Enable Reactant AD through parallel spin kernels

KomaMRICore/src/datatypes/Spinor.jl

@@ -155,7 +155,13 @@ Spinor rotation matrix. Counter-clockwise rotation of `φ` with respect to the a
   (NMR imaging). IEEE Transactions on Medical Imaging, 10(1), 53-65.
   doi:10.1109/42.75611
 """
-Q(φ, nxy, nz) = Spinor(cos.(φ/2).-1im*nz.*sin.(φ/2), -1im*nxy.*sin.(φ/2))
+function Q(φ, nxy, nz)
+    neg_im = complex(zero(eltype(φ)), -one(eltype(φ)))
+    return Spinor(
+        (@. cos(φ / 2) + neg_im * nz * sin(φ / 2)),
+        (@. neg_im * nxy * sin(φ / 2)),
+    )
+end
 
 """
     y = abs(s::Spinor)

KomaMRICore/src/simulation/SimMethods/BlochSimple/BlochSimple.jl

@@ -76,11 +76,13 @@ function run_spin_precession!(
     outflow_spin_reset!(Mxy, seq.t[2:end]', p.motion)
     outflow_spin_reset!(M, seq.t[2:end]', p.motion; replace_by=p.ρ)
     #Acquired signal
-    adc = findall(cpu(seq.ADC[2:end]))
-    Mxy_adc = Mxy[:, adc]
-    acquire_block_signal!(
-        sig, Mxy_adc, sys.receiver, p.motion, (x, y, z), adc,
-    )
+    if !isempty(sig)
+        adc = findall(cpu(seq.ADC[2:end]))
+        Mxy_adc = Mxy[:, adc]
+        acquire_block_signal!(
+            sig, Mxy_adc, sys.receiver, p.motion, (x, y, z), adc,
+        )
+    end
     return nothing
 end
 

KomaMRICore/src/simulation/SimulatorCore.jl

@@ -108,12 +108,21 @@ function run_spin_precession_parallel!(
     prealloc::PreallocResult;
     Nthreads=Threads.nthreads(),
 )
-    parts = kfoldperm(length(obj), Nthreads)
-
-    ThreadsX.foreach(enumerate(parts)) do (i, p)
+    if Nthreads == 1
+        p = 1:length(obj)
         run_spin_precession!(
-            @view(obj[p]), seq, split_sig_per_thread(sig, i, p, sim_method), @view(Xt[p]), sys, sim_method, groupsize, backend, @view(prealloc[p])
+            obj, seq, split_sig_per_thread(sig, 1, p, sim_method), Xt, sys,
+            sim_method, groupsize, backend, prealloc
         )
+    else
+        parts = kfoldperm(length(obj), Nthreads)
+
+        ThreadsX.foreach(enumerate(parts)) do (i, p)
+            run_spin_precession!(
+                @view(obj[p]), seq, split_sig_per_thread(sig, i, p, sim_method),
+                @view(Xt[p]), sys, sim_method, groupsize, backend, @view(prealloc[p])
+            )
+        end
     end
 
     return nothing
@@ -131,13 +140,21 @@ function run_spin_excitation_parallel!(
     prealloc::PreallocResult;
     Nthreads=Threads.nthreads(),
 )
-    parts = kfoldperm(length(obj), Nthreads)
-
-    ThreadsX.foreach(enumerate(parts)) do (i, p)
+    if Nthreads == 1
+        p = 1:length(obj)
         run_spin_excitation!(
-            @view(obj[p]), seq, split_sig_per_thread(sig, i, p, sim_method), @view(Xt[p]),
-            sys, sim_method, groupsize, backend, @view(prealloc[p])
+            obj, seq, split_sig_per_thread(sig, 1, p, sim_method), Xt,
+            sys, sim_method, groupsize, backend, prealloc
         )
+    else
+        parts = kfoldperm(length(obj), Nthreads)
+
+        ThreadsX.foreach(enumerate(parts)) do (i, p)
+            run_spin_excitation!(
+                @view(obj[p]), seq, split_sig_per_thread(sig, i, p, sim_method), @view(Xt[p]),
+                sys, sim_method, groupsize, backend, @view(prealloc[p])
+            )
+        end
     end
 
     return nothing