codon/README.md

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## What is Codon?

Codon is a high-performance Python implementation that compiles to native machine code without
any runtime overhead. Typical speedups over vanilla Python are on the order of 10-100x or more, on
a single thread. Codon's performance is typically on par with (and sometimes better than) that of
C/C++. Unlike Python, Codon supports native multithreading, which can lead to speedups many times
higher still.

*Think of Codon as Python reimagined for static, ahead-of-time compilation, built from the ground
up with best possible performance in mind.*

### Goals

- :bulb: **No learning curve:** Be as close to CPython as possible in terms of syntax, semantics and libraries
- :rocket: **Top-notch performance:** At *least* on par with low-level languages like C, C++ or Rust
- :computer: **Hardware support:** Full, seamless support for multicore programming, multithreading (no GIL!), GPU and more
- :chart_with_upwards_trend: **Optimizations:** Comprehensive optimization framework that can target high-level Python constructs
  and libraries
- :battery: **Interoperability:** Full interoperability with Python's ecosystem of packages and libraries

### Non-goals

- :x: *Drop-in replacement for CPython:* Codon is not a drop-in replacement for CPython. There are some
  aspects of Python that are not suitable for static compilation — we don't support these in Codon.
  There are ways to use Codon in larger Python codebases via its [JIT decorator](https://docs.exaloop.io/codon/interoperability/decorator)
  or [Python extension backend](https://docs.exaloop.io/codon/interoperability/pyext). Codon also supports
  calling any Python module via its [Python interoperability](https://docs.exaloop.io/codon/interoperability/python).
  See also [*"Differences with Python"*](https://docs.exaloop.io/codon/general/differences) in the docs.

- :x: *New syntax and language constructs:* We try to avoid adding new syntax, keywords or other language
  features as much as possible. While Codon does add some new syntax in a couple places (e.g. to express
  parallelism), we try to make it as familiar and intuitive as possible.

## Install

Pre-built binaries for Linux (x86_64) and macOS (x86_64 and arm64) are available alongside [each release](https://github.com/exaloop/codon/releases).
Download and install with:

```bash
/bin/bash -c "$(curl -fsSL https://exaloop.io/install.sh)"
```

Or you can [build from source](https://docs.exaloop.io/codon/advanced/build).

## Examples

Codon is a Python-compatible language, and many Python programs will work with few if any modifications:

```python
def fib(n):
    a, b = 0, 1
    while a < n:
        print(a, end=' ')
        a, b = b, a+b
    print()
fib(1000)
```

The `codon` compiler has a number of options and modes:

```bash
# compile and run the program
codon run fib.py
# 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987

# compile and run the program with optimizations enabled
codon run -release fib.py
# 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987

# compile to executable with optimizations enabled
codon build -release -exe fib.py
./fib
# 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987

# compile to LLVM IR file with optimizations enabled
codon build -release -llvm fib.py
# outputs file fib.ll
```

See [the docs](https://docs.exaloop.io/codon/general/intro) for more options and examples.

You can import and use any Python package from Codon. For example:

```python
from python import matplotlib.pyplot as plt
data = [x**2 for x in range(10)]
plt.plot(data)
plt.show()
```

(Just remember to set the `CODON_PYTHON` environment variable to the CPython shared library,
as explained in the [the docs](https://docs.exaloop.io/codon/interoperability/python).)

This prime counting example showcases Codon's [OpenMP](https://www.openmp.org/) support, enabled
with the addition of one line. The `@par` annotation tells the compiler to parallelize the
following `for`-loop, in this case using a dynamic schedule, chunk size of 100, and 16 threads.

```python
from sys import argv

def is_prime(n):
    factors = 0
    for i in range(2, n):
        if n % i == 0:
            factors += 1
    return factors == 0

limit = int(argv[1])
total = 0

@par(schedule='dynamic', chunk_size=100, num_threads=16)
for i in range(2, limit):
    if is_prime(i):
        total += 1

print(total)
```

Codon supports writing and executing GPU kernels. Here's an example that computes the
[Mandelbrot set](https://en.wikipedia.org/wiki/Mandelbrot_set):

```python
import gpu

MAX    = 1000  # maximum Mandelbrot iterations
N      = 4096  # width and height of image
pixels = [0 for _ in range(N * N)]

def scale(x, a, b):
    return a + (x/N)*(b - a)

@gpu.kernel
def mandelbrot(pixels):
    idx = (gpu.block.x * gpu.block.dim.x) + gpu.thread.x
    i, j = divmod(idx, N)
    c = complex(scale(j, -2.00, 0.47), scale(i, -1.12, 1.12))
    z = 0j
    iteration = 0

    while abs(z) <= 2 and iteration < MAX:
        z = z**2 + c
        iteration += 1

    pixels[idx] = int(255 * iteration/MAX)

mandelbrot(pixels, grid=(N*N)//1024, block=1024)
```

GPU programming can also be done using the `@par` syntax with `@par(gpu=True)`.

## Documentation

Please see [docs.exaloop.io](https://docs.exaloop.io/codon) for in-depth documentation.