PictureNestingBench: stay in ints.

bench/PictureNestingBench.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Benchmark.h"
 #include "SkCanvas.h"
 #include "SkColor.h"
 #include "SkNullCanvas.h"
 #include "SkPaint.h"
 #include "SkPicture.h"
 #include "SkPictureRecorder.h"
 #include "SkString.h"
 
-#include <math.h>
-
 class PictureNesting : public Benchmark {
 public:
     PictureNesting(const char* name, int maxLevel, int maxPictureLevel)
         : fMaxLevel(maxLevel)
         , fMaxPictureLevel(maxPictureLevel) {
         fName.printf("picture_nesting_%s_%d", name, this->countPics());
         fPaint.setColor(SK_ColorRED);
         fPaint.setAntiAlias(true);
         fPaint.setStyle(SkPaint::kStroke_Style);
     }
@@ skipping 57 matching lines @@
     int fMaxLevel;
     int fMaxPictureLevel;
 
 private:
     int countPics() const {
         // Solve: pics from sierpinsky
         // f(m) = 1 + 3*f(m - 1)
         // f(0) = 0
         //   via "recursive function to closed form" tricks
         // f(m) = 1/2 (3^m - 1)
-        return static_cast<int>((pow(3.0, fMaxPictureLevel) - 1.0) / 2.0);
+        int pics = 1;
+        for (int i = 0; i < fMaxPictureLevel; i++) {
+            pics *= 3;
+        }
+        pics--;
+        pics /= 2;
+        return pics;
     }
 
     SkString fName;
     SkPaint  fPaint;
 
     typedef Benchmark INHERITED;
 };
 
 class PictureNestingRecording : public PictureNesting {
 public:
@@ skipping 64 matching lines @@
 
 DEF_BENCH( return new PictureNestingPlayback(8, 0); )
 DEF_BENCH( return new PictureNestingPlayback(8, 1); )
 DEF_BENCH( return new PictureNestingPlayback(8, 2); )
 DEF_BENCH( return new PictureNestingPlayback(8, 3); )
 DEF_BENCH( return new PictureNestingPlayback(8, 4); )
 DEF_BENCH( return new PictureNestingPlayback(8, 5); )
 DEF_BENCH( return new PictureNestingPlayback(8, 6); )
 DEF_BENCH( return new PictureNestingPlayback(8, 7); )
 DEF_BENCH( return new PictureNestingPlayback(8, 8); )