Add to pre

include/genn/genn/code_generator/groupMerged.h

@@ -613,6 +613,9 @@ class GENN_EXPORT NeuronGroupMergedBase : public GroupMerged<NeuronGroupInternal
     //! Get sorted vectors of merged incoming synapse groups belonging to archetype group
     const std::vector<SynapseGroupInternal*> &getSortedArchetypeMergedInSyns() const { return m_SortedMergedInSyns.front(); }
 
+    //! Get sorted vectors of merged outgoing synapse groups with presynaptic output belonging to archetype group
+    const std::vector<SynapseGroupInternal*> &getSortedArchetypeMergedPreOutputOutSyns() const { return m_SortedMergedPreOutputOutSyns.front(); }
+
     //! Get sorted vectors of current sources belonging to archetype group
     const std::vector<CurrentSourceInternal*> &getSortedArchetypeCurrentSources() const { return m_SortedCurrentSources.front(); }
 
@@ -914,12 +917,16 @@ class GENN_EXPORT NeuronGroupMergedBase : public GroupMerged<NeuronGroupInternal
     void addMergedInSynPointerField(const std::string &type, const std::string &name,
                                     size_t archetypeIndex, const std::string &prefix);
 
+    void addMergedPreOutputOutSynPointerField(const std::string &type, const std::string &name,
+                                    size_t archetypeIndex, const std::string &prefix);
+
 
 private:
     //------------------------------------------------------------------------
     // Members
     //------------------------------------------------------------------------
     std::vector<std::vector<SynapseGroupInternal*>> m_SortedMergedInSyns;
+    std::vector<std::vector<SynapseGroupInternal*>> m_SortedMergedPreOutputOutSyns;
     std::vector<std::vector<CurrentSourceInternal*>> m_SortedCurrentSources;
 };
 
@@ -1077,6 +1084,11 @@ class GENN_EXPORT SynapseGroupMergedBase : public GroupMerged<SynapseGroupIntern
         return ((batchSize == 1) ? "" : "postBatchOffset + ") + index;
     }
 
+    static std::string getPreISynIndex(unsigned int batchSize, const std::string &index)
+    {
+        return ((batchSize == 1) ? "" : "preBatchOffset + ") + index;
+    }
+
     static std::string getSynVarIndex(unsigned int batchSize, VarAccessDuplication varDuplication, const std::string &index);
 
 protected:
@@ -1108,6 +1120,7 @@ class GENN_EXPORT SynapseGroupMergedBase : public GroupMerged<SynapseGroupIntern
     // Private methods
     //------------------------------------------------------------------------
     void addPSPointerField(const std::string &type, const std::string &name, const std::string &prefix);
+    void addPreOutputPointerField(const std::string &type, const std::string &name, const std::string &prefix);
     void addSrcPointerField(const std::string &type, const std::string &name, const std::string &prefix);
     void addTrgPointerField(const std::string &type, const std::string &name, const std::string &prefix);
     void addWeightSharingPointerField(const std::string &type, const std::string &name, const std::string &prefix);

include/genn/genn/neuronGroup.h

@@ -237,6 +237,7 @@ class GENN_EXPORT NeuronGroup
     const std::vector<SynapseGroupInternal*> &getOutSyn() const{ return m_OutSyn; }
     const std::vector<SynapseGroupInternal *> &getFusedWUPreOutSyn() const { return m_FusedWUPreOutSyn; }
 
+     const std::vector<SynapseGroupInternal *> &getFusedPreOuptputOutSyn() const { return m_FusedPreOutputOutSyn; }   
 
     //! Gets pointers to all current sources which provide input to this neuron group
     const std::vector<CurrentSourceInternal*> &getCurrentSources() const { return m_CurrentSources; }
@@ -297,6 +298,7 @@ class GENN_EXPORT NeuronGroup
     std::vector<SynapseGroupInternal*> m_FusedPSMInSyn;
     std::vector<SynapseGroupInternal *> m_FusedWUPostInSyn;
     std::vector<SynapseGroupInternal *> m_FusedWUPreOutSyn;
+    std::vector<SynapseGroupInternal *> m_FusedPreOutputOutSyn;
     std::set<SpikeEventThreshold> m_SpikeEventCondition;
     unsigned int m_NumDelaySlots;
     std::vector<CurrentSourceInternal*> m_CurrentSources;

include/genn/genn/neuronGroupInternal.h

@@ -28,6 +28,7 @@ class NeuronGroupInternal : public NeuronGroup
     using NeuronGroup::injectCurrent;
     using NeuronGroup::getFusedPSMInSyn;
     using NeuronGroup::getFusedWUPostInSyn;
+    using NeuronGroup::getFusedPreOuptputOutSyn;
     using NeuronGroup::getFusedWUPreOutSyn;
     using NeuronGroup::getOutSyn;
     using NeuronGroup::getCurrentSources;

include/genn/genn/synapseGroup.h

@@ -68,6 +68,10 @@ class GENN_EXPORT SynapseGroup
     /*! This should either be 'Isyn' or the name of one of the postsynaptic neuron's additional input variables. */
     void setPSTargetVar(const std::string &varName);
 
