HE3: RC3 - V2 code refactor version measurements

homework_3/src/bitonicsort.hpp

@@ -112,8 +112,8 @@ template <typename ValueT>
 __device__ void exchange(ValueT* data, threadId_t tid, threadId_t partner, bool keepSmall) {
     if (( keepSmall && (data[tid] > data[partner])) ||
         (!keepSmall && (data[tid] < data[partner])) ) {
-        ValueT temp = data[tid];
-        data[tid] = data[partner];
+        ValueT temp   = data[tid];
+        data[tid]     = data[partner];
         data[partner] = temp;
     }
 }
@@ -378,6 +378,7 @@ __global__ void interBlockStep(ValueT* data, size_t n, size_t step, size_t stage
     }
 }
 
+
 /*!
  * This is unrolled part of the bitonic double loop.
  *
@@ -399,42 +400,44 @@ __global__ void inBlockStep(ValueT* data, size_t n, size_t innerSteps, size_t st
      * Here we skip blocks every time (one for SizeToThreadsRatio = 2)
      * And we cache the neighbor block address indexes in local (shared) memory
      */
-    threadId_t gIdx0 = threadIdx.x + SizeToThreadsRatio * blockIdx.x * blockDim.x;
-    threadId_t lIdx0 = toLocal(gIdx0, blockDim.x);
+    threadId_t gIdx = threadIdx.x + SizeToThreadsRatio * blockIdx.x * blockDim.x;
+    threadId_t lIdx = toLocal(gIdx, blockDim.x);
 
-    if (gIdx0 + blockDim.x >= n)   // Boundary check
+    if (gIdx + blockDim.x >= n)   // Boundary check
         return;
 
     // Fetch to local memory the entire effective block size (2 positions for each thread)
-    shared_data[lIdx0]              = data[gIdx0];
-    shared_data[lIdx0 + blockDim.x] = data[gIdx0 + blockDim.x];
+    shared_data[lIdx]              = data[gIdx];
+    shared_data[lIdx + blockDim.x] = data[gIdx + blockDim.x];
     __syncthreads();
 
     for (size_t step = innerSteps + 1; step > 0; ) {
         --step;
 
-        // Init thread global and local indices
-        threadId_t gIdx = gIdx0;
-        threadId_t lIdx = lIdx0;
         // Find partner and keep-small configuration based on the global data positions
         threadId_t pIdx  = partner(gIdx, step);
         if (gIdx > pIdx) {
-            // Shift inside effective block
-            gIdx += blockDim.x; // global
-            pIdx += blockDim.x;
-            lIdx += blockDim.x;	// local
-        }
-        bool keep = keepSmall(gIdx, pIdx, stage);
+            // Work on the right site
+            bool keep = keepSmall(gIdx + blockDim.x, pIdx + blockDim.x, stage);
 
-        // Exchange data on local(shared) copy
-        threadId_t lpIdx = toLocal(pIdx, blockDim.x);
-        exchange(shared_data, lIdx, lpIdx, keep);
+            // Exchange data on local(shared) copy
+            threadId_t lpIdx  = toLocal(pIdx + blockDim.x, blockDim.x);
+            exchange(shared_data, lIdx + blockDim.x, lpIdx, keep);
+        }
+        else {
+            // Work on the left site
+            bool keep = keepSmall(gIdx, pIdx, stage);
+
+            // Exchange data on local(shared) copy
+            threadId_t lpIdx  = toLocal(pIdx, blockDim.x);
+            exchange(shared_data, lIdx, lpIdx, keep);
+        }
         __syncthreads();
     }
 
     // Write back to global memory (no sync here, there will be sync from host)
-    data[gIdx0]              = shared_data[lIdx0];
-    data[gIdx0 + blockDim.x] = shared_data[lIdx0 + blockDim.x];
+    data[gIdx]              = shared_data[lIdx];
+    data[gIdx + blockDim.x] = shared_data[lIdx + blockDim.x];
 }
 
