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Use proper atomics for ParILU(T) and ParIC(T) #1434

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@upsj upsj commented Oct 16, 2023

I was always a bit surprised by the large discrepancy between OpenMP and GPU ParILU(T) convergence. Recently I found out why that is: GPUs don't have coherent L1 caches, so the current implementation of ParILU (without any memory fences that might cause L1 cache flushes) may read stale values instead of the latest values. This is not an issue on x86 CPUs, because they have a fully coherent cache hierarchy. By replacing the regular (weak) loads/stores by relaxed loads/stores, we get more up-to-date values.

In some preliminary experiments, this reduced the number of iterations to reach a threshold by at least a factor 2.

Before merging, I'll attach some benchmarks to evaluate the runtime impact of these changes.

@upsj upsj added the 1:ST:ready-for-review This PR is ready for review label Oct 16, 2023
@upsj upsj requested a review from a team October 16, 2023 11:52
@upsj upsj self-assigned this Oct 16, 2023
@ginkgo-bot ginkgo-bot added mod:cuda This is related to the CUDA module. mod:hip This is related to the HIP module. type:factorization This is related to the Factorizations labels Oct 16, 2023
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async jacobi can also use this atomic rather than __threadfence();
async jacobi use __threadfence or not affect the convergence much, too

@yhmtsai yhmtsai requested a review from a team October 16, 2023 15:33
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All modified and coverable lines are covered by tests ✅

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LGTM!

@upsj upsj added 1:ST:ready-to-merge This PR is ready to merge. and removed 1:ST:ready-for-review This PR is ready for review labels Nov 3, 2023
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upsj commented Nov 3, 2023

I'm seeing a slight decrease in time-to-solution on the ani* matrices with BiCGStab and ParILUT (and an even slighter reduction with ParILU) due to the higher preconditioner quality, despite the runtime of the sweeps increasing by 1.05x (ParILUT) and 1.45x (ParILU).
On the largest problem (ani7), the time-to-solution is reduced from 11.6 s to 10.2s, mostly due to the reduced number of iterations (73 vs. 84).

So from my perspective, this PR is good to go :)

@upsj upsj added this to the Release 1.7.0 milestone Nov 3, 2023
@upsj upsj merged commit eea1dd6 into develop Nov 3, 2023
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@upsj upsj deleted the par_ilu_convergence branch November 3, 2023 20:52
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@tcojean tcojean mentioned this pull request Nov 6, 2023
tcojean added a commit that referenced this pull request Nov 10, 2023
Release 1.7.0 to master

The Ginkgo team is proud to announce the new Ginkgo minor release 1.7.0. This release brings new features such as:
- Complete GPU-resident sparse direct solvers feature set and interfaces,
- Improved Cholesky factorization performance,
- A new MC64 reordering,
- Batched iterative solver support with the BiCGSTAB solver with batched Dense and ELL matrix types,
- MPI support for the SYCL backend,
- Improved ParILU(T)/ParIC(T) preconditioner convergence,
and more!

If you face an issue, please first check our [known issues page](https://github.com/ginkgo-project/ginkgo/wiki/Known-Issues) and the [open issues list](https://github.com/ginkgo-project/ginkgo/issues) and if you do not find a solution, feel free to [open a new issue](https://github.com/ginkgo-project/ginkgo/issues/new/choose) or ask a question using the [github discussions](https://github.com/ginkgo-project/ginkgo/discussions).

Supported systems and requirements:
+ For all platforms, CMake 3.16+
+ C++14 compliant compiler
+ Linux and macOS
  + GCC: 5.5+
  + clang: 3.9+
  + Intel compiler: 2019+
  + Apple Clang: 14.0 is tested. Earlier versions might also work.
  + NVHPC: 22.7+
  + Cray Compiler: 14.0.1+
  + CUDA module: CMake 3.18+, and CUDA 10.1+ or NVHPC 22.7+
  + HIP module: ROCm 4.5+
  + DPC++ module: Intel oneAPI 2022.1+ with oneMKL and oneDPL. Set the CXX compiler to `dpcpp` or `icpx`.
  + MPI: standard version 3.1+, ideally GPU Aware, for best performance
+ Windows
  + MinGW: GCC 5.5+
  + Microsoft Visual Studio: VS 2019+
  + CUDA module: CUDA 10.1+, Microsoft Visual Studio
  + OpenMP module: MinGW.

