new struct with some custom fields. After searching and reading here on discourse, I found this useful …

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## [Improvement for slicing 2d arrays?](https://discourse.julialang.org/t/improvement-for-slicing-2d-arrays/52775)

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**Author:** [@freeman](https://discourse.julialang.org/u/freeman)\
**Replies:** 2\
**Last updated:** [January 3, 2021, 3:41pm UTC](https://discourse.julialang.org/t/improvement-for-slicing-2d-arrays/52775 "2021-01-03T15:41:30Z")

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Consider the following 2d array: X = Array{Float64, 2}(undef, 4, 2) X\[:,1\] = \[1,NaN,3,4\] X\[:,2\] = \[2,3,4,5\] I want to filter out all rows which include at least one NaN. This could be done by instantiating a “mask” vec…

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## [DimensionMismatch("arrays could not be broadcast to a common size")](https://discourse.julialang.org/t/dimensionmismatch-arrays-could-not-be-broadcast-to-a-common-size/52696)

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**Author:** [@marouane1994](https://discourse.julialang.org/u/marouane1994)\
**Replies:** 8\
**Last updated:** [January 3, 2021, 3:32pm UTC](https://discourse.julialang.org/t/dimensionmismatch-arrays-could-not-be-broadcast-to-a-common-size/52696 "2021-01-03T15:32:21Z")

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i have this function for computing a probability function probability(eta,pdc,x::Array,y::Array) P=\[\] for k in 1:length(y) if y\[k\]==0 push!(P,(1-pdc)\*(1-eta\*(1-pdc))^x\[k\]) elseif y\[k\]…

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## [Parallel independent loops in julia](https://discourse.julialang.org/t/parallel-independent-loops-in-julia/52737)

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**Author:** [@Nishan](https://discourse.julialang.org/u/Nishan)\
**Replies:** 5\
**Last updated:** [January 3, 2021, 2:55pm UTC](https://discourse.julialang.org/t/parallel-independent-loops-in-julia/52737 "2021-01-03T14:55:07Z")

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Hello everyone, I am new to julia and currently I am converting my tensor networks codes from python to julia and till now it seems great and I could do it without much pain and just by rewriting it in julia I have gaine…

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## [Issues in assigning combinations to indices and appending values to arrays](https://discourse.julialang.org/t/issues-in-assigning-combinations-to-indices-and-appending-values-to-arrays/52771)

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**Author:** [@mdsa3d](https://discourse.julialang.org/u/mdsa3d)\
**Replies:** 1\
**Last updated:** [January 3, 2021, 1:23pm UTC](https://discourse.julialang.org/t/issues-in-assigning-combinations-to-indices-and-appending-values-to-arrays/52771 "2021-01-03T13:23:45Z")

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I would like to seek advice on this code snippet, results, xi, xj = (\[\] for count in 1:6) for comb in c i, j = comb #assign the rows of comb\[i\] to i and comb\[j\] to j result = algae(xi = df1\[:, i\], xj = df2\[:, j\],…

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## [What is the alternative to Python gym.spaces.Box() in Julia?](https://discourse.julialang.org/t/what-is-the-alternative-to-python-gym-spaces-box-in-julia/52758)

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**Author:** [@ZdM87](https://discourse.julialang.org/u/ZdM87)\
**Replies:** 2\
**Last updated:** [January 3, 2021, 12:52pm UTC](https://discourse.julialang.org/t/what-is-the-alternative-to-python-gym-spaces-box-in-julia/52758 "2021-01-03T12:52:06Z")

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In Python gym’s there is a class called Box that defines a (possibly unbounded) box in R^n. Is there any alternative to this box in Julia? There is IntervalSets.jl but I cannot seem to be able to create a Cartesian prod…

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## [\[ANN\] Standard Young tableaux](https://discourse.julialang.org/t/ann-standard-young-tableaux/52750)

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**Author:** [@stla](https://discourse.julialang.org/u/stla)\
**Replies:** 2\
**Last updated:** [January 3, 2021, 11:02am UTC](https://discourse.julialang.org/t/ann-standard-young-tableaux/52750 "2021-01-03T11:02:45Z")

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Hello, Some stuff for standard Young tableaux: stla.github.io/StandardYoungTableaux.jl. Cheers.

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## [ERROR: Output should be scalar; gradients are not defined for output](https://discourse.julialang.org/t/error-output-should-be-scalar-gradients-are-not-defined-for-output/52769)

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**Author:** [@BaoBaoDeMeng](https://discourse.julialang.org/u/BaoBaoDeMeng)\
**Replies:** 0\
**Last updated:** [January 3, 2021, 9:16am UTC](https://discourse.julialang.org/t/error-output-should-be-scalar-gradients-are-not-defined-for-output/52769 "2021-01-03T09:16:57Z")

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using Flux W\_1 = rand(2) W\_2 = rand(2) W\_3 = rand(2) b\_1 = rand(2) b\_2 = rand(1) function z(x,t) return (W\_1x+W\_2t+b\_1) end function sigmod(u) return 1/(1+exp(-u)) end function g\_u(x,t) return sum(\[sigmod(z…

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## [\[SOLVED\] Nothing returned in the Zygote derivative](https://discourse.julialang.org/t/solved-nothing-returned-in-the-zygote-derivative/52748)

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**Author:** [@sheevy](https://discourse.julialang.org/u/sheevy)\
**Replies:** 1\
**Last updated:** [January 2, 2021, 11:56pm UTC](https://discourse.julialang.org/t/solved-nothing-returned-in-the-zygote-derivative/52748 "2021-01-02T23:56:54Z")

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In my mind the following definitions are equivalent: function test\_working(x) return max(x - 1.0, 0.0) end function test\_not\_working(x) if x \> 1.0 return x - 1.0 else return 0.0 end end …

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## [Better Alternative to Eval? Building Browser based IDE for Julia](https://discourse.julialang.org/t/better-alternative-to-eval-building-browser-based-ide-for-julia/52155)

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**Author:** [@Joe\_Schnetzler](https://discourse.julialang.org/u/Joe_Schnetzler)\
**Replies:** 12\
**Last updated:** [January 2, 2021, 11:45am UTC](https://discourse.julialang.org/t/better-alternative-to-eval-building-browser-based-ide-for-julia/52155 "2021-01-02T11:45:09Z")

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Hello! After months of looking for and waiting for a quality cloud/browser-based IDE that fits my needs and wants for Julia, I have taken it upon myself to build my own. I come from a heavy statistics background so I am …

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## [Clang.jl wrapper generation warnings/missing parts](https://discourse.julialang.org/t/clang-jl-wrapper-generation-warnings-missing-parts/34093)

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**Author:** [@rayegun](https://discourse.julialang.org/u/rayegun)\
**Replies:** 9\
**Last updated:** [January 2, 2021, 10:29pm UTC](https://discourse.julialang.org/t/clang-jl-wrapper-generation-warnings-missing-parts/34093 "2021-01-02T22:29:25Z")

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I’m trying to wrap this this GraphBLAS.h file using Clang.jl (There is already a wrapper package, but I want to try generating it automatically). I used this code: const z = "/usr/lib/clang/9.0.0/include" const y = "/ho…

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