Add pypy example

Author: gjbex

source-code/README.md

@@ -36,3 +36,4 @@ to create it.  There is some material not covered in the presentation as well.
 1. `pyspark`: illustrations of using PySpark.
 1. `hdf5`: examples of parallel I/O using HDF5.
 1. `numpy-scipy`: some numpy/scipy codes for benchmakring.
+1. `pypy`: code to experiment with the Pypy interpreter.

source-code/pypy/README.md

@@ -0,0 +1,17 @@
+# Pypy
+
+Pypy is an alternative interpreter that can in some circumtatnces be
+up to four times faster than CPython.
+
+
+## What is it?
+
+1. `julia_set.py`: compute the Julia set.
+
+
+## How to use?
+
+To run with Pypy, use:
+```bash
+$ pypy julia_set.py 1000 > julia.txt
+```

source-code/pypy/environment.yml

@@ -0,0 +1,7 @@
+name: pypy
+channels:
+  - defaults
+dependencies:
+  - pypy
+  - numpy
+prefix: /home/gjb/miniconda3/envs/pypy

source-code/pypy/julia_set.py

@@ -0,0 +1,36 @@
+#!/usr/bin/env python
+
+import argparse
+import numpy as np
+import sys
+import time
+
+
+def julia_set_iteration(z, c):
+    i = 0
+    while i < 255 and abs(z) < 2.0:
+        z = z**2 + c
+        i += 1
+    return i
+
+def julia_set(n, c):
+    result = np.empty((n, n), dtype=np.uint8)
+    delta = 2.0*1.8/n
+    for i in range(n):
+        z_re = -1.8 + i*delta
+        for j in range(n):
+            z_im = -1.8 + j*delta
+            result[i, j] = julia_set_iteration(complex(z_re, z_im), c)
+    return result
+
+
+if __name__ == '__main__':
+    arg_parser = argparse.ArgumentParser(description='compute JUlia set')
+    arg_parser.add_argument('n', type=int, help='number of points')
+    options = arg_parser.parse_args()
+    c = complex(0.4, 0.6)
+    start = time.time()
+    julia = julia_set(options.n, c)
+    end = time.time()
+    print(f'compute time: {end - start} s', file=sys.stderr)
+    np.savetxt(sys.stdout, julia)