other implementation

examples_ptx/radixSort/radixSort1.ispc

@@ -0,0 +1,73 @@
+#define NUMBITS 8
+#define NUMBUCKETS (1<<NUMBITS)
+task
+void localHistogram(
+    uniform unsigned int32 keys_all[],
+    uniform          int32 bit,
+    uniform          int32 count_all,
+    uniform          int32 counts_all[])
+{
+  const uniform unsigned int mask = (1 << NUMBITS) - 1;
+  for (uniform int block = taskIndex; block < numBlocks; block += taskCount)
+  {
+    uniform unsigned int32 * uniform keys =   keys_all + block*blockSize;
+    uniform          int32 * uniform keys = counts_all + block*NUMBUCKETS;
+    uniform          int32 count = min(count_all - block*blockSize, blockSize);
+
+    foreach (i = 0 ... NUMBUCKETS)
+      counts[i] = 0;
+
+    foreach (i = 0 ... count)
+    {
+      const int key = mask & (keys[i] >> bit);
+      atomic_add_local(&counts[key], 1);
+    }
+  }
+}
+
+task
+void globalHistogram(
+    uniform int32 counts_all[],
+    uniform int32 countsGlobal[])
+{
+  uniform int32 (* uniform countsBlock)[NUMBUCKETS] = (uniform int (*)[NUMBUCKETS]) counts;
+  for (uniform int digit = taskIndex; digit < NUMBUCKETS; digit += taskCount)
+  {
+    int sum = 0;
+    foreach (block = 0...numBlocks)
+      sum += counts[block][digit];
+    countsGlobal[digit] = reduce_add(sum);
+  }
+}
+
+export void radixSort()
+{
+  for (uniform int bit = 0; bit < 32; bit += NUMBITS)
+  {
+    /* histogramming each of the block */
+    launch [nBlocks] localHistogram(keys, bit, count, counts);
+    sync;
+
+    /* compute global histogram */
+    launch [nBlocks] globalHistogram(counts, countsGlobal);
+    sync();
+
+    /* exclusive scan on global histogram */
+    int carry = 0;
+    foreach (i = 0...NUMBUCKETS)
+    {
+      const int value = countsGlobal[i];
+      const int scan  = exclusive_scan(value);
+      scanGlobal[i] = value + carry;
+      carry = broadcast(scan+value, programCount-1);
+    }
+          
+    /* computing offsets for each digit */
+    launch [nBlocks] computeGlobalOffset();
+    sync();
+
+    /* sorting */
+    launch [nBlocks] sort()
+
+  }
+}