### Version support changes

+ CUDA 9.2 is no longer supported and 10.0 is untested [#1382](#1382)
+ Ginkgo now requires CMake version 3.16 (and 3.18 for CUDA) [#1368](#1368)

### Interface changes

+ `const` Factory parameters can no longer be modified through `with_*` functions, as this breaks const-correctness [#1336](#1336) [#1439](#1439)

### New Deprecations

+ The `device_reset` parameter of CUDA and HIP executors no longer has an effect, and its `allocation_mode` parameters have been deprecated in favor of the `Allocator` interface. [#1315](#1315)
+ The CMake parameter `GINKGO_BUILD_DPCPP` has been deprecated in favor of `GINKGO_BUILD_SYCL`. [#1350](#1350)
+ The `gko::reorder::Rcm` interface has been deprecated in favor of `gko::experimental::reorder::Rcm` based on `Permutation`. [#1418](#1418)
+ The Permutation class' `permute_mask` functionality. [#1415](#1415)
+ Multiple functions with typos (`set_complex_subpsace()`, range functions such as `conj_operaton` etc). [#1348](#1348)

### Summary of previous deprecations
+ `gko::lend()` is not necessary anymore.
+ The classes `RelativeResidualNorm` and `AbsoluteResidualNorm` are deprecated in favor of `ResidualNorm`.
+ The class `AmgxPgm` is deprecated in favor of `Pgm`.
+ Default constructors for the CSR `load_balance` and `automatical` strategies
+ The PolymorphicObject's move-semantic `copy_from` variant
+ The templated `SolverBase` class.
+ The class `MachineTopology` is deprecated in favor of `machine_topology`.
+ Logger constructors and create functions with the `executor` parameter.
+ The virtual, protected, Dense functions `compute_norm1_impl`, `add_scaled_impl`, etc.
+ Logger events for solvers and criterion without the additional `implicit_tau_sq` parameter.
+ The global `gko::solver::default_krylov_dim`, use instead `gko::solver::gmres_default_krylov_dim`.

### Added features

+ Adds a batch::BatchLinOp class that forms a base class for batched linear operators such as batched matrix formats, solver and preconditioners [#1379](#1379)
+ Adds a batch::MultiVector class that enables operations such as dot, norm, scale on batched vectors [#1371](#1371)
+ Adds a batch::Dense matrix format that stores batched dense matrices and provides gemv operations for these dense matrices. [#1413](#1413)
+ Adds a batch::Ell matrix format that stores batched Ell matrices and provides spmv operations for these batched Ell matrices. [#1416](#1416) [#1437](#1437)
+ Add a batch::Bicgstab solver (class, core, and reference kernels) that enables iterative solution of batched linear systems [#1438](#1438).
+ Add device kernels (CUDA, HIP, and DPCPP) for batch::Bicgstab solver. [#1443](#1443).
+ New MC64 reordering algorithm which optimizes the diagonal product or sum of a matrix by permuting the rows, and computes additional scaling factors for equilibriation [#1120](#1120)
+ New interface for (non-symmetric) permutation and scaled permutation of Dense and Csr matrices [#1415](#1415)
+ LU and Cholesky Factorizations can now be separated into their factors [#1432](#1432)
+ New symbolic LU factorization algorithm that is optimized for matrices with an almost-symmetric sparsity pattern [#1445](#1445)
+ Sorting kernels for SparsityCsr on all backends [#1343](#1343)
+ Allow passing pre-generated local solver as factory parameter for the distributed Schwarz preconditioner [#1426](#1426)
+ Add DPCPP kernels for Partition [#1034](#1034), and CSR's `check_diagonal_entries` and `add_scaled_identity` functionality [#1436](#1436)
+ Adds a helper function to create a partition based on either local sizes, or local ranges [#1227](#1227)
+ Add function to compute arithmetic mean of dense and distributed vectors [#1275](#1275)
+ Adds `icpx` compiler supports [#1350](#1350)
+ All backends can be built simultaneously [#1333](#1333)
+ Emits a CMake warning in downstream projects that use different compilers than the installed Ginkgo [#1372](#1372)
+ Reordering algorithms in sparse_blas benchmark [#1354](#1354)
+ Benchmarks gained an `-allocator` parameter to specify device allocators [#1385](#1385)
+ Benchmarks gained an `-input_matrix` parameter that initializes the input JSON based on the filename [#1387](#1387)
+ Benchmark inputs can now be reordered as a preprocessing step [#1408](#1408)


### Improvements

+ Significantly improve Cholesky factorization performance [#1366](#1366)
+ Improve parallel build performance [#1378](#1378)
+ Allow constrained parallel test execution using CTest resources [#1373](#1373)
+ Use arithmetic type more inside mixed precision ELL [#1414](#1414)
+ Most factory parameters of factory type no longer need to be constructed explicitly via `.on(exec)` [#1336](#1336) [#1439](#1439)
+ Improve ParILU(T)/ParIC(T) convergence by using more appropriate atomic operations [#1434](#1434)

