# CURAND no longer makes CU Array for Complex Numbers

**URL:** <https://discourse.julialang.org/t/curand-no-longer-makes-cu-array-for-complex-numbers/108602>\
**Category:** GPU\
**Created:** [January 10, 2024, 1:04am UTC](https://discourse.julialang.org/t/curand-no-longer-makes-cu-array-for-complex-numbers/108602 "2024-01-10T01:04:52Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![Allan\_Baker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/allan_baker/32/42645_2.png) [@Allan\_Baker](https://discourse.julialang.org/u/Allan_Baker)\
**Post date:** [January 10, 2024, 1:04am UTC](https://discourse.julialang.org/t/curand-no-longer-makes-cu-array-for-complex-numbers/108602/1 "2024-01-10T01:04:52Z")

</div>

I feel I am doing something wrong. I’m not an expert in this GPU coding, so I was happy when I got this working maybe a year or two ago. I’m revisiting this code and it has stopped working.

I have a vector of complex numbers representing a RF signal. I need to add noise to that signal. I want it to work on the GPU. I am using CuArrays since I don’t understand the complexities of using a kernel and keeping the random number stream straight. It probably would be more efficient as a kernel though if I understood that, but I don’t think it matters for my problem.

I had some code that used to work when generating complex random numbers. I updated and now it doesn’t. Not sure when this stopped working, but I’d like to know the correct syntax.

I think you can see the general problem. The randn function does different things if the type is Float64 verses ComplexF64.

This code generates a CuArray if the type is real.

```jula
julia> Random.randn(CURAND.default_rng(),Float64,10)
10-element CuArray{Float64, 1, CUDA.Mem.DeviceBuffer}:
  0.49637250761721785
  1.1621209684440397
 -1.200133485055596
 -0.3641995814787512
 -3.159735223992887
  1.8079578340924842
  1.180847386516405
 -0.9288064979411169
 -0.21460057071319238
  2.07001090351318

```

While the complexF64 version generates a vector instead of a CuArray. This causes my code to get upset since it expects a CuArray to be generated to add to operate on the CuArray that was passed in. To fix it seems like a mess since I want the same code to work with CPU or GPU as the RNG gets passed in.

```julia
julia> Random.randn(CURAND.default_rng(),ComplexF64,10)
10-element Vector{ComplexF64}:
   0.7718688832969476 + 0.7867351684604367im
  -0.4562811724789016 - 1.3444512656128818im
  -1.2646604765663483 + 0.7447540921496932im
  -0.7259376389798406 - 0.0653711465093766im
   0.4698858817529208 + 0.5430800530014905im
   0.9838594906913766 + 1.203688870480887im
 -0.19137495196505339 - 0.5837290641882306im
  0.19036064921205195 + 0.12221062922729947im
  -0.9799564403417708 + 1.1659964057563248im
  0.40613987626465775 + 0.4489427349696575im

```

Is this a bug? To be fair, the old syntax that worked used CUDA instead of CURAND. I’m not sure if that gets back to how old it might have been. I lost track. I could try to hunt it down if it is important.

> julia\> versioninfo()  
> Julia Version 1.9.2  
> Commit e4ee485e90 (2023-07-05 09:39 UTC)  
> Platform Info:  
> OS: Windows (x86\_64-w64-mingw32)  
> CPU: 12 × Intel(R) Core™ i7-10850H CPU @ 2.70GHz  
> WORD\_SIZE: 64  
> LIBM: libopenlibm  
> LLVM: libLLVM-14.0.6 (ORCJIT, skylake)  
> Threads: 16 on 12 virtual cores  
> Environment:  
> JULIA\_DIR = C:\Users\username\AppData\Local\Programs\Julia-1.9.2  
> JULIA\_PKG\_DEVDIR = D:\JULIA\DEVELOPMENT  
> JULIA\_PKG\_USE\_CLI\_GIT = true  
> JULIA\_SSL\_CA\_ROOTS\_PATH =  
> JULIA\_EDITOR = code  
> JULIA\_NUM\_THREADS =
> 
> [621f4979] AbstractFFTs v1.5.0  
> ⌅ [79e6a3ab] Adapt v3.7.1  
> ⌃ [4c88cf16] Aqua v0.7.4  
> [8b73e784] ArtifactUtils v0.2.4  
> ⌃ [6e4b80f9] BenchmarkTools v1.3.2  
> ⌃ [052768ef] CUDA v5.1.0  
> [35d6a980] ColorSchemes v3.24.0  
> [a80b9123] CommonMark v0.8.12  
> ⌃ [f68482b8] Cthulhu v2.9.6  
> [717857b8] DSP v0.7.9  
> [8bb1440f] DelimitedFiles v1.9.1  
> ⌃ [aae7a2af] DiffEqFlux v2.4.0  
> ⌃ [0c46a032] DifferentialEquations v7.10.0  
> [58007942] EulerYPRType v0.3.2  
> ⌃ [7a1cc6ca] FFTW v1.7.1  
> ⌃ [5789e2e9] FileIO v1.16.1  
> ⌃ [587475ba] Flux v0.14.6  
> ⌃ [0337cf30] GRUtils v0.8.3  
> [5c1252a2] GeometryBasics v0.4.9  
> [6218d12a] ImageMagick v1.3.0  
> [916415d5] Images v0.26.0  
> ⌅ [a98d9a8b] Interpolations v0.14.7  
> [3bf4e53f] LMQuaternions v0.6.5  
> [726dbf0d] LicenseCheck v0.2.2  
> [093fc24a] LightGraphs v1.3.5  
> [23992714] MAT v0.10.6  
> ⌃ [ee78f7c6] Makie v0.19.12  
> ⌅ [20f20a25] MakieCore v0.6.9  
> [777085ab] Mat3s v0.2.0  
> [7269a6da] MeshIO v0.4.10  
> ⌃ [961ee093] ModelingToolkit v8.70.0  
> [510215fc] Observables v0.5.5  
> ⌃ [6fe1bfb0] OffsetArrays v1.12.10  
> ⌅ [1dea7af3] OrdinaryDiffEq v6.58.2  
> ⌃ [e713c705] PackageAnalyzer v3.0.1  
> [f0f68f2c] PlotlyJS v0.18.11  
> [91a5bcdd] Plots v1.39.0  
> ⌃ [c3e4b0f8] Pluto v0.19.32  
> ⌃ [7f904dfe] PlutoUI v0.7.53  
> [3cdcf5f2] RecipesBase v1.3.4  
> ⌅ [731186ca] RecursiveArrayTools v2.38.10  
> ⌃ [295af30f] Revise v3.5.8  
> ⌃ [1ed8b502] SciMLSensitivity v7.47.0  
> [00bb0486] StandardAerospace v0.3.1  
> ⌃ [90137ffa] StaticArrays v1.6.5  
> ⌅ [0c5d862f] Symbolics v5.10.0  
> ⌃ [e88e6eb3] Zygote v0.6.67  
> [81553e4a] rfEnviroSim v0.3.6 `..`  
> [7e2434f1] xyzVector v0.6.2  
> [37e2e46d] LinearAlgebra  
> [44cfe95a] Pkg v1.9.2  
> [9a3f8284] Random  
> [10745b16] Statistics v1.9.0

