From 75fe8235f78520fbbfff7c9c035ecd9f1aa3e6f6 Mon Sep 17 00:00:00 2001
From: Cedric Nugteren <web@cedricnugteren.nl>
Date: Sat, 23 Jul 2016 10:20:11 +0200
Subject: Improved the XgemvFastRot kernel by tiled loading of the input matrix
 A, enabling better memory performance

---
 src/database/kernels/xgemv.hpp       |   2 +-
 src/kernels/level2/xgemv_fast.opencl | 137 +++++++++++++++++------------------
 src/routines/level2/xgemv.cpp        |   2 +-
 src/tuning/kernels/xgemv.cpp         |  20 +++--
 4 files changed, 85 insertions(+), 76 deletions(-)

diff --git a/src/database/kernels/xgemv.hpp b/src/database/kernels/xgemv.hpp
index 65f4b5c8..6fb68858 100644
--- a/src/database/kernels/xgemv.hpp
+++ b/src/database/kernels/xgemv.hpp
@@ -36,7 +36,7 @@ const Database::DatabaseEntry Database::XgemvSingle = {
   "Xgemv", Precision::kSingle, {
     { // AMD GPUs
       kDeviceTypeGPU, "AMD", {
-        { "AMD Radeon R9 M370X Compute Engine",              { {"WGS1",128}, {"WPT1",1}, {"VW2",1}, {"WGS2",128}, {"WPT2",1}, {"VW3",1}, {"WGS3",64}, {"WPT3",1} } },
+        { "AMD Radeon R9 M370X Compute Engine",              { {"WGS1",128}, {"WPT1",1}, {"VW2",1}, {"WGS2",128}, {"WPT2",1}, {"VW3",4}, {"WGS3",32}, {"WPT3",32} } },
         { "Hawaii",                                          { {"WGS1",128}, {"WPT1",1}, {"VW2",1}, {"WGS2",64}, {"WPT2",1}, {"VW3",1}, {"WGS3",64}, {"WPT3",1} } },
         { "Oland",                                           { {"WGS1",128}, {"WPT1",1}, {"VW2",1}, {"WGS2",64}, {"WPT2",1}, {"VW3",4}, {"WGS3",256}, {"WPT3",4} } },
         { "Pitcairn",                                        { {"WGS1",256}, {"WPT1",1}, {"VW2",1}, {"WGS2",64}, {"WPT2",1}, {"VW3",1}, {"WGS3",64}, {"WPT3",1} } },
diff --git a/src/kernels/level2/xgemv_fast.opencl b/src/kernels/level2/xgemv_fast.opencl
index 1127a0b6..1d34de96 100644
--- a/src/kernels/level2/xgemv_fast.opencl
+++ b/src/kernels/level2/xgemv_fast.opencl
@@ -38,7 +38,7 @@ R"(
   #define WGS3 64     // The local work-group size
 #endif
 #ifndef WPT3
-  #define WPT3 1      // The amount of work-per-thread
+  #define WPT3 1      // The tile-size
 #endif
 #ifndef VW3
   #define VW3 1       // Vector width of matrix A loads
@@ -74,18 +74,12 @@ R"(
 
 // =================================================================================================
 
-// Loads a vector input value (1/2)
+// Loads a vector input value
 inline realVF LoadMatrixAVF(const __global realVF* restrict agm, const int x, const int y,
                             const int a_ld) {
   return agm[a_ld*y + x];
 }
 
-// Loads a vector input value (2/2): as before, but different data-type
-inline realVFR LoadMatrixAVFR(const __global realVFR* restrict agm, const int x, const int y,
-                              const int a_ld) {
-  return agm[a_ld*y + x];
-}
-
 // =================================================================================================
 
 // Faster version of the kernel, assuming that:
@@ -110,7 +104,7 @@ __kernel void XgemvFast(const int m, const int n,
   // Local memory for the vector X
   __local real xlm[WGS2];
 
-  // Initializes the accumulation register
+  // Initializes the accumulation registers
   real acc[WPT2];
   #pragma unroll
   for (int w=0; w<WPT2; ++w) {
@@ -134,7 +128,7 @@ __kernel void XgemvFast(const int m, const int n,
       #pragma unroll
       for (int w=0; w<WPT2/VW2; ++w) {
         const int gid = (WPT2/VW2)*get_global_id(0) + w;
-        realVF avec = LoadMatrixAVF(agm, gid, k, a_ld/VW2);
+        realVF avec = agm[(a_ld/VW2)*k + gid];
         #if VW2 == 1
           MultiplyAdd(acc[VW2*w+0], xlm[kl], avec);
         #elif VW2 == 2
@@ -209,72 +203,80 @@ __kernel void XgemvFastRot(const int m, const int n,
   const real alpha = GetRealArg(arg_alpha);
   const real beta = GetRealArg(arg_beta);
 
+  // Local memory to store a tile of the matrix (for coalescing)
+  __local real tile[WGS3 * WPT3];
+  const int lid = get_local_id(0);
+  const int lid_mod = lid % WPT3;
+  const int lid_div = lid / WPT3;
+
   // Local memory for the vector X
-  __local real xlm[WGS3];
+  __local real xlm[WPT3];
 
   // Initializes the accumulation register
-  real acc[WPT3];
-  #pragma unroll
-  for (int w=0; w<WPT3; ++w) {
-    SetToZero(acc[w]);
-  }
+  real acc;
+  SetToZero(acc);
 
   // Loops over work-group sized portions of the work
-  for (int kwg=0; kwg<n; kwg+=WGS3) {
+  for (int kwg=0; kwg<n; kwg+=WPT3) {
 
     // Loads the vector X into local memory
-    const int lid = get_local_id(0);
-    xlm[lid] = xgm[(kwg + lid)*x_inc + x_offset];
+    xlm[lid] = xgm[(kwg + lid) * x_inc + x_offset];
+
+    // Loads the matrix A into local memory
+    #pragma unroll
+    for (int kl=0; kl<WPT3/VW3; ++kl) {
+      const int x = (kwg/VW3) + kl;
+      const int y = get_group_id(0) * WGS3 + lid;
+      realVFR avec = agm[(a_ld/VW3) * y + x];
+      #if VW3 == 1
+        tile[(kl*VW3 + 0) * WGS3 + lid] = avec;
+      #elif VW3 == 2
+        tile[(kl*VW3 + 0) * WGS3 + lid] = avec.x;
+        tile[(kl*VW3 + 1) * WGS3 + lid] = avec.y;
+      #elif VW3 == 4
+        tile[(kl*VW3 + 0) * WGS3 + lid] = avec.x;
+        tile[(kl*VW3 + 1) * WGS3 + lid] = avec.y;
+        tile[(kl*VW3 + 2) * WGS3 + lid] = avec.z;
+        tile[(kl*VW3 + 3) * WGS3 + lid] = avec.w;
+      #elif VW3 == 8
+        tile[(kl*VW3 + 0) * WGS3 + lid] = avec.s0;
+        tile[(kl*VW3 + 1) * WGS3 + lid] = avec.s1;
+        tile[(kl*VW3 + 2) * WGS3 + lid] = avec.s2;
+        tile[(kl*VW3 + 3) * WGS3 + lid] = avec.s3;
+        tile[(kl*VW3 + 4) * WGS3 + lid] = avec.s4;
+        tile[(kl*VW3 + 5) * WGS3 + lid] = avec.s5;
+        tile[(kl*VW3 + 6) * WGS3 + lid] = avec.s6;
+        tile[(kl*VW3 + 7) * WGS3 + lid] = avec.s7;
+      #elif VW3 == 16
+        tile[(kl*VW3 + 0) * WGS3 + lid] = avec.s0;
+        tile[(kl*VW3 + 1) * WGS3 + lid] = avec.s1;
+        tile[(kl*VW3 + 2) * WGS3 + lid] = avec.s2;
+        tile[(kl*VW3 + 3) * WGS3 + lid] = avec.s3;
+        tile[(kl*VW3 + 4) * WGS3 + lid] = avec.s4;
+        tile[(kl*VW3 + 5) * WGS3 + lid] = avec.s5;
+        tile[(kl*VW3 + 6) * WGS3 + lid] = avec.s6;
+        tile[(kl*VW3 + 7) * WGS3 + lid] = avec.s7;
+        tile[(kl*VW3 + 8) * WGS3 + lid] = avec.s8;
+        tile[(kl*VW3 + 9) * WGS3 + lid] = avec.s9;
+        tile[(kl*VW3 + 10) * WGS3 + lid] = avec.sA;
+        tile[(kl*VW3 + 11) * WGS3 + lid] = avec.sB;
+        tile[(kl*VW3 + 12) * WGS3 + lid] = avec.sC;
+        tile[(kl*VW3 + 13) * WGS3 + lid] = avec.sD;
+        tile[(kl*VW3 + 14) * WGS3 + lid] = avec.sE;
+        tile[(kl*VW3 + 15) * WGS3 + lid] = avec.sF;
+      #endif
+    }
 
     // Synchronizes all threads in a workgroup
     barrier(CLK_LOCAL_MEM_FENCE);
 
     // The multiply-add function (rotated)
     #pragma unroll
-    for (int kl=0; kl<WGS3/VW3; ++kl) {
-      const int k = (kwg/VW3) + kl;
-      #pragma unroll
-      for (int w=0; w<WPT3; ++w) {
-        const int gid = WPT3*get_global_id(0) + w;
-        realVFR avec = LoadMatrixAVFR(agm, k, gid, a_ld/VW3);
-        #if VW3 == 1
-          MultiplyAdd(acc[w], xlm[VW3*kl+0], avec);
-        #elif VW3 == 2
-          MultiplyAdd(acc[w], xlm[VW3*kl+0], avec.x);
-          MultiplyAdd(acc[w], xlm[VW3*kl+1], avec.y);
-        #elif VW3 == 4
-          MultiplyAdd(acc[w], xlm[VW3*kl+0], avec.x);
-          MultiplyAdd(acc[w], xlm[VW3*kl+1], avec.y);
-          MultiplyAdd(acc[w], xlm[VW3*kl+2], avec.z);
-          MultiplyAdd(acc[w], xlm[VW3*kl+3], avec.w);
-        #elif VW3 == 8
-          MultiplyAdd(acc[w], xlm[VW3*kl+0], avec.s0);
-          MultiplyAdd(acc[w], xlm[VW3*kl+1], avec.s1);
-          MultiplyAdd(acc[w], xlm[VW3*kl+2], avec.s2);
-          MultiplyAdd(acc[w], xlm[VW3*kl+3], avec.s3);
-          MultiplyAdd(acc[w], xlm[VW3*kl+4], avec.s4);
-          MultiplyAdd(acc[w], xlm[VW3*kl+5], avec.s5);
-          MultiplyAdd(acc[w], xlm[VW3*kl+6], avec.s6);
-          MultiplyAdd(acc[w], xlm[VW3*kl+7], avec.s7);
-        #elif VW3 == 16
-          MultiplyAdd(acc[w], xlm[VW3*kl+0], avec.s0);
-          MultiplyAdd(acc[w], xlm[VW3*kl+1], avec.s1);
-          MultiplyAdd(acc[w], xlm[VW3*kl+2], avec.s2);
-          MultiplyAdd(acc[w], xlm[VW3*kl+3], avec.s3);
-          MultiplyAdd(acc[w], xlm[VW3*kl+4], avec.s4);
-          MultiplyAdd(acc[w], xlm[VW3*kl+5], avec.s5);
-          MultiplyAdd(acc[w], xlm[VW3*kl+6], avec.s6);
-          MultiplyAdd(acc[w], xlm[VW3*kl+7], avec.s7);
-          MultiplyAdd(acc[w], xlm[VW3*kl+8], avec.s8);
-          MultiplyAdd(acc[w], xlm[VW3*kl+9], avec.s9);
-          MultiplyAdd(acc[w], xlm[VW3*kl+10], avec.sA);
-          MultiplyAdd(acc[w], xlm[VW3*kl+11], avec.sB);
-          MultiplyAdd(acc[w], xlm[VW3*kl+12], avec.sC);
-          MultiplyAdd(acc[w], xlm[VW3*kl+13], avec.sD);
-          MultiplyAdd(acc[w], xlm[VW3*kl+14], avec.sE);
-          MultiplyAdd(acc[w], xlm[VW3*kl+15], avec.sF);
-        #endif
-      }
+    for (int kl=0; kl<WPT3; ++kl) {
+      const int k = kl * (WGS3/WPT3) + lid_div;
+      real aval = tile[k * WPT3 + lid_mod];
+      real xval = xlm[kl];
+      MultiplyAdd(acc, xval, aval);
     }
 
     // Synchronizes all threads in a workgroup
@@ -282,12 +284,9 @@ __kernel void XgemvFastRot(const int m, const int n,
   }
 
   // Stores the final result
-  #pragma unroll
-  for (int w=0; w<WPT3; ++w) {
-    const int gid = WPT3*get_global_id(0) + w;
-    real yval = ygm[gid*y_inc + y_offset];
-    AXPBY(ygm[gid*y_inc + y_offset], alpha, acc[w], beta, yval);
-  }
+  const int gid = get_global_id(0);
+  real yval = ygm[gid * y_inc + y_offset];
+  AXPBY(ygm[gid * y_inc + y_offset], alpha, acc, beta, yval);
 }
 
 // =================================================================================================
diff --git a/src/routines/level2/xgemv.cpp b/src/routines/level2/xgemv.cpp
index 2842ef