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slides/pages/recap.md

@@ -340,7 +340,7 @@ layout: center
 ## MPI Collective Communication
 
 - MPI collective operations involve all ranks in a given communicator at the same time.
-- All ranks must make the same MPI call for the operation to succeed.
+- **All ranks must make the same MPI call for the operation to succeed.**
 - Some collective operations are globally synchronous.
 
 ---
@@ -478,3 +478,53 @@ MPI_Reduce (void *sendbuf, void *recvbuf, int count,
     - **All predefined operations are associative and commutative**
     - **Beware of non-commutative effects on floats**
 
+---
+title: Global Reduction
+---
+
+## Global Reduction
+
+Some predefined operations for reduction:
+
+<div class="container flex justify-center mt-5">
+    <img src="/images/MPI-predefined-ops.png" class="block w-lg"/>
+</div>
+
+### Notes
+
+- You can create your own reduction operations (not covered here)
+
+---
+title: Global Reduction
+---
+
+## Global Reduction
+
+Perform an arithmetic reduction and broadcast the result:
+
+```c
+MPI_Allreduce (void *sendbuf, void *recvbuf, int count,
+    MPI_Datatype datatype, MPI_Op op, MPI_Comm comm)
+```
+
+### Notes
+
+- every rank receives the result of the reduction operation
+- equivalent to **MPI_Reduce + MPI_Bcast** with the same root
+- also beware of non-commutative effects
+
+---
+title: MPI Extensions
+---
+
+## MPI Extensions
+
+E.g. **MPI 2**, **MPI 3**, **MPI 4** ... (**MPI 5 is in the making**)
+
+Starting with MPI 2, the MPI standard has been extended with additional functionality:
+
+- Dynamic process management
+- File I/O
+- Shared memory
+
+See live demo.