1/*
2 * Copyright 2015 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef Stats_DEFINED
9#define Stats_DEFINED
10
11#include "SkString.h"
12#include "SkTSort.h"
13
14#ifdef SK_BUILD_FOR_WIN
15    static const char* kBars[] = { ".", "o", "O" };
16#else
17    static const char* kBars[] = { "▁", "▂", "▃", "▄", "▅", "▆", "▇", "█" };
18#endif
19
20struct Stats {
21    Stats(const SkTArray<double>& samples) {
22        int n = samples.count();
23        if (!n) {
24            min = max = mean = var = median = 0;
25            return;
26        }
27
28        min = samples[0];
29        max = samples[0];
30        for (int i = 0; i < n; i++) {
31            if (samples[i] < min) { min = samples[i]; }
32            if (samples[i] > max) { max = samples[i]; }
33        }
34
35        double sum = 0.0;
36        for (int i = 0 ; i < n; i++) {
37            sum += samples[i];
38        }
39        mean = sum / n;
40
41        double err = 0.0;
42        for (int i = 0 ; i < n; i++) {
43            err += (samples[i] - mean) * (samples[i] - mean);
44        }
45        var = err / (n-1);
46
47        SkAutoTMalloc<double> sorted(n);
48        memcpy(sorted.get(), samples.begin(), n * sizeof(double));
49        SkTQSort(sorted.get(), sorted.get() + n - 1);
50        median = sorted[n/2];
51
52        // Normalize samples to [min, max] in as many quanta as we have distinct bars to print.
53        for (int i = 0; i < n; i++) {
54            if (min == max) {
55                // All samples are the same value.  Don't divide by zero.
56                plot.append(kBars[0]);
57                continue;
58            }
59
60            double s = samples[i];
61            s -= min;
62            s /= (max - min);
63            s *= (SK_ARRAY_COUNT(kBars) - 1);
64            const size_t bar = (size_t)(s + 0.5);
65            SkASSERT_RELEASE(bar < SK_ARRAY_COUNT(kBars));
66            plot.append(kBars[bar]);
67        }
68    }
69
70    double min;
71    double max;
72    double mean;    // Estimate of population mean.
73    double var;     // Estimate of population variance.
74    double median;
75    SkString plot;  // A single-line bar chart (_not_ histogram) of the samples.
76};
77
78#endif//Stats_DEFINED
79