 /*!
@@ -459,6 +462,59 @@ __global__ void prephase(ValueT* data, size_t n, size_t stages, size_t maxStages
      * Here we skip blocks every time (one for SizeToThreadsRatio = 2)
      * And we cache the neighbor block address indexes in local (shared) memory
      */
+    threadId_t gIdx = threadIdx.x + SizeToThreadsRatio * blockIdx.x * blockDim.x;
+    threadId_t lIdx = toLocal(gIdx, blockDim.x);
+
+    if (gIdx + blockDim.x >= n)   // Boundary check
+        return;
+
+    // Fetch to local memory the entire effective block size (2 positions for each thread)
+    shared_data[lIdx]              = data[gIdx];
+    shared_data[lIdx + blockDim.x] = data[gIdx + blockDim.x];
+    __syncthreads();
+
+    for (size_t stage = 1; (stage <= stages) && (stage <= maxStages); ++stage) {
+        for (size_t step = stage; step > 0; ) {
+            --step;
+
+            // Find partner and keep-small configuration based on the global data positions
+            threadId_t pIdx  = partner(gIdx, step);
+            if (gIdx > pIdx) {
+                // Work on the right site
+                bool keep = keepSmall(gIdx + blockDim.x, pIdx + blockDim.x, stage);
+
+                // Exchange data on local(shared) copy
+                threadId_t lpIdx  = toLocal(pIdx + blockDim.x, blockDim.x);
+                exchange(shared_data, lIdx + blockDim.x, lpIdx, keep);
+            }
+            else {
+                // Work on the left site
+                bool keep = keepSmall(gIdx, pIdx, stage);
+
+                // Exchange data on local(shared) copy
+                threadId_t lpIdx  = toLocal(pIdx, blockDim.x);
+                exchange(shared_data, lIdx, lpIdx, keep);
+            }
+            __syncthreads();
+        }
+    }
+
+    // Write back to global memory (no sync here, there will be sync from host)
+    data[gIdx]              = shared_data[lIdx];
+    data[gIdx + blockDim.x] = shared_data[lIdx + blockDim.x];
+
+#if 0
+    /*
+     * Idea:
+     * - Keep a register copy of data[gIdx0], and data[gIdx0 + blockDim.x]
+     * - Instead of exchange in shared_data, read in register the partner and exchange there.
+     * - Write back only if there was an exchange
+     *
+     * ^^
+     * Unfortunately this breaks sequential consistency and register values (lValve) does not match with share_data
+     * or even lValueR0 and lValueL0. Maybe there is something to do with register spilling (lValue keeps spill
+     * on local mem).
+     */
     threadId_t gIdx0 = threadIdx.x + SizeToThreadsRatio * blockIdx.x * blockDim.x;
     threadId_t lIdx0 = toLocal(gIdx0, blockDim.x);
 
@@ -466,29 +522,40 @@ __global__ void prephase(ValueT* data, size_t n, size_t stages, size_t maxStages
         return;
 
     // Fetch to local memory the entire effective block size (2 positions for each thread)
-    shared_data[lIdx0]              = data[gIdx0];
-    shared_data[lIdx0 + blockDim.x] = data[gIdx0 + blockDim.x];
+    // also keep thread's init values (L and R) on register locations
+    ValueT lValueL0                 = data[gIdx0];
+    ValueT lValueR0                 = data[gIdx0 + blockDim.x];
+    shared_data[lIdx0]              = lValueL0;
+    shared_data[lIdx0 + blockDim.x] = lValueR0;
     __syncthreads();
+
     for (size_t stage = 1; (stage <= stages) && (stage <= maxStages); ++stage) {
         for (size_t step = stage; step > 0; ) {
             --step;
 
-            // Init thread global and local indices
+            // Init thread global, local indices and active local register value
             threadId_t gIdx = gIdx0;
             threadId_t lIdx = lIdx0;
+            ValueT lValue   = lValueL0; // "Me" on the left side of effective block
+
             // Find partner and keep-small configuration based on the global data positions
             threadId_t pIdx  = partner(gIdx, step);
             if (gIdx > pIdx) {
                 // Shift inside effective block
-                gIdx += blockDim.x; // global
+                gIdx += blockDim.x;  // global
                 pIdx += blockDim.x;
-                lIdx += blockDim.x;	// local
+                lIdx += blockDim.x;  // local
+                lValue = lValueR0;   // The other me (the right side)
             }
             bool keep = keepSmall(gIdx, pIdx, stage);
 
             // Exchange data on local(shared) copy
             threadId_t lpIdx = toLocal(pIdx, blockDim.x);
-            exchange(shared_data, lIdx, lpIdx, keep);
+            ValueT pValue = shared_data[lpIdx];
+            if (exchangeVals(&lValue, &pValue, keep)) {
+                shared_data[lIdx]  = lValue;
+                shared_data[lpIdx] = pValue;
+            }
             __syncthreads();
         }
     }
@@ -496,8 +563,10 @@ __global__ void prephase(ValueT* data, size_t n, size_t stages, size_t maxStages
     // Write back to global memory (no sync here, there will be sync from host)
     data[gIdx0]              = shared_data[lIdx0];
     data[gIdx0 + blockDim.x] = shared_data[lIdx0 + blockDim.x];
+#endif
 }
 
+
 /*!
  * A CUDA version of the Bitonic sort algorithm.
  *

homework_3/src/config.h

@@ -16,8 +16,10 @@
 /*
  * Versioning:
  * - RC1: First version to test on HPC
+ * - RC2: A pre-phase added for v1 and v2
+ * - RC3:
  */
-static constexpr char version[] = "0.1";
+static constexpr char version[] = "0.2";
 
 /*
  * Defines for different version of the exercise