+    //! Set name of neuron input variable $(addToPre, . ) commands will target
+    /*! This should either be 'Isyn' or the name of one of the presynaptic neuron's additional input variables. */
+    void setPreTargetVar(const std::string &varName);
+
     //! Set location of sparse connectivity initialiser extra global parameter
     /*! This is ignored for simulations on hardware with a single memory space
         and only applies to extra global parameters which are pointers. */
@@ -221,6 +225,10 @@ class GENN_EXPORT SynapseGroup
     //! Get name of neuron input variable postsynaptic model will target
     /*! This will either be 'Isyn' or the name of one of the postsynaptic neuron's additional input variables. */
     const std::string &getPSTargetVar() const{ return m_PSTargetVar; }
+
+    //! Get name of neuron input variable which a presynaptic output specified with $(addToPre) will target
+    /*! This will either be 'Isyn' or the name of one of the presynaptic neuron's additional input variables. */
+    const std::string &getPreTargetVar() const{ return m_PreTargetVar; }
 
     //! Get location of sparse connectivity initialiser extra global parameter by name
     /*! This is only used by extra global parameters which are pointers*/
@@ -233,6 +241,9 @@ class GENN_EXPORT SynapseGroup
     //! Does this synapse group require dendritic delay?
     bool isDendriticDelayRequired() const;
 
+    //! Does this synapse group define presynaptic output?
+    bool isPresynapticOutputRequired() const;    
+
     //! Does this synapse group require an RNG to generate procedural connectivity?
     bool isProceduralConnectivityRNGRequired() const;
 
@@ -280,6 +291,7 @@ class GENN_EXPORT SynapseGroup
     void setFusedPSVarSuffix(const std::string &suffix){ m_FusedPSVarSuffix = suffix; }
     void setFusedWUPreVarSuffix(const std::string &suffix){ m_FusedWUPreVarSuffix = suffix; }
     void setFusedWUPostVarSuffix(const std::string &suffix){ m_FusedWUPostVarSuffix = suffix; }
+    void setFusedPreOutputSuffix(const std::string &suffix){ m_FusedPreOutputSuffix = suffix; }
 
     void initDerivedParams(double dt);
 
@@ -301,6 +313,7 @@ class GENN_EXPORT SynapseGroup
     const std::string &getFusedPSVarSuffix() const{ return m_FusedPSVarSuffix; }
     const std::string &getFusedWUPreVarSuffix() const { return m_FusedWUPreVarSuffix; }
     const std::string &getFusedWUPostVarSuffix() const { return m_FusedWUPostVarSuffix; }
+    const std::string &getFusedPreOutputSuffix() const { return m_FusedPreOutputSuffix; }
 
     //! Are any of this synapse group's weight update model variables referenced by a custom update
     bool areWUVarReferencedByCustomUpdate() const { return m_WUVarReferencedByCustomUpdate;  }
@@ -310,6 +323,9 @@ class GENN_EXPORT SynapseGroup
 
     //! Can presynaptic update component of this synapse group's weight update model be safely fused with other whose hashes match so only one needs simulating at all?
     bool canWUMPreUpdateBeFused() const;
+
+     //! Can presynaptic output component of this synapse group's weight update model be safely fused with other whose hashes match so only one needs simulating at all?
+    bool canPreOutputBeFused() const;   
 
     //! Can postsynaptic update component of this synapse group's weight update model be safely fused with other whose hashes match so only one needs simulating at all?
     bool canWUMPostUpdateBeFused() const;
@@ -345,6 +361,10 @@ class GENN_EXPORT SynapseGroup
     /*! NOTE: this can only be called after model is finalized */
     boost::uuids::detail::sha1::digest_type getPSFuseHashDigest() const;
 
+    //! Generate hash of presynaptic output update component of this synapse group 
+     /*! NOTE: this can only be called after model is finalized */
+    boost::uuids::detail::sha1::digest_type getPreOutputHashDigest() const;
+
     boost::uuids::detail::sha1::digest_type getDendriticDelayUpdateHashDigest() const;
 
