Arraymancer - A n-dimensional tensor (ndarray) library.

Arraymancer is a tensor (N-dimensional array) project in Nim. The main focus is providing a fast and ergonomic CPU and GPU ndarray library on which to build a scientific computing and in particular a deep learning ecosystem.

The library is inspired by Numpy and PyTorch. The library provides ergonomics very similar to Numpy, Julia and Matlab but is fully parallel and significantly faster than those libraries. It is also faster than C-based Torch.

Note: While Nim is compiled and does not offer an interactive REPL yet (like Jupyter), it allows much faster prototyping than C++ due to extremely fast compilation times. Arraymancer compiles in about 5 seconds on my dual-core MacBook.

4 reasons why Arraymancer

The Python community is struggling to bring Numpy up-to-speed

Numba JIT compiler
Dask delayed parallel computation graph
Cython to ease numerical computations in Python
Due to the GIL shared-memory parallelism (OpenMP) is not possible in pure Python
Use "vectorized operations" (i.e. don't use for loops in Python)

Why not use in a single language with all the blocks to build the most efficient scientific computing library with Python ergonomics.

OpenMP batteries included.

A researcher workflow is a fight against inefficiencies

Researchers in a heavy scientific computing domain often have the following workflow: Mathematica/Matlab/Python/R (prototyping) -> C/C++/Fortran (speed, memory)

Why not use in a language as productive as Python and as fast as C? Code once, and don't spend months redoing the same thing at a lower level.

Tools available in labs are not available in production:

Managing and deploying Python (2.7, 3.5, 3.6) and packages version in a robust manner requires devops-fu (virtualenv, Docker, ...)
Python data science ecosystem does not run on embedded devices (Nvidia Tegra/drones) or mobile phones, especially preprocessing dependencies.

Bridging the gap between deep learning research and production

The deep learning frameworks are currently in two camps:

Research: Theano, Tensorflow, Keras, Torch, PyTorch
Production: Caffe, Darknet, (Tensorflow)

Furthermore, Python preprocessing steps, unless using OpenCV, often needs a custom implementation (think text/speech preprocessing on phones).

Tensorflow is supposed to bridge the gap between research and production but its syntax and ergonomics are a pain to work with. It's the same issue as researchers, "Prototype in Keras, and when you need low-level --> Tensorflow".
Deployed models are static, there is no interface to add a new observation/training sample to any framework, the end goal being to use a model as a webservice.

So why Arraymancer ?

All those pain points may seem like a huge undertaking however thanks to the Nim language, we can have Arraymancer:

Be as fast as C
Accelerated routines with Intel MKL/OpenBLAS or even NNPACK
Access to CUDA and CuDNN and generate custom CUDA kernels on the fly via metaprogramming.
A Python-like syntax with custom operators a * b for tensor multiplication instead of a.dot(b) (Numpy/Tensorflow) or a.mm(b) (Torch)
Numpy-like slicing ergonomics t[0..4, 2..10|2]
For everything that Nim doesn't have yet, you can use Nim bindings to C, C++, Objective-C or Javascript to bring it to Nim. Nim also has unofficial Python->Nim and Nim->Python wrappers.

Future ambitions

Because apparently to be successful you need a vision, I would like Arraymancer to be:

The go-to tool for Deep Learning video processing. I.e. vid = load_video("./cats/youtube_cat_video.mkv")
Target javascript, WebAssembly, Apple Metal, ARM devices, AMD Rocm, OpenCL, you name it.
Target cryptominers FPGAs because they drove the price of GPUs for honest deep-learners too high.
The base of a Starcraft II AI bot.

Installation:

Nim is available in some Linux repositories and on Homebrew for macOS.

I however recommend installing Nim in your user profile via choosenim. Once choosenim installed Nim, you can nimble install arraymancer which will pull arraymancer and all its dependencies.

Full documentation

Detailed API is available on Arraymancer official documentation.

Features

For now Arraymancer is mostly at the ndarray stage, a vision package and a deep learning demo are available with logistic regression and perceptron from scratch.

You can also check the detailed example or benchmark perceptron for a preview of Arraymancer deep learning usage.

Available autograd and neural networks features are detailed in the technical reference part of the documentation.

Arraymancer in action

Arraymancer tutorial is available here.

Here is a preview of Arraymancer syntax.

Tensor creation and slicing

import math, arraymancer, future

const
    x = @[1, 2, 3, 4, 5]
    y = @[1, 2, 3, 4, 5]

var
    vandermonde: seq[seq[int]]
    row: seq[int]

vandermonde = newSeq[seq[int]]()

for i, xx in x:
    row = newSeq[int]()
    vandermonde.add(row)
    for j, yy in y:
        vandermonde[i].add(xx^yy)

let foo = vandermonde.toTensor()

echo foo

# Tensor of shape 5x5 of type "int" on backend "Cpu"
# |1      1       1       1       1|
# |2      4       8       16      32|
# |3      9       27      81      243|
# |4      16      64      256     1024|
# |5      25      125     625     3125|

echo foo[1..2, 3..4] # slice

# Tensor of shape 2x2 of type "int" on backend "Cpu"
# |16     32|
# |81     243|

Reshaping and concatenation

import ../arraymancer, sequtils


let a = toSeq(1..4).toTensor(Cpu).reshape(2,2)

let b = toSeq(5..8).toTensor(Cpu).reshape(2,2)

let c = toSeq(11..16).toTensor(Cpu)
let c0 = c.reshape(3,2)
let c1 = c.reshape(2,3)

echo concat(a,b,c0, axis = 0)
# Tensor of shape 7x2 of type "int" on backend "Cpu"
# |1      2|
# |3      4|
# |5      6|
# |7      8|
# |11     12|
# |13     14|
# |15     16|

echo concat(a,b,c1, axis = 1)
# Tensor of shape 2x7 of type "int" on backend "Cpu"
# |1      2       5       6       11      12      13|
# |3      4       7       8       14      15      16|

