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Refactor _readSelection. #315

Merged
merged 1 commit into from
Nov 29, 2023
Merged

Refactor _readSelection. #315

merged 1 commit into from
Nov 29, 2023

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1uc
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@1uc 1uc commented Nov 14, 2023

This commit refactors _readSelection in such a manner that:

  1. Canonical selections don't require post-read shuffling.
  2. The reading of the dataset is moved to a separate function.

As a consequence, there's no need for an optimization for std::string, since
those only matters when reading from the "@library", which should only happen
indirectly. Hence, we free to ensure that those are always canonical.

@1uc 1uc force-pushed the 1uc/refactor-_readSelection branch from 38f7684 to 8294b8e Compare November 14, 2023 10:17
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1uc commented Nov 14, 2023

This is a preparatory PR for #307

@1uc 1uc marked this pull request as ready for review November 14, 2023 10:52
@1uc 1uc force-pushed the 1uc/refactor-_readSelection branch from 8294b8e to 7558311 Compare November 22, 2023 14:48
@1uc 1uc force-pushed the 1uc/refactor-_readSelection branch 2 times, most recently from 8f7f0ee to f8b56c9 Compare November 27, 2023 16:02
This commit refactors `_readSelection` in such a manner that:
  1. Canonical selections don't require post-read shuffling.
  2. The reading of the dataset is moved to a separate function.

As a consequence, there's no need for an optimization for `std::string`, since
those only mattern when reading from the `"@library"`, which should only happen
indirectly. Hence, we free to ensure that those are always canonical.
@1uc 1uc force-pushed the 1uc/refactor-_readSelection branch from f8b56c9 to a6915c6 Compare November 27, 2023 16:03
@matz-e matz-e requested a review from mgeplf November 27, 2023 16:44
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LGTM

@1uc 1uc merged commit c2e8b5e into master Nov 29, 2023
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@1uc 1uc deleted the 1uc/refactor-_readSelection branch November 29, 2023 07:04
1uc added a commit that referenced this pull request Nov 30, 2023
This commit refactors `_readSelection` in such a manner that:
  1. Canonical selections don't require post-read shuffling.
  2. The reading of the dataset is moved to a separate function.

As a consequence, there's no need for an optimization for `std::string`, since
those only mattern when reading from the `"@library"`, which should only happen
indirectly. Hence, we free to ensure that those are always canonical.
WeinaJi pushed a commit to BlueBrain/neurodamus that referenced this pull request Jan 29, 2024
## Context
When using `WholeCell` load-balancing, the access pattern when reading
parameters during synapse creation is extremely poor and is the main
reason why we see long (10+ minutes) periods of severe performance
degradation of our parallel filesystem when running slightly larger
simulations on BB5.

Using Darshan and several PoCs we established that the time required to
read these parameters can be reduced by more than 8x and IOps can be
reduced by over 1000x when using collective MPI-IO. Moreover, the
"waiters" where reduced substantially as well. See BBPBGLIB-1070.

Following those finding we concluded that neurodamus would need to use
collective MPI-IO in the future.

We've implemented most of the required changes directly in libsonata
allowing others to benefit from the same optimizations should the need
arise. See,
BlueBrain/libsonata#309
BlueBrain/libsonata#307

and preparatory work:
BlueBrain/libsonata#315
BlueBrain/libsonata#314
BlueBrain/libsonata#298 

By instrumenting two simulations (SSCX and reduced MMB) we concluded
that neurodamus was almost collective. However, certain attributes where
read in different order on different MPI ranks. Maybe due to salting
hashes differently on different MPI ranks.

## Scope
This PR enables neurodamus to use collective IO for the simulation
described above.

## Testing
<!--
Please add a new test under `tests`. Consider the following cases:

1. If the change is in an independent component (e.g, a new container
type, a parser, etc) a bare unit test should be sufficient. See e.g.
`tests/test_coords.py`
2. If you are fixing or adding components supporting a scientific use
case, affecting node or synapse creation, etc..., which typically rely
on Neuron, tests should set up a simulation using that feature,
instantiate neurodamus, **assess the state**, run the simulation and
check the results are as expected.
    See an example at `tests/test_simulation.py#L66`
-->
We successfully ran the reduced MMB simulation, but since SSCX hasn't
been converted to SONATA, we can't run that simulation.

## Review
* [x] PR description is complete
* [x] Coding style (imports, function length, New functions, classes or
files) are good
* [ ] Unit/Scientific test added
* [ ] Updated Readme, in-code, developer documentation

---------

Co-authored-by: Luc Grosheintz <luc.grosheintz@gmail.ch>
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3 participants