     //! Generate hash of initialisation component of this synapse group
@@ -500,7 +520,15 @@ class GENN_EXPORT SynapseGroup
     /*! This may not be the name of this synapse group if it has been fused */
     std::string m_FusedWUPostVarSuffix;
 
+    //! Suffix for weight update model presynaptic output variable
+    /*! This may not be the name of this synapse group if it has been fused */
+    std::string m_FusedPreOutputSuffix;
+
     //! Name of neuron input variable postsynaptic model will target
     /*! This should either be 'Isyn' or the name of one of the postsynaptic neuron's additional input variables. */
     std::string m_PSTargetVar;
+
+    //! Name of neuron input variable a presynaptic output specified with $(addToPre) will target
+    /*! This will either be 'Isyn' or the name of one of the presynaptic neuron's additional input variables. */
+    std::string m_PreTargetVar;
 };

include/genn/genn/synapseGroupInternal.h

@@ -34,23 +34,27 @@ class SynapseGroupInternal : public SynapseGroup
     using SynapseGroup::setEventThresholdReTestRequired;
     using SynapseGroup::setWUVarReferencedByCustomUpdate;
     using SynapseGroup::setFusedPSVarSuffix;
+    using SynapseGroup::setFusedPreOutputSuffix;
     using SynapseGroup::setFusedWUPreVarSuffix;
     using SynapseGroup::setFusedWUPostVarSuffix;
     using SynapseGroup::initDerivedParams;
     using SynapseGroup::isEventThresholdReTestRequired;
     using SynapseGroup::areWUVarReferencedByCustomUpdate;
     using SynapseGroup::getFusedPSVarSuffix;
+    using SynapseGroup::getFusedPreOutputSuffix;
     using SynapseGroup::getFusedWUPreVarSuffix;
     using SynapseGroup::getFusedWUPostVarSuffix;
     using SynapseGroup::getSparseIndType;
     using SynapseGroup::canPSBeFused;
     using SynapseGroup::canWUMPreUpdateBeFused;
     using SynapseGroup::canWUMPostUpdateBeFused;
+    using SynapseGroup::canPreOutputBeFused;
     using SynapseGroup::getWUHashDigest;
     using SynapseGroup::getWUPreHashDigest;
     using SynapseGroup::getWUPostHashDigest;
     using SynapseGroup::getPSHashDigest;
     using SynapseGroup::getPSFuseHashDigest;
+    using SynapseGroup::getPreOutputHashDigest;
     using SynapseGroup::getWUPreFuseHashDigest;
     using SynapseGroup::getWUPostFuseHashDigest;
     using SynapseGroup::getDendriticDelayUpdateHashDigest;

src/genn/backends/single_threaded_cpu/backend.cc

@@ -342,6 +342,9 @@ void Backend::genSynapseUpdate(CodeStream &os, const ModelSpecMerged &modelMerge
                                 synSubs.addFuncSubstitution("addToInSyn", 1, "group->inSyn[" + s.getPostISynIndex(1, "j") + "] += $(0)");
                             }
 
+			    if(s.getArchetype().isPresynapticOutputRequired()) {
+			        synSubs.addFuncSubstitution("addToPre", 1, "group->revInSyn[" + s.getPreISynIndex(1, synSubs["id_pre"]) + "] += $(0)");
+                            }
                             // Call synapse dynamics handler
                             s.generateSynapseUpdate(*this, os, modelMerged, synSubs);
                         }
@@ -364,7 +367,7 @@ void Backend::genSynapseUpdate(CodeStream &os, const ModelSpecMerged &modelMerge
                     os << "const auto *group = &mergedPresynapticUpdateGroup" << s.getIndex() << "[g]; " << std::endl;
 
                     genSynapseIndexCalculation(os, s, 1);
-
+                    
                     // generate the code for processing spike-like events
                     if (s.getArchetype().isSpikeEventRequired()) {
                         genPresynapticUpdate(os, modelMerged, s, funcSubs, false);
@@ -435,7 +438,10 @@ void Backend::genSynapseUpdate(CodeStream &os, const ModelSpecMerged &modelMerge
                                 synSubs.addVarSubstitution("id_syn", "((group->numTrgNeurons * i) + spike)");
                             }
                             synSubs.addVarSubstitution("id_post", "spike");
-
+			    if (s.getArchetype().isPresynapticOutputRequired()) {
+			        synSubs.addFuncSubstitution("addToPre", 1, "group->revInSyn[" + s.getPreISynIndex(1, synSubs["id_pre"]) + "] += $(0)");        
+                            }
+
                             s.generateSynapseUpdate(*this, os, modelMerged, synSubs);
                         }
                     }
@@ -1453,6 +1459,10 @@ void Backend::genPresynapticUpdate(CodeStream &os, const ModelSpecMerged &modelM
             synSubs.addFuncSubstitution("addToInSyn", 1, "group->inSyn[" + sg.getPostISynIndex(1, "ipost") + "] += $(0)");
         }
 
