[API][Core] Memory Pools

[noelchalmers]

Description

Adds new occa::memoryPool object to the OCCA API, which allows users to access a pool of device memory.

The occa::memoryPool object is created from an initialized occa::device as

occa::memoryPool memPool = device.createMemoryPool(props);

After creation, the user can reserve space inside the memory pool, receiving a corresponding occa::memory object which references a reserved memory region:

occa::memory a = memPool.reserve<float>(entries);

The underlying device memory pool region managed by the occa::memoryPool is automatically resized and de-fragmented as new reservations are added. The user can query how large the underlying memory region is, and how much space is currently reserved:

udim_t  s = memPool.size();
udim_t  r = memPool.reserved();

Reservations are automatically released when all occa::memory references to a given region are deleted/freed.

The user can manually resize the underlying pool:

memPool.resize(bytes);

However, the size of the memory pool cannot be reduced below the current reservation total.

ToDo

• [ ] C bindings
• [ ] Testing for each backend in small benchmarks

[codecov[bot]]

Codecov Report

Merging #543 (8b14acb) into development (f5e4972) will increase coverage by 0.11%. The diff coverage is 71.19%.

:exclamation: Current head 8b14acb differs from pull request most recent head c001ae6. Consider uploading reports for the commit c001ae6 to get more accurate results

Additional details and impacted files

@@               Coverage Diff               @@
##           development     #543      +/-   ##
===============================================
+ Coverage        76.27%   76.38%   +0.11%     
===============================================
  Files              265      271       +6     
  Lines            19554    19833     +279     
===============================================
+ Hits             14915    15150     +235     
- Misses            4639     4683      +44     

Impacted Files	Coverage Δ
src/c/device.cpp	89.06% <0.00%> (-5.94%)	:arrow_down:
src/occa/internal/core/buffer.cpp	100.00% <ø> (ø)
src/occa/internal/core/buffer.hpp	0.00% <0.00%> (ø)
src/occa/internal/c/types.cpp	77.64% <55.00%> (-0.81%)	:arrow_down:
src/occa/internal/core/memoryPool.cpp	67.66% <67.66%> (ø)
src/core/memoryPool.cpp	68.47% <68.47%> (ø)
src/c/experimental/memoryPool.cpp	86.66% <86.66%> (ø)
include/occa/core/memoryPool.tpp	100.00% <100.00%> (ø)
src/c/base.cpp	88.17% <100.00%> (+0.96%)	:arrow_up:
src/core/base.cpp	71.57% <100.00%> (+0.61%)	:arrow_up:
... and 11 more