Update README.md

Author: SimonDanisch

README.md

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 # CLArrays
+
+Implementation of the [abstract GPU Array Interface](https://github.com/JuliaGPU/GPUArrays.jl)
+
+CLArray uses [Transpiler.jl](https://github.com/SimonDanisch/Transpiler.jl) to compile Julia functions for the GPU using OpenCL.
+
+It implements the full abstract gpu interface in GPUArrays.
+To learn how to use it, please refer to the GPUArray documentations:
+
+[![](https://img.shields.io/badge/docs-latest-blue.svg)](https://JuliaGPU.github.io/GPUArrays.jl/latest)
+
+The only noteworthy interface that isn't mentioned in GPUArrays is how to select and initialize devices:
+
+```Julia
+using CLArrays
+
+for dev in CLArrays.devices()
+    CLArrays.init(dev)
+    x = zeros(CLArray{Float32}, 5, 5) # create a CLArray on device `dev`
+end
+# you can also filter with is_gpu, is_cpu
+gpu_devices = CLArrays.devices(is_gpu)
+```