Benchmark::OnRun: clarify, simplify, avoid possible divide by 0

src/Benchmark.cpp

@@ -354,12 +354,12 @@ void BenchmarkDialog::OnRun( wxCommandEvent & WXUNUSED(event))
 
    srand(randSeed);
 
-   int nChunks, chunkSize;
+   size_t nChunks, chunkSize;
    //chunkSize = 7500 + (rand() % 1000);
    chunkSize = 200 + (rand() % 100);
    nChunks = (dataSize * 1048576) / (chunkSize*sizeof(short));
-   while(nChunks < 20 || chunkSize > (blockSize*1024)/4) {
+   while(nChunks < 20 || chunkSize > ((unsigned long)(blockSize)*1024)/4) {
-      chunkSize = (chunkSize / 2) + (rand() % 100);
+      chunkSize = std::max( size_t(1), (chunkSize / 2) + (rand() % 100) );
       nChunks = (dataSize * 1048576) / (chunkSize*sizeof(short));
    }
 
@@ -374,7 +374,6 @@ void BenchmarkDialog::OnRun( wxCommandEvent & WXUNUSED(event))
    int trials = numEdits;
 
    short *small1 = new short[nChunks];
-   short *small2 = new short[nChunks];
    short *block = new short[chunkSize];
 
    Printf(wxT("Preparing...\n"));
@@ -416,8 +415,13 @@ void BenchmarkDialog::OnRun( wxCommandEvent & WXUNUSED(event))
 
    timer.Start();
    for (z = 0; z < trials; z++) {
-      int x0 = rand() % nChunks;
+      // First chunk to cut
-      int xlen = 1 + (rand() % (nChunks - x0));
+      // 0 <= x0 < nChunks
+      const size_t x0 = rand() % nChunks;
+
+      // Number of chunks to cut
+      // 1 <= xlen <= nChunks - x0
+      const size_t xlen = 1 + (rand() % (nChunks - x0));
       if (mEditDetail)
          Printf(wxT("Cut: %d - %d \n"), x0 * chunkSize, (x0 + xlen) * chunkSize);
 
@@ -431,7 +435,10 @@ void BenchmarkDialog::OnRun( wxCommandEvent & WXUNUSED(event))
          goto fail;
       }
 
-      int y0 = rand() % (nChunks - xlen);
+      // Position to paste
+      // 0 <= y0 <= nChunks - xlen
+      const size_t y0 = rand() % (nChunks - xlen + 1);
+
       if (mEditDetail)
          Printf(wxT("Paste: %d\n"), y0 * chunkSize);
 
@@ -447,18 +454,12 @@ void BenchmarkDialog::OnRun( wxCommandEvent & WXUNUSED(event))
                 t->GetClipByIndex(0)->GetSequence()->GetNumSamples().as_long_long());
          goto fail;
       }
-      // Copy
+
-      for (i = 0; i < xlen; i++)
+      // Permute small1 correspondingly to the cut and paste
-         small2[i] = small1[x0 + i];
+      auto first = &small1[0];
-      // Delete
+      if (x0 + xlen < nChunks)
-      for (i = 0; i < (nChunks - x0 - xlen); i++)
+         std::rotate( first + x0, first + x0 + xlen, first + nChunks );
-         small1[x0 + i] = small1[x0 + xlen + i];
+      std::rotate( first + y0, first + nChunks - xlen, first + nChunks );
-      // Insert
-      for (i = 0; i < (nChunks - xlen - y0); i++)
-         small1[nChunks - i - 1] = small1[nChunks - i - 1 - xlen];
-      // Paste
-      for (i = 0; i < xlen; i++)
-         small1[y0 + i] = small2[i];
    }
 
    elapsed = timer.Time();
@@ -534,7 +535,6 @@ void BenchmarkDialog::OnRun( wxCommandEvent & WXUNUSED(event))
 
  success:
    delete[]small1;
-   delete[]small2;
    delete[]block;
 
    dd.reset();