Merge pull request #50 from SciML/as/inplace-getp

feat: add support for inplace getp

Author: ChrisRackauckas

src/parameter_indexing.jl

@@ -35,10 +35,15 @@ set_parameter!(sys, val, idx) = set_parameter!(parameter_values(sys), val, idx)
 """
     getp(sys, p)
 
-Return a function that takes an array representing the parameter vector or an integrator
+Return a function that takes an array representing the parameter object or an integrator
 or solution of `sys`, and returns the value of the parameter `p`. Note that `p` can be a
 direct index or a symbolic value, or an array/tuple of the aforementioned.
 
+If `p` is an array/tuple of parameters, then the returned function can also be used
+as an in-place getter function. The first argument is the buffer to which the parameter
+values should be written, and the second argument is the parameter object/integrator/
+solution from which the values are obtained.
+
 Requires that the integrator or solution implement [`parameter_values`](@ref). This function
 typically does not need to be implemented, and has a default implementation relying on
 [`parameter_values`](@ref).
@@ -57,8 +62,10 @@ end
 
 function _getp(sys, ::ScalarSymbolic, ::SymbolicTypeTrait, p)
     idx = parameter_index(sys, p)
-    return function getter(sol)
-        return parameter_values(sol, idx)
+    return let idx = idx
+        function getter(sol)
+            return parameter_values(sol, idx)
+        end
     end
 end
 
@@ -70,8 +77,16 @@ for (t1, t2) in [
     @eval function _getp(sys, ::NotSymbolic, ::$t1, p::$t2)
         getters = getp.((sys,), p)
 
-        return function getter(sol)
-            map(g -> g(sol), getters)
+        return let getters = getters
+            function getter(sol)
+                map(g -> g(sol), getters)
+            end
+            function getter(buffer, sol)
+                for (i, g) in zip(eachindex(buffer), getters)
+                    buffer[i] = g(sol)
+                end
+                buffer
+            end
         end
     end
 end

test/parameter_indexing_test.jl

@@ -56,3 +56,15 @@ for (sym, oldval, newval, check_inference) in [
     set!(p, oldval)
     @test get(p) == oldval
 end
+
+for (sym, val) in [
+    ([:a, :b, :c], p),
+    ([:c, :a], p[[3, 1]]),
+    ((:b, :a), p[[2, 1]]),
+    ((1, :c), p[[1, 3]])
+]
+    buffer = zeros(length(sym))
+    get = getp(sys, sym)
+    @inferred get(buffer, fi)
+    @test buffer == val
+end