### Fixes

+ Fix an over-allocation for OpenMP reductions [#1369](#1369)
+ Fix DPCPP's common-kernel reduction for empty input sizes [#1362](#1362)
+ Fix several typos in the API and documentation [#1348](#1348)
+ Fix inconsistent `Threads` between generations [#1388](#1388)
+ Fix benchmark median condition [#1398](#1398)
+ Fix HIP 5.6.0 compilation [#1411](#1411)
+ Fix missing destruction of rand_generator from cuda/hip [#1417](#1417)
+ Fix PAPI logger destruction order [#1419](#1419)
+ Fix TAU logger compilation [#1422](#1422)
+ Fix relative criterion to not iterate if the residual is already zero [#1079](#1079)
+ Fix memory_order invocations with C++20 changes [#1402](#1402)
+ Fix `check_diagonal_entries_exist` report correctly when only missing diagonal value in the last rows. [#1440](#1440)
+ Fix checking OpenMPI version in cross-compilation settings [#1446](#1446)
+ Fix false-positive deprecation warnings in Ginkgo, especially for the old Rcm (it doesn't emit deprecation warnings anymore as a result but is still considered deprecated) [#1444](#1444)


### Related PR: #1451
tcojean added a commit that referenced this pull request Nov 10, 2023
Release 1.7.0 to develop

The Ginkgo team is proud to announce the new Ginkgo minor release 1.7.0. This release brings new features such as:
- Complete GPU-resident sparse direct solvers feature set and interfaces,
- Improved Cholesky factorization performance,
- A new MC64 reordering,
- Batched iterative solver support with the BiCGSTAB solver with batched Dense and ELL matrix types,
- MPI support for the SYCL backend,
- Improved ParILU(T)/ParIC(T) preconditioner convergence,
and more!

If you face an issue, please first check our [known issues page](https://github.com/ginkgo-project/ginkgo/wiki/Known-Issues) and the [open issues list](https://github.com/ginkgo-project/ginkgo/issues) and if you do not find a solution, feel free to [open a new issue](https://github.com/ginkgo-project/ginkgo/issues/new/choose) or ask a question using the [github discussions](https://github.com/ginkgo-project/ginkgo/discussions).

Supported systems and requirements:
+ For all platforms, CMake 3.16+
+ C++14 compliant compiler
+ Linux and macOS
  + GCC: 5.5+
  + clang: 3.9+
  + Intel compiler: 2019+
  + Apple Clang: 14.0 is tested. Earlier versions might also work.
  + NVHPC: 22.7+
  + Cray Compiler: 14.0.1+
  + CUDA module: CMake 3.18+, and CUDA 10.1+ or NVHPC 22.7+
  + HIP module: ROCm 4.5+
  + DPC++ module: Intel oneAPI 2022.1+ with oneMKL and oneDPL. Set the CXX compiler to `dpcpp` or `icpx`.
  + MPI: standard version 3.1+, ideally GPU Aware, for best performance
+ Windows
  + MinGW: GCC 5.5+
  + Microsoft Visual Studio: VS 2019+
  + CUDA module: CUDA 10.1+, Microsoft Visual Studio
  + OpenMP module: MinGW.

### Version support changes

+ CUDA 9.2 is no longer supported and 10.0 is untested [#1382](#1382)
+ Ginkgo now requires CMake version 3.16 (and 3.18 for CUDA) [#1368](#1368)

### Interface changes

+ `const` Factory parameters can no longer be modified through `with_*` functions, as this breaks const-correctness [#1336](#1336) [#1439](#1439)

### New Deprecations

+ The `device_reset` parameter of CUDA and HIP executors no longer has an effect, and its `allocation_mode` parameters have been deprecated in favor of the `Allocator` interface. [#1315](#1315)
+ The CMake parameter `GINKGO_BUILD_DPCPP` has been deprecated in favor of `GINKGO_BUILD_SYCL`. [#1350](#1350)
+ The `gko::reorder::Rcm` interface has been deprecated in favor of `gko::experimental::reorder::Rcm` based on `Permutation`. [#1418](#1418)
+ The Permutation class' `permute_mask` functionality. [#1415](#1415)
+ Multiple functions with typos (`set_complex_subpsace()`, range functions such as `conj_operaton` etc). [#1348](#1348)

### Summary of previous deprecations
+ `gko::lend()` is not necessary anymore.
+ The classes `RelativeResidualNorm` and `AbsoluteResidualNorm` are deprecated in favor of `ResidualNorm`.
+ The class `AmgxPgm` is deprecated in favor of `Pgm`.
+ Default constructors for the CSR `load_balance` and `automatical` strategies
+ The PolymorphicObject's move-semantic `copy_from` variant
+ The templated `SolverBase` class.
+ The class `MachineTopology` is deprecated in favor of `machine_topology`.
+ Logger constructors and create functions with the `executor` parameter.
+ The virtual, protected, Dense functions `compute_norm1_impl`, `add_scaled_impl`, etc.
+ Logger events for solvers and criterion without the additional `implicit_tau_sq` parameter.
+ The global `gko::solver::default_krylov_dim`, use instead `gko::solver::gmres_default_krylov_dim`.

### Added features

+ Adds a batch::BatchLinOp class that forms a base class for batched linear operators such as batched matrix formats, solver and preconditioners [#1379](#1379)
+ Adds a batch::MultiVector class that enables operations such as dot, norm, scale on batched vectors [#1371](#1371)
+ Adds a batch::Dense matrix format that stores batched dense matrices and provides gemv operations for these dense matrices. [#1413](#1413)
+ Adds a batch::Ell matrix format that stores batched Ell matrices and provides spmv operations for these batched Ell matrices. [#1416](#1416) [#1437](#1437)
+ Add a batch::Bicgstab solver (class, core, and reference kernels) that enables iterative solution of batched linear systems [#1438](#1438).
+ Add device kernels (CUDA, HIP, and DPCPP) for batch::Bicgstab solver. [#1443](#1443).
+ New MC64 reordering algorithm which optimizes the diagonal product or sum of a matrix by permuting the rows, and computes additional scaling factors for equilibriation [#1120](#1120)
+ New interface for (non-symmetric) permutation and scaled permutation of Dense and Csr matrices [#1415](#1415)
+ LU and Cholesky Factorizations can now be separated into their factors [#1432](#1432)
+ New symbolic LU factorization algorithm that is optimized for matrices with an almost-symmetric sparsity pattern [#1445](#1445)
+ Sorting kernels for SparsityCsr on all backends [#1343](#1343)
+ Allow passing pre-generated local solver as factory parameter for the distributed Schwarz preconditioner [#1426](#1426)
+ Add DPCPP kernels for Partition [#1034](#1034), and CSR's `check_diagonal_entries` and `add_scaled_identity` functionality [#1436](#1436)
+ Adds a helper function to create a partition based on either local sizes, or local ranges [#1227](#1227)
+ Add function to compute arithmetic mean of dense and distributed vectors [#1275](#1275)
+ Adds `icpx` compiler supports [#1350](#1350)
+ All backends can be built simultaneously [#1333](#1333)
+ Emits a CMake warning in downstream projects that use different compilers than the installed Ginkgo [#1372](#1372)
+ Reordering algorithms in sparse_blas benchmark [#1354](#1354)
+ Benchmarks gained an `-allocator` parameter to specify device allocators [#1385](#1385)
+ Benchmarks gained an `-input_matrix` parameter that initializes the input JSON based on the filename [#1387](#1387)
+ Benchmark inputs can now be reordered as a preprocessing step [#1408](#1408)


### Improvements

+ Significantly improve Cholesky factorization performance [#1366](#1366)
+ Improve parallel build performance [#1378](#1378)
+ Allow constrained parallel test execution using CTest resources [#1373](#1373)
+ Use arithmetic type more inside mixed precision ELL [#1414](#1414)
+ Most factory parameters of factory type no longer need to be constructed explicitly via `.on(exec)` [#1336](#1336) [#1439](#1439)
+ Improve ParILU(T)/ParIC(T) convergence by using more appropriate atomic operations [#1434](#1434)

### Fixes

+ Fix an over-allocation for OpenMP reductions [#1369](#1369)
+ Fix DPCPP's common-kernel reduction for empty input sizes [#1362](#1362)
+ Fix several typos in the API and documentation [#1348](#1348)
+ Fix inconsistent `Threads` between generations [#1388](#1388)
+ Fix benchmark median condition [#1398](#1398)
+ Fix HIP 5.6.0 compilation [#1411](#1411)
+ Fix missing destruction of rand_generator from cuda/hip [#1417](#1417)
+ Fix PAPI logger destruction order [#1419](#1419)
+ Fix TAU logger compilation [#1422](#1422)
+ Fix relative criterion to not iterate if the residual is already zero [#1079](#1079)
+ Fix memory_order invocations with C++20 changes [#1402](#1402)
+ Fix `check_diagonal_entries_exist` report correctly when only missing diagonal value in the last rows. [#1440](#1440)
+ Fix checking OpenMPI version in cross-compilation settings [#1446](#1446)
+ Fix false-positive deprecation warnings in Ginkgo, especially for the old Rcm (it doesn't emit deprecation warnings anymore as a result but is still considered deprecated) [#1444](#1444)

### Related PR: #1454
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