# Random numbers in \[0.f0,1.f0\]
**URL:** https://discourse.julialang.org/t/random-numbers-in-0-f0-1-f0/30926
**Category:** GPU
**Created:** [November 10, 2019, 5:31pm UTC](https://discourse.julialang.org/t/random-numbers-in-0-f0-1-f0/30926 "2019-11-10T17:31:00Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Ferran\_Mazzanti](https://discourse.julialang.org/u/Ferran_Mazzanti)
#### Post date: [November 10, 2019, 5:31pm UTC](https://discourse.julialang.org/t/random-numbers-in-0-f0-1-f0/30926/1 "2019-11-10T17:31:00Z")
Hi again,
is there a simple way to have the same as this
```julia
rand([0.f0,1.f0],10)
```
on the GPU? I need to generate random bits (in that case they’re Float32 but anyway), and trying the obvious thing refuses to work
```julia
CuArrays.rand([0.f0,1.f0],10)
MethodError: no method matching rand(::Array{Float32,1}, ::Int64)
You may have intended to import Base.rand
Closest candidates are:
rand(!Matched::Union{Type{Float32}, Type{Float64}}, ::Integer, !Matched::Integer...) at /home/mazzanti/.julia/packages/CuArrays/wXQp8/src/rand/highlevel.jl:122
rand(!Matched::Type, ::Integer, !Matched::Integer...) at /home/mazzanti/.julia/packages/CuArrays/wXQp8/src/rand/highlevel.jl:147
rand(!Matched::Integer, ::Integer...) at /home/mazzanti/.julia/packages/CuArrays/wXQp8/src/rand/highlevel.jl:157
Stacktrace:
[1] ##core#449() at /home/mazzanti/.julia/packages/BenchmarkTools/7aqwe/src/execution.jl:297
[2] ##sample#450(::BenchmarkTools.Parameters) at /home/mazzanti/.julia/packages/BenchmarkTools/7aqwe/src/execution.jl:303
[3] #_run#16(::Bool, ::String, ::Base.Iterators.Pairs{Symbol,Integer,NTuple{4,Symbol},NamedTuple{(:samples, :evals, :gctrial, :gcsample),Tuple{Int64,Int64,Bool,Bool}}}, ::typeof(BenchmarkTools._run), ::BenchmarkTools.Benchmark{Symbol("##benchmark#448")}, ::BenchmarkTools.Parameters) at /home/mazzanti/.julia/packages/BenchmarkTools/7aqwe/src/execution.jl:331
[4] (::getfield(BenchmarkTools, Symbol("#kw##_run")))(::NamedTuple{(:verbose, :samples, :evals, :gctrial, :gcsample),Tuple{Bool,Int64,Int64,Bool,Bool}}, ::typeof(BenchmarkTools._run), ::BenchmarkTools.Benchmark{Symbol("##benchmark#448")}, ::BenchmarkTools.Parameters) at ./none:0
[5] (::getfield(Base, Symbol("#inner#2")){Base.Iterators.Pairs{Symbol,Integer,NTuple{5,Symbol},NamedTuple{(:verbose, :samples, :evals, :gctrial, :gcsample),Tuple{Bool,Int64,Int64,Bool,Bool}}},typeof(BenchmarkTools._run),Tuple{BenchmarkTools.Benchmark{Symbol("##benchmark#448")},BenchmarkTools.Parameters}})() at ./essentials.jl:793
[6] #invokelatest#1 at ./essentials.jl:794 [inlined]
[7] #invokelatest at ./none:0 [inlined]
[8] #run_result#37 at /home/mazzanti/.julia/packages/BenchmarkTools/7aqwe/src/execution.jl:32 [inlined]
[9] #run_result at ./none:0 [inlined]
[10] #run#39(::Base.Iterators.Pairs{Symbol,Integer,NTuple{5,Symbol},NamedTuple{(:verbose, :samples, :evals, :gctrial, :gcsample),Tuple{Bool,Int64,Int64,Bool,Bool}}}, ::typeof(run), ::BenchmarkTools.Benchmark{Symbol("##benchmark#448")}, ::BenchmarkTools.Parameters) at /home/mazzanti/.julia/packages/BenchmarkTools/7aqwe/src/execution.jl:46
[11] #run at ./none:0 [inlined] (repeats 2 times)
[12] #warmup#42 at /home/mazzanti/.julia/packages/BenchmarkTools/7aqwe/src/execution.jl:79 [inlined]
[13] warmup(::BenchmarkTools.Benchmark{Symbol("##benchmark#448")}) at /home/mazzanti/.julia/packages/BenchmarkTools/7aqwe/src/execution.jl:79
[14] top-level scope at /home/mazzanti/.julia/packages/BenchmarkTools/7aqwe/src/execution.jl:390
[15] top-level scope at In[93]:1
```
I can do
```julia
CuArray(rand([0.f0,1.f0],10))
```
but that takes more time than generating the numbers on the GPU 😕
Thanks a lot,
Ferran.
---
### Author:  [@jling](https://discourse.julialang.org/u/jling)
#### Post date: [November 10, 2019, 5:51pm UTC](https://discourse.julialang.org/t/random-numbers-in-0-f0-1-f0/30926/2 "2019-11-10T17:51:41Z")
you can try to do something like this:
> [@GPU randn way slower than rand?](https://discourse.julialang.org/t/gpu-randn-way-slower-than-rand/18236/3):
>
> Hi Tim, Thanks for the reply. I understand that testing once in global is not accurate, it’s just that the difference is too large to be normal. Here the new result following your code ac = Array{Float64}(undef, 2^20) ag = cu(ac) @btime randn!(ac) @btime CuArrays.@sync randn!(ag) 6.788 ms (0 allocations: 0 bytes) 7.626 s (5242883 allocations: 288.00 MiB) So the allocations are clearly the problem, but I can’t really figure out the reason. Even with rand there are some extra allocations @…
but as you noted bits are bytes anyways, so maybe you can just use a `if < 0.5` or something.
---
### Author:  [@maleadt](https://discourse.julialang.org/u/maleadt)
#### Post date: [November 10, 2019, 9:04pm UTC](https://discourse.julialang.org/t/random-numbers-in-0-f0-1-f0/30926/3 "2019-11-10T21:04:11Z")
Not all methods of `rand` are implemented for the GPU in CuArrays. If you have a need for a specific method, you can always file an issue (or better yet, have a look at how to implement it or extend the current functionality 🙂).