Created gh-images branch for storing images

file-cost.py

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+#!/usr/bin/env python
+
+import matplotlib
+matplotlib.use('SVG')
+import matplotlib.pyplot as plt
+import numpy as np
+
+matplotlib.rc('font', family='sans-serif', size=11)
+matplotlib.rc('axes', titlesize='medium', labelsize='medium')
+matplotlib.rc('xtick', labelsize='small')
+matplotlib.rc('ytick', labelsize='small')
+
+fig, ax = plt.subplots(figsize=(6, 3.5))
+ax.set_title('File storage cost')
+
+# multiplicative cost of inline files
+def inline_cost(n, B):
+    #return 4+n-n
+    return np.full_like(n, 4)
+
+# multiplicative cost of ctz skip-list files
+def ctz_cost(n, B):
+    return (np.ceil(n/B)*B) / n
+
+# combined multiplicative cost
+def file_cost(n, B):
+    return np.where(n < B/4, inline_cost(n, B), ctz_cost(n, B))
+
+t = np.arange(0.0, 80.0, 0.25)
+ax.plot(t, file_cost(t, 16))
+t1 = np.arange(0.0, 16.0/4.0 + 0.5, 0.25)
+t2 = np.arange(16.0/4.0, 80.0, 0.25)
+ax.plot(t1, ctz_cost(t1, 16), color='C0', linestyle=(2.65, (3.65,1.65)))
+ax.plot(t2, inline_cost(t2, 16), color='C0', linestyle=(3.65, (3.65,1.65)))
+
+ax.text(70.5, 4.15, 'inline file', size='small')
+ax.text(3.3, 5.85, 'ctz skip-list', rotation=-85, size='small')
+
+ax.set_xlabel('file size')
+ax.set_xlim(0, 80)
+ax.set_ylabel('multiplicative cost')
+ax.set_ylim(0, 6)
+
+xticks = np.arange(0, 80+1, 16)
+ax.set_xticks(xticks)
+ax.set_xticklabels(['%dKiB' % ((t*(4096/16))/1024) for t in xticks])
+yticks = np.arange(0, 6+1, 2)
+ax.set_yticks(yticks)
+ax.set_yticklabels(['%dx' % t for t in yticks])
+
+ax.spines['right'].set_visible(False)
+ax.spines['top'].set_visible(False)
+
+fig.tight_layout()
+plt.savefig('file-cost.svg', bbox_inches="tight")