Broadcasting

Image from Scipy

let j = [0, 10, 20, 30].toTensor(Cpu).reshape(4,1)
let k = [0, 1, 2].toTensor(Cpu).reshape(1,3)

echo j .+ k
# Tensor of shape 4x3 of type "int" on backend "Cpu"
# |0      1       2|
# |10     11      12|
# |20     21      22|
# |30     31      32|

Tensors on CPU and on Cuda

Tensors and CudaTensors do not have the same features implemented yet. Also Cuda Tensors can only be float32 or float64 while Cpu Tensor can be integers, string, boolean or any custom object.

Here is a comparative table, not that this feature set is developing very rapidly.

Action	Tensor	CudaTensor
Accessing tensor properties	[x]	[x]
Tensor creation	[x]	by converting a cpu Tensor
Accessing or modifying a single value	[x]	[]
Iterating on a Tensor	[x]	[]
Slicing a Tensor	[x]	[x]
Slice mutation `a[1,_] = 10`	[x]	[]
Comparison `==`	[x]	Coming soon
Element-wise basic operations	[x]	[x]
Universal functions	[x]	[x]
Automatically broadcasted operations	[x]	Coming soon
Matrix-Matrix and Matrix-Vector multiplication	[x]	[x] Note that sliced CudaTensors must explicitly be made contiguous for the moment
Displaying a tensor	[x]	[x]
Higher-order functions (map, apply, reduce, fold)	[x]	Apply, but only internally
Transposing	[x]	[x]
Converting to contiguous	[x]	[x]
Reshaping	[x]	[]
Explicit broadcast	[x]	Coming soon
Permuting dimensions	[x]	Coming soon
Concatenating tensors along existing dimension	[x]	[]
Squeezing singleton dimension	[x]	Coming soon
Slicing + squeezing	[x]	Coming soon

Speed

Arraymancer is fast, how it achieves its speed under the hood is detailed here.

Micro benchmark: Int64 matrix multiplication

Integers seem to be the abandoned children of ndarrays and tensors libraries. Everyone is optimising the hell of floating points. Not so with Arraymancer:

Archlinux, E3-1230v5 (Skylake quad-core 3.4 GHz, turbo 3.8)
Input 1500x1500 random large int64 matrix
Arraymancer 0.2.90 (master branch 2017-10-10)

Language	Speed	Memory
Nim 0.17.3 (devel) + OpenMP	0.36s	55.5 MB
Julia v0.6.0	3.11s	207.6 MB
Python 3.6.2 + Numpy 1.12 compiled from source	8.03s	58.9 MB

MacOS + i5-5257U (Broadwell dual-core mobile 2.7GHz, turbo 3.1)
Input 1500x1500 random large int64 matrix
Arraymancer 0.2.90 (master branch 2017-10-31)

no OpenMP compilation: nim c -d:native -d:release --out:bin/integer_matmul --nimcache:./nimcache benchmarks/integer_matmul.nim
with OpenMP: nim c -d:openmp --cc:gcc --gcc.exe:"/usr/local/bin/gcc-6" --gcc.linkerexe:"/usr/local/bin/gcc-6"  -d:native -d:release --out:bin/integer_matmul --nimcache:./nimcache benchmarks/integer_matmul.nim

Language	Speed	Memory
Nim 0.18.0 (devel) - GCC 6 + OpenMP	0.95s	71.9 MB
Nim 0.18.0 (devel) - Apple Clang 9 - no OpenMP	1.73s	71.7 MB
Julia v0.6.0	4.49s	185.2 MB
Python 3.5.2 + Numpy 1.12	9.49s	55.8 MB

Benchmark setup is in the ./benchmarks folder and similar to (stolen from) Kostya's. Note: Arraymancer float matmul is as fast as Julia Native Thread.

Logistic regression

On the demo benchmark, Arraymancer is faster than Torch in v0.2.90.

CPU

Framework	Backend	Forward+Backward Pass Time
Arraymancer v0.2.90	OpenMP + MKL	0.458ms
Torch7	MKL	0.686ms
Numpy	MKL	0.723ms

GPU

Framework	Backend	Forward+Backward Pass Time
Arraymancer v0.2.90	Cuda	WIP
Torch7	Cuda	0.286ms

DNN - 3 hidden layers

CPU

Framework	Backend	Forward+Backward Pass Time
Arraymancer v0.2.90	OpenMP + MKL	2.907ms
PyTorch	MKL	6.797ms

GPU

Framework	Backend	Forward+Backward Pass Time
Arraymancer v0.2.90	Cuda	WIP
PyTorch	Cuda	4.765ms

Intel(R) Core(TM) i7-3770K CPU @ 3.50GHz, gcc 7.2.0, MKL 2017.17.0.4.4, OpenBLAS 0.2.20, Cuda 8.0.61, Geforce GTX 1080 Ti, Nim 0.18.0

In the future, Arraymancer will leverage Nim compiler to automatically fuse operations like alpha A*B + beta C or a combination of element-wise operations. This is already done to fuse toTensor and reshape.

cooldome / Arraymancer