Feat: channel excess buffer

[lterrac]

Description

Variable size SPSC channel:

• the payload is not split into chunks. We require the user to provide a bigger buffer (ideally double the capacity of the channel), and we use part of it to store entire tokens. The channel logic remains unchanged and it allows you to push only MAX_TOKENS * TOKEN_SIZE
• channels take into account both how many tokens are in the channel and the available space
• extended the isFull function to take a size_t and compute whether a push with such size can be made.
• add MPI tests for channel testing the following:
  - a single push that fills the payload buffer
  - a series of push that fills the payload buffer
  - a series of push that fills the coordination buffer
  - push-pop-push with a buffer big enough to force the second push to use the excess buffer

Type of change

• CHANGE (fix or feature that would cause existing functionality to not work as expected)
• FEATURE (non-breaking change which adds functionality)
• BUGFIX (non-breaking change which fixes an issue)
• ENHANCEMENT (non-breaking change which improves existing functionality)
• NONE (if none of the other choices apply. Example, tooling, build system, CI, docs, etc.)

Verification

Added mpi test for variable size spsc channel

[github-actions]

Coverage arm64

Package	Line Rate	Branch Rate	Health
include.hicr.backends.boost	75%	43%	➖
include.hicr.backends.hwloc	77%	37%	➖
include.hicr.backends.mpi	92%	52%	✔
include.hicr.backends.nosv	71%	45%	➖
include.hicr.backends.pthreads	89%	49%	✔
include.hicr.core	73%	45%	➖
include.hicr.frontends.RPCEngine	100%	48%	✔
include.hicr.frontends.channel	95%	62%	✔
include.hicr.frontends.channel.fixedSize	100%	50%	✔
include.hicr.frontends.channel.fixedSize.mpsc.locking	92%	62%	✔
include.hicr.frontends.channel.fixedSize.mpsc.nonlocking	94%	55%	✔
include.hicr.frontends.channel.fixedSize.spsc	95%	68%	✔
include.hicr.frontends.channel.variableSize	95%	50%	✔
include.hicr.frontends.channel.variableSize.mpsc.locking	84%	52%	✔
include.hicr.frontends.channel.variableSize.mpsc.nonlocking	95%	48%	✔
include.hicr.frontends.channel.variableSize.spsc	92%	60%	✔
include.hicr.frontends.objectStore	63%	41%	➖
include.hicr.frontends.tasking	80%	56%	✔
Summary	83% (1952 / 2340)	48% (1133 / 2371)	✔

Minimum allowed line rate is 60%

[github-actions]

Coverage amd64

Package	Line Rate	Branch Rate	Health
include.hicr.backends.boost	75%	43%	➖
include.hicr.backends.hwloc	77%	37%	➖
include.hicr.backends.mpi	92%	52%	✔
include.hicr.backends.nosv	71%	45%	➖
include.hicr.backends.pthreads	89%	49%	✔
include.hicr.core	73%	45%	➖
include.hicr.frontends.RPCEngine	100%	49%	✔
include.hicr.frontends.channel	95%	62%	✔
include.hicr.frontends.channel.fixedSize	100%	50%	✔
include.hicr.frontends.channel.fixedSize.mpsc.locking	92%	65%	✔
include.hicr.frontends.channel.fixedSize.mpsc.nonlocking	96%	57%	✔
include.hicr.frontends.channel.fixedSize.spsc	95%	68%	✔
include.hicr.frontends.channel.variableSize	95%	50%	✔
include.hicr.frontends.channel.variableSize.mpsc.locking	84%	50%	✔
include.hicr.frontends.channel.variableSize.mpsc.nonlocking	95%	48%	✔
include.hicr.frontends.channel.variableSize.spsc	92%	60%	✔
include.hicr.frontends.objectStore	63%	41%	➖
include.hicr.frontends.tasking	80%	56%	✔
Summary	83% (1952 / 2339)	48% (1133 / 2367)	✔

Minimum allowed line rate is 60%