bench/FontCacheBench.cpp

/*
 * Copyright 2013 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "SkBenchmark.h"
#include "SkCanvas.h"
#include "SkFontHost.h"
#include "SkPaint.h"
#include "SkString.h"
#include "SkTemplates.h"

#include "gUniqueGlyphIDs.h"
#define gUniqueGlyphIDs_Sentinel    0xFFFF

static int count_glyphs(const uint16_t start[]) {
    const uint16_t* curr = start;
    while (*curr != gUniqueGlyphIDs_Sentinel) {
        curr += 1;
    }
    return static_cast<int>(curr - start);
}

class FontCacheBench : public SkBenchmark {
public:
    FontCacheBench()  {}

protected:
    virtual const char* onGetName() SK_OVERRIDE {
        return "fontcache";
    }

    virtual void onDraw(const int loops, SkCanvas* canvas) SK_OVERRIDE {
        SkPaint paint;
        this->setupPaint(&paint);
        paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);

        const uint16_t* array = gUniqueGlyphIDs;
        while (*array != gUniqueGlyphIDs_Sentinel) {
            int count = count_glyphs(array);
            for (int i = 0; i < loops; ++i) {
                paint.measureText(array, count * sizeof(uint16_t));
            }
            array += count + 1;    // skip the sentinel
        }
    }

private:
    typedef SkBenchmark INHERITED;
};

///////////////////////////////////////////////////////////////////////////////

static uint32_t rotr(uint32_t value, unsigned bits) {
    return (value >> bits) | (value << (32 - bits));
}

typedef uint32_t (*HasherProc)(uint32_t);

static uint32_t hasher0(uint32_t value) {
    value = value ^ (value >> 16);
    return value ^ (value >> 8);
}

static uint32_t hasher2(uint32_t h) {
    h ^= h >> 16;
    h *= 0x85ebca6b;
    h ^= h >> 13;
    h *= 0xc2b2ae35;
    h ^= h >> 16;

    h ^= (h >> 8);
    return h;
}

static const struct {
    const char* fName;
    HasherProc  fHasher;
} gRec[] = {
    { "hasher0",  hasher0 },
    { "hasher2",  hasher2 },
};

#define kMaxHashBits   12
#define kMaxHashCount  (1 << kMaxHashBits)

static int count_collisions(const uint16_t array[], int count, HasherProc proc,
                            unsigned hashMask) {
    char table[kMaxHashCount];
    sk_bzero(table, sizeof(table));

    int collisions = 0;
    for (int i = 0; i < count; ++i) {
        int index = proc(array[i]) & hashMask;
        collisions += table[index];
        table[index] = 1;
    }
    return collisions;
}

static void dump_array(const uint16_t array[], int count) {
    for (int i = 0; i < count; ++i) {
        SkDebugf(" %d,", array[i]);
    }
    SkDebugf("\n");
}

class FontCacheEfficiency : public SkBenchmark {
public:
    FontCacheEfficiency()  {
        if (false) dump_array(NULL, 0);
        if (false) rotr(0, 0);
    }

protected:
    virtual const char* onGetName() SK_OVERRIDE {
        return "fontefficiency";
    }

    virtual void onDraw(const int loops, SkCanvas* canvas) SK_OVERRIDE {
        static bool gDone;
        if (gDone) {
            return;
        }
        gDone = true;

        for (int hashBits = 6; hashBits <= 12; hashBits += 1) {
            int hashMask = ((1 << hashBits) - 1);
            for (int limit = 32; limit <= 1024; limit <<= 1) {
                for (size_t i = 0; i < SK_ARRAY_COUNT(gRec); ++i) {
                    int collisions = 0;
                    int glyphs = 0;
                    const uint16_t* array = gUniqueGlyphIDs;
                    while (*array != gUniqueGlyphIDs_Sentinel) {
                        int count = SkMin32(count_glyphs(array), limit);
                        collisions += count_collisions(array, count, gRec[i].fHasher, hashMask);
                        glyphs += count;
                        array += count + 1;    // skip the sentinel
                    }
                    SkDebugf("hashBits [%d] limit [%d] collisions [%d / %d = %1.2g%%] using %s\n", hashBits, limit, collisions, glyphs,
                             collisions * 100.0 / glyphs, gRec[i].fName);
                }
            }
        }
    }

private:
    typedef SkBenchmark INHERITED;
};

///////////////////////////////////////////////////////////////////////////////

DEF_BENCH( return new FontCacheBench(); )

// undefine this to run the efficiency test
//DEF_BENCH( return new FontCacheEfficiency(); )