Do not calculate many sierpinski fractals for each nanobench run unless needed

bench/PictureNestingBench.cpp

Index: bench/PictureNestingBench.cpp
diff --git a/bench/PictureNestingBench.cpp b/bench/PictureNestingBench.cpp
index c2848833b747a8d8afaaf09117addeb75129fe04..224f7355f90541f07efb48353e467ef488d51897 100644
--- a/bench/PictureNestingBench.cpp
+++ b/bench/PictureNestingBench.cpp
@@ -14,20 +14,23 @@
 #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());
+    }
 
+protected:
+    virtual void onPreDraw() SK_OVERRIDE {

[mtklein, 2014/11/13 16:15:04]

Moving this part to onPreDraw() might be overkill.  Those fPaint.set* methods
are trivially cheap.

[Kimmo Kinnunen, 2014/11/18 12:42:19]

Done.

         fPaint.setColor(SK_ColorRED);
         fPaint.setAntiAlias(true);
         fPaint.setStyle(SkPaint::kStroke_Style);
-        SkAutoTUnref<SkCanvas> nullCanvas(SkCreateNullCanvas());
-        fName.printf("picture_nesting_%s_%d", name, this->sierpinsky(nullCanvas, 0, fPaint));
     }
 
-protected:
     virtual const char* onGetName() SK_OVERRIDE {
         return fName.c_str();
     }
@@ -37,7 +40,8 @@ protected:
         canvas->save();
         canvas->scale(SkIntToScalar(canvasSize.x()), SkIntToScalar(canvasSize.y()));
 
-        this->sierpinsky(canvas, 0, fPaint);
+        SkDEBUGCODE(int pics = ) this->sierpinsky(canvas, 0, fPaint);
+        SkASSERT(pics == this->countPics());
 
         canvas->restore();
     }
@@ -86,6 +90,15 @@ protected:
     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 (pow(3, fMaxPictureLevel) - 1) / 2;

[mtklein, 2014/11/13 16:15:04]

You may need some explicit casts in here.  Our compilers are a little anal about
warning you when you might lose precision.

[Kimmo Kinnunen, 2014/11/18 12:42:19]

Done.

+    }
+
     SkString fName;
     SkPaint  fPaint;
 
@@ -123,6 +136,10 @@ class PictureNestingPlayback : public PictureNesting {
 public:
     PictureNestingPlayback(int maxLevel, int maxPictureLevel)
         : INHERITED("playback", maxLevel, maxPictureLevel) {
+    }
+protected:
+    virtual void onPreDraw() SK_OVERRIDE {
+        this->INHERITED::onPreDraw();
 
         SkIPoint canvasSize = onGetSize();
         SkPictureRecorder recorder;
@@ -133,7 +150,6 @@ public:
         fPicture.reset(recorder.endRecording());
     }
 
-protected:
     virtual void onDraw(const int loops, SkCanvas* canvas) {
         for (int i = 0; i < loops; i++) {
             canvas->drawPicture(fPicture);