diff --git a/examples_ptx/mergeSort/mergeSort.cu b/examples_ptx/mergeSort/mergeSort.cu
index 39032279..b694e7b4 100644
--- a/examples_ptx/mergeSort/mergeSort.cu
+++ b/examples_ptx/mergeSort/mergeSort.cu
@@ -233,7 +233,7 @@ void mergeSortGang(
     uniform Val_t srcVal[],
     uniform int batchSize)
 {
-  uniform int nTasks = batchSize/4;
+  uniform int nTasks = batchSize;
   launch (nTasks,1,1,mergeSortGangKernel)(batchSize, dstKey, dstVal, srcKey, srcVal);
   sync;
 }
@@ -306,7 +306,7 @@ void generateSampleRanks(
     (N - lastSegmentElements) / (2 * SAMPLE_STRIDE);
 
   uniform int nBlocks = iDivUp(threadCount, SAMPLE_STRIDE);
-  uniform int nTasks = nBlocks/4;
+  uniform int nTasks = nBlocks;
 
   launch (nTasks,1,1, generateSampleRanksKernel)(nBlocks, ranksA, ranksB, srcKey, stride, N, threadCount);
   sync;
@@ -372,7 +372,7 @@ void mergeRanksAndIndices(
     (N - lastSegmentElements) / (2 * SAMPLE_STRIDE);
 
   const uniform int nBlocks = iDivUp(threadCount, SAMPLE_STRIDE);
-  uniform int nTasks = nBlocks/4;
+  uniform int nTasks = nBlocks;
 
   launch (nTasks,1,1,mergeRanksAndIndicesKernel)(
       nBlocks,
@@ -448,20 +448,21 @@ void mergeElementaryIntervalsKernel(
     }
 
     // Compute destination addresses for merge data
-    int dstPosA = binarySearchExclusive1(keyA, keyB, lenSrcB, SAMPLE_STRIDE) + programIndex;
-    int dstPosB = binarySearchInclusive1(keyB, keyA, lenSrcA, SAMPLE_STRIDE) + programIndex;
+    int dstPosA, dstPosB, dstA = -1, dstB = -1;
+    if (any(programIndex < lenSrcA))
+      dstPosA = binarySearchExclusive1(keyA, keyB, lenSrcB, SAMPLE_STRIDE) + programIndex;
+    if (any(programIndex < lenSrcB))
+      dstPosB = binarySearchInclusive1(keyB, keyA, lenSrcA, SAMPLE_STRIDE) + programIndex;
 
-
-    int dstA = -1, dstB = -1;
     if (programIndex < lenSrcA && dstPosA < lenSrcA)
       dstA = segmentBase + startDstA + dstPosA;
-    if (programIndex < lenSrcB && dstPosB < lenSrcA)
-      dstB = segmentBase + startDstA + dstPosB;
-
     dstPosA -= lenSrcA;
-    dstPosB -= lenSrcA;
     if (programIndex < lenSrcA && dstPosA < lenSrcB)
       dstA = segmentBase + startDstB + dstPosA;
+
+    if (programIndex < lenSrcB && dstPosB < lenSrcA)
+      dstB = segmentBase + startDstA + dstPosB;
+    dstPosB -= lenSrcA;
     if (programIndex < lenSrcB && dstPosB < lenSrcB)
       dstB = segmentBase + startDstB + dstPosB;
 
@@ -499,7 +500,7 @@ void mergeElementaryIntervals(
   const uniform int mergePairs = (lastSegmentElements > stride) ? getSampleCount(N) : (N - lastSegmentElements) / SAMPLE_STRIDE;
 
 
-  nTasks = mergePairs/(4*programCount);
+  nTasks = mergePairs/(programCount);
 
   launch (nTasks,1,1, mergeElementaryIntervalsKernel)(
       mergePairs,
diff --git a/examples_ptx/mergeSort/mergeSort.ispc b/examples_ptx/mergeSort/mergeSort.ispc
index 04510c3d..cdbd27b4 100644
--- a/examples_ptx/mergeSort/mergeSort.ispc
+++ b/examples_ptx/mergeSort/mergeSort.ispc
@@ -221,7 +221,7 @@ void mergeSortGang(
 {
   uniform int nTasks = num_cores()*4;
 #ifdef __NVPTX__
-  nTasks = iDivUp(batchSize,4);
+  nTasks = iDivUp(batchSize,1);
 #endif
   launch [nTasks] mergeSortGangKernel(batchSize, dstKey, dstVal, srcKey, srcVal, 2*programCount);
   sync;
@@ -297,7 +297,7 @@ void generateSampleRanks(
   uniform int nBlocks = iDivUp(threadCount, SAMPLE_STRIDE);
   uniform int nTasks = num_cores()*4;
 #ifdef __NVPTX__
-  nTasks = iDivUp(nBlocks,4);
+  nTasks = iDivUp(nBlocks,1);
 #endif
 
   launch [nTasks] generateSampleRanksKernel(nBlocks, ranksA, ranksB, srcKey, stride, N, threadCount);
@@ -367,7 +367,7 @@ void mergeRanksAndIndices(
   uniform int nTasks = num_cores()*4;
 
 #ifdef __NVPTX__
-  nTasks = iDivUp(nBlocks,4);
+  nTasks = iDivUp(nBlocks,1);
 #endif
 
   launch [nTasks] mergeRanksAndIndicesKernel(
@@ -492,7 +492,7 @@ void mergeElementaryIntervals(
 
   uniform int nTasks = num_cores()*4;
 #ifdef __NVPTX__
-  nTasks = iDivUp(mergePairs,4*programCount);
+  nTasks = iDivUp(mergePairs,1*programCount);
 #endif
 
   launch [nTasks] mergeElementaryIntervalsKernel(