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mactavish96
ALP4-Tutorials
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c1b5d756
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c1b5d756
authored
2 years ago
by
Chao Zhan
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@@ -340,7 +340,7 @@ layout: center
...
@@ -340,7 +340,7 @@ layout: center
## MPI Collective Communication
## MPI Collective Communication
-
MPI collective operations involve all ranks in a given communicator at the same time.
-
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.
-
Some collective operations are globally synchronous.
---
---
...
@@ -478,3 +478,53 @@ MPI_Reduce (void *sendbuf, void *recvbuf, int count,
...
@@ -478,3 +478,53 @@ MPI_Reduce (void *sendbuf, void *recvbuf, int count,
-
**All predefined operations are associative and commutative**
-
**All predefined operations are associative and commutative**
-
**Beware of non-commutative effects on floats**
-
**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.
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