+	if (sg.getArchetype().isPresynapticOutputRequired()) {
+	    synSubs.addFuncSubstitution("addToPre", 1, "group->revInSyn[" + sg.getPreISynIndex(1, synSubs["id_pre"]) + "] += $(0)");
+	}
+
         if (sg.getArchetype().getMatrixType() & SynapseMatrixConnectivity::SPARSE) {
             os << "const unsigned int npost = group->rowLength[ipre];" << std::endl;
             os << "for (unsigned int j = 0; j < npost; j++)";

src/genn/genn/code_generator/backendSIMT.cc

@@ -247,7 +247,7 @@ void BackendSIMT::genNeuronPrevSpikeTimeUpdateKernel(CodeStream &os, const Subst
     genParallelGroup<NeuronPrevSpikeTimeUpdateGroupMerged>(
         os, kernelSubs, modelMerged.getMergedNeuronPrevSpikeTimeUpdateGroups(), idStart,
         [this](const NeuronGroupInternal &ng) { return padKernelSize(ng.getNumNeurons(), KernelNeuronUpdate); },
-        [batchSize, this](CodeStream &os, const NeuronPrevSpikeTimeUpdateGroupMerged &ng, Substitutions &popSubs)
+        [batchSize,this](CodeStream &os, const NeuronPrevSpikeTimeUpdateGroupMerged &ng, Substitutions &popSubs)
         {
             CodeStream::Scope b(os);
 
@@ -737,6 +737,11 @@ void BackendSIMT::genPostsynapticUpdateKernel(CodeStream &os, const Substitution
                         synSubs.addVarSubstitution("id_post", "shSpk[j]");
                         synSubs.addVarSubstitution("id_syn", "synAddress");
 
+                        if(sg.getArchetype().isPresynapticOutputRequired()) {
+                            synSubs.addFuncSubstitution("addToPre", 1,
+                                                        getAtomic(modelMerged.getModel().getPrecision()) + "(&group->revInSyn[" + sg.getPreISynIndex(batchSize, synSubs["id_pre"]) + "], $(0))");
+                        }
+
                         sg.generateSynapseUpdate(*this, os, modelMerged, synSubs);
 
                         if (sg.getArchetype().getMatrixType() & SynapseMatrixConnectivity::SPARSE) {
@@ -797,7 +802,12 @@ void BackendSIMT::genSynapseDynamicsKernel(CodeStream &os, const Substitutions &
                 else {
                     synSubs.addFuncSubstitution("addToInSyn", 1, getAtomic(modelMerged.getModel().getPrecision()) + "(&group->inSyn[" + sg.getPostISynIndex(batchSize, synSubs["id_post"]) + "], $(0))");
                 }
-
+
+                if(sg.getArchetype().isPresynapticOutputRequired()) {
+                    synSubs.addFuncSubstitution("addToPre", 1,
+                                                getAtomic(modelMerged.getModel().getPrecision()) + "(&group->revInSyn[" + sg.getPreISynIndex(batchSize, synSubs["id_pre"]) + "], $(0))");
+                }
+
                 sg.generateSynapseUpdate(*this, os, modelMerged, synSubs);
             }
         });

src/genn/genn/code_generator/generateRunner.cc

@@ -1152,6 +1152,12 @@ MemAlloc CodeGenerator::generateRunner(const filesystem::path &outputPath, const
                 }
             }
         }
+        // Loop through fused outgoing synapse populations with weightupdate models that have presynaptic output 
+        for(const auto *sg : n.second.getFusedPreOuptputOutSyn()) {
+            backend.genArray(definitionsVar, definitionsInternalVar, runnerVarDecl, runnerVarAlloc, runnerVarFree,
+                             model.getPrecision(), "revInSyn" + sg->getFusedPreOutputSuffix(), sg->getInSynLocation(),
+                             sg->getSrcNeuronGroup()->getNumNeurons() * batchSize, mem);
+        }
 
         // Loop through merged postsynaptic weight updates of incoming synaptic populations
         for(const auto *sg: n.second.getFusedWUPreOutSyn()) {