---

<div class="post-metadata">

**Author:** ![maleadt](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/maleadt/32/10097_2.png) [@maleadt](https://discourse.julialang.org/u/maleadt)\
**Post date:** [January 10, 2024, 9:05am UTC](https://discourse.julialang.org/t/curand-no-longer-makes-cu-array-for-complex-numbers/108602/2 "2024-01-10T09:05:22Z")

</div>

> [@Allan\_Baker](#):
>
> `Random.randn(CURAND.default_rng(),ComplexF64,10)`

CURAND doesn’t support ComplexF64. Use `CUDA.default_rng()` for the native RNG, or even better, use `rand!` on a `CuArray{ComplexF64}` to auto-select an appropriate RNG.

---

<div class="post-metadata">

**Author:** ![Allan\_Baker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/allan_baker/32/42645_2.png) [@Allan\_Baker](https://discourse.julialang.org/u/Allan_Baker)\
**Post date:** [January 10, 2024, 1:34pm UTC](https://discourse.julialang.org/t/curand-no-longer-makes-cu-array-for-complex-numbers/108602/3 "2024-01-10T13:34:07Z")

</div>

> [@maleadt](#):
>
> appropriate

Hmm. I just changed it to CURAND because I thought that had replaced CUDA based on some of the documentation I saw to make things more generic across different GPU systems. Is there a good book or other resources that helps me get up to speed in taking designs to the GPU using Julia? I feel I’m leaving a lot of efficiency on the table.

---

<div class="post-metadata">

**Author:** ![Allan\_Baker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/allan_baker/32/42645_2.png) [@Allan\_Baker](https://discourse.julialang.org/u/Allan_Baker)\
**Post date:** [January 10, 2024, 1:39pm UTC](https://discourse.julialang.org/t/curand-no-longer-makes-cu-array-for-complex-numbers/108602/4 "2024-01-10T13:39:25Z")

</div>

I was trying to fix this problem by going to CURAND.

```julia
julia> Random.randn(CUDA.default_rng(),ComplexF64)
ERROR: MethodError: randn(::CUDA.RNG, ::Type{ComplexF64}) is ambiguous.

```

It used to work.

---

<div class="post-metadata">

**Author:** ![maleadt](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/maleadt/32/10097_2.png) [@maleadt](https://discourse.julialang.org/u/maleadt)\
**Post date:** [January 10, 2024, 4:57pm UTC](https://discourse.julialang.org/t/curand-no-longer-makes-cu-array-for-complex-numbers/108602/5 "2024-01-10T16:57:18Z")

</div>

> [@Allan\_Baker](#):
>
> I just changed it to CURAND because I thought that had replaced CUDA based on some of the documentation I saw to make things more generic across different GPU systems.

I’m not sure what you mean by that. By hard-coding `CURAND.default_rng()`, or even `CUDA.default_rng()`, you’re essentially locking your code to CUDA.jl, or even more specifically CURAND. Instead, it’s better to try and write generic array code that takes arbitrary inputs, and here calls `rand!` on them.

---

<div class="post-metadata">

**Author:** ![maleadt](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/maleadt/32/10097_2.png) [@maleadt](https://discourse.julialang.org/u/maleadt)\
**Post date:** [January 10, 2024, 4:58pm UTC](https://discourse.julialang.org/t/curand-no-longer-makes-cu-array-for-complex-numbers/108602/6 "2024-01-10T16:58:12Z")

</div>

I agree that shouldn’t error, but that isn’t something you want to do anyway, because you’re asking for a single element there. If you add dimensions, those calls aren’t ambiguous.

---

<div class="post-metadata">

**Author:** ![Allan\_Baker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/allan_baker/32/42645_2.png) [@Allan\_Baker](https://discourse.julialang.org/u/Allan_Baker)\
**Post date:** [January 11, 2024, 5:13pm UTC](https://discourse.julialang.org/t/curand-no-longer-makes-cu-array-for-complex-numbers/108602/7 "2024-01-11T17:13:33Z")

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Thank you for the excellent help. I got it working by using the randn! function and passing in the RNG with an existing CUArray which could be reused by the function.