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libmir / mir-glas

[Experimental] LLVM-accelerated Generic Linear Algebra Subprograms
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algebra blas glas lapack linear-algebra-subprograms matrix matrix-multiplication simd

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glas

LLVM-accelerated Generic Linear Algebra Subprograms (GLAS)

Description

GLAS is a C library written in Dlang. No C++/D runtime is required but libc, which is available everywhere.

The library provides

  1. BLAS (Basic Linear Algebra Subprograms) API.
  2. GLAS (Generic Linear Algebra Subprograms) API.

CBLAS API can be provided by linking with Netlib's CBLAS library.

dub

GLAS can be used with DMD and LDC but LDC (LLVM D Compiler) >= 1.1.0 beta 6 should be installed in common path anyway.

Note performance issue https://github.com/libmir/mir-glas/issues/18.

GLAS can be included automatically in a project using dub (the D package manager). DUB will build GLAS and CPUID manually with LDC.

{
   ...
   "dependencies": {
      "mir-glas": "~><current_mir-glas_version>",
      "mir-cpuid": "~><current_mir-cpuid_version>"
   },
   "lflags": ["-L$MIR_GLAS_PACKAGE_DIR", "-L$MIR_CPUID_PACKAGE_DIR"]
}

$MIR_GLAS_PACKAGE_DIR and $MIR_CPUID_PACKAGE_DIR will be replaced automatically by DUB to appropriate directories.

Usage

mir-glas can be used like a common C library. It should be linked with mir-cpuid. A compiler, for example GCC, may require mir-cpuid to be passed after mir-glas: -lmir-glas -lmir-cpuid.

GLAS API

GLAS API is based on the new ndslice from mir-algorithm. Other languages can use simple structure definition. Examples are available for C and for Dlang.

Headers

C/C++ headers are located in include/. D headers are located in source/.

There are two files:

  1. glas/fortran.h / glas/fortran.d - for Netilb's BLAS API
  2. glas/ndslice.h / glas/ndslice.d - for GLAS API

Manual Compilation

Compiler installation

LDC (LLVM D Compiler) >= 1.1.0 beta 6 is required to build a project. You may want to build LDC from source or use LDC 1.1.0 beta 6. Beta 2 generates a lot of warnings that can be ignored. Beta 3 is not supported.

LDC binaries contains two compilers: ldc2 and ldmd2. It is recommended to use ldmd2 with mir-glas.

Recent LDC packages come with the dub package manager. dub is used to build the project.

Mir CPUID

Mir CPUID is CPU Identification Routines.

Download mir-cpuid

dub fetch mir-cpuid --cache=local

Change the directory

cd mir-cpuid-<current-mir-cpuid-version>/mir-cpuid

Build mir-cpuid

dub build --build=release-nobounds --compiler=ldmd2 --build-mode=singleFile --parallel --force

You may need to add --arch=x86_64, if you use windows.

Copy libmir-cpuid.a to your project or add its directory to the library path.

Mir GLAS

Download mir-glas

dub fetch mir-glas --cache=local

Change the directory

cd mir-glas-<current-mir-glas-version>/mir-glas

Build mir-glas

dub build --config=static --build=target-native --compiler=ldmd2 --build-mode=singleFile --parallel --force

You may need to add --arch=x86_64 if you use windows.

Copy libmir-glas.a to your project or add its directory to the library path.

Status

We are open for contributing! The hardest part (GEMM) is already implemented.

Porting to a new target

Five steps

  1. Implement cpuid_init function for mir-cpuid. This function should be implemented per platform or OS. Already implemented targets are
    • x86, any OS
    • x86_64, any OS
  2. Verify that source/glas/internal/memory.d contains an implementation for the OS. Already implemented targets are
    • Posix (Linux, macOS, and others)
    • Windows
  3. Add new configuration for register blocking to source/glas/internal/config.d. Already implemented configuration available for
    • x87
    • SSE2
    • AVX / AVX2
    • AVX512 (requires LLVM bug fixes).
  4. Create a Pool Request.
  5. Coordinate with LDC team in case of compiler bugs.

Questions & Answers

Why GLAS is called "Generic ..."?

  1. GLAS has a generic internal implementation, which can be easily ported to any other architecture with minimal efforts (5 minutes).
  2. GLAS API provides more functionality comparing with BLAS.
  3. It is written in Dlang using generic programming.

Why it is better then other BLAS Open Source Libraries like OpenBLAS and Eigen?

  1. GLAS is faster.
  2. GLAS API is more user-friendly and does not require additional data copying.
  3. GLAS does not require C++ runtime comparing with Eigen.
  4. GLAS does not require platform specific optimizations like Eigen intrinsics micro kernels and OpenBLAS assembler macro kernels.
  5. GLAS has a simple implementation, which can be easily ported and extended.

Why GLAS does not have Lazy Evaluation and Aliasing like Eigen?

GLAS is a lower level library than Eigen. For example, GLAS can be an Eigen BLAS back-end in the future Lazy Evaluation and Aliasing can be easily implemented in D. Explicit composition of operations can be done using mir.ndslice.algorithm and multidimensional map from mir.ndslice.topology, which is a generic way to perform any lazy operations you want.