Add Poplar.get_ipu_model to more easily obtain an IPU Model

docs/src/poplar.md

@@ -49,6 +49,21 @@ You can slice a tensor with the usual Julia notation `tensor[index1:index2]`, th
 
 [`similar`](@ref) can be used to add to `graph` a tensor with the same shape and optionally element type as `tensor`, while [`copyto!`](@ref) can be used to copy elements of a CPU host array into an IPU tensor.
 
+## Using `IPUToolkit.jl` without an IPU
+
+While this package requires a physical IPU to use all the available features, you can still experiment with the IPU programming model even if you do not have access to a hardware IPU.
+The Poplar SDK provides a feature called IPU Model, which is a software emulation of the behaviour of the IPU hardware.
+While the IPU model comes with [some limitations](https://docs.graphcore.ai/projects/poplar-user-guide/en/latest/poplar_programs.html#programming-with-poplar), it can be useful for testing or debugging.
+
+To use the IPU model in `IPUToolkit.jl`, define the device of your IPU program with `Poplar.IPUModelCreateDevice` (which calls [`IPUModel::createDevice`](https://docs.graphcore.ai/projects/poplar-api/en/3.4.0/poplar/profiling/IPUModel.html#_CPPv4NK6poplar8IPUModel12createDeviceE11OptionFlagsbj) under the hood):
+```julia
+device = Poplar.get_ipu_model()
+# Then the rest of the program continues as usual
+target = Poplar.DeviceGetTarget(device)
+graph = Poplar.Graph(target)
+# ...
+```
+
 ```@autodocs
 Modules = [IPUToolkit.Poplar]
 ```

src/poplar.jl

@@ -207,7 +207,7 @@ const ATTACHED_DEVICES_LOCK = ReentrantLock()
 
 # Be sure to quit all julia sessions which hold devices!!!
 """
-    Poplar.get_ipu_devices(n::Int, hint::Union{AbstractVector{<:Integer},Integer}=0)
+    Poplar.get_ipu_devices(n::Int, hint::Union{AbstractVector{<:Integer},Integer}=0) -> Vector{Poplar.DeviceAllocated}
 
 Try to attach to `n` IPU devices, returns a vector of the pointers to the devices
 successfully attached to.  You can release them with `Poplar.DeviceDetach` (note that this
@@ -222,8 +222,8 @@ attach.  It can have different types:
 * if of type `AbstractVector`, try to attach to `n` devices from that list of
   IDs.
 
-See [`Poplar.get_ipu_device`](@ref) for requesting exactly one IPU device.
-To release all devices previously attached with `Poplar.get_ipu_devices` or [`Poplar.get_ipu_device`](@ref) use [`Poplar.detach_devices`](@ref).
+See [`Poplar.get_ipu_device`](@ref) for requesting exactly one IPU device, and [`Poplar.get_ipu_model`](@ref) for requesting an IPU Model.
+To release all devices previously attached with `Poplar.get_ipu_devices`, [`Poplar.get_ipu_device`](@ref), or [`Poplar.get_ipu_model`](@ref) use [`Poplar.detach_devices`](@ref).
 """
 function get_ipu_devices(n::Int, hint::Union{AbstractVector{<:Integer},Integer}=0)
     lock(ATTACHED_DEVICES_LOCK) do
@@ -261,12 +261,16 @@ function get_ipu_devices(n::Int, hint::Union{AbstractVector{<:Integer},Integer}=
 end
 
 """
-    Poplar.get_ipu_device(hint::Union{AbstractVector{<:Integer},Integer}=0)
+    Poplar.get_ipu_device(hint::Union{AbstractVector{<:Integer},Integer}=0) -> Poplar.DeviceAllocated
 
 Similar to [`Poplar.get_ipu_devices`](@ref), but request exactly one IPU device.  If it can attach
 to a device, return that pointer only (not in a vector, like `get_ipu_devices`), otherwise
-return `nothing`.  You can release the device with `Poplar.DeviceDetach(device)`.
-To release all devices previously attached with `Poplar.get_ipu_device` or [`Poplar.get_ipu_devices`](@ref) use [`Poplar.detach_devices`](@ref).
+return `nothing`.
+
+See [`Poplar.get_ipu_model`](@ref) for requesting an IPU Model.
+
+You can release the device with `Poplar.DeviceDetach(device)`.
+To release all devices previously attached with `Poplar.get_ipu_device`, [`Poplar.get_ipu_devices`](@ref), or [`Poplar.get_ipu_model`](@ref) use [`Poplar.detach_devices`](@ref).
 
 The optional argument `hint` suggests to which device IDs to try and
 attach.  It can have different types:
@@ -283,6 +287,29 @@ function get_ipu_device(hint::Union{AbstractVector{<:Integer},Integer}=0)
     return nothing
 end
 
+"""
+    Poplar.get_ipu_model(ipu_version::String="ipu2") -> Poplar.DeviceAllocated
+
+Attach to an [IPU Model](https://docs.graphcore.ai/projects/poplar-user-guide/en/latest/poplar_programs.html#programming-with-poplar), and return the attached device.
+This uses [`IPUModel::createDevice`](https://docs.graphcore.ai/projects/poplar-api/en/3.4.0/poplar/profiling/IPUModel.html#_CPPv4NK6poplar8IPUModel12createDeviceE11OptionFlagsbj) under the hood.
+
+The optional positional argument `ipu_version::String`, `ipu2` by default`, represents the version of the IPU to emulate.
+Valid values for `ipu_version` are `ipu1` and `ipu2` (for Mk1 and Mk2 IPU architectures respectively).
+
+See [`Poplar.get_ipu_device`](@ref) and [`Poplar.get_ipu_devices`](@ref) for requesting one or mode hardware IPUs.
+
+You can release the device with `Poplar.DeviceDetach(device)`.
+To release all devices previously attached with `Poplar.get_ipu_model`, [`Poplar.get_ipu_device`](@ref) or [`Poplar.get_ipu_devices`](@ref) use [`Poplar.detach_devices`](@ref).
+"""
+function get_ipu_model(ipu_version::String="ipu2")
+    lock(ATTACHED_DEVICES_LOCK) do
+        model = Poplar.IPUModel(ipu_version)
+        device = Poplar.IPUModelCreateDevice(model)
+        append!(ATTACHED_DEVICES, attached_devices)
+        device
+    end
+end
+
 """
     Poplar.detach_devices() -> Nothing
 

test/compiler.jl

@@ -347,8 +347,7 @@ end
                                match_mode=:any,
                                Poplar.get_ipu_device())
                 else
-                    model = @cxxtest Poplar.IPUModel()
-                    Poplar.IPUModelCreateDevice(model)
+                    Poplar.get_ipu_model()
                 end
 
                 # Run a test program

test/poplar.jl

@@ -100,8 +100,7 @@ end
 
     # Test a simple program using a software-emulated IPU (IPU model)
     @testset "IPU Model" begin
-        model = @cxxtest Poplar.IPUModel()
-        device = @cxxtest Poplar.IPUModelCreateDevice(model)
+        device = @cxxtest Poplar.get_ipu_model()
         test_poplar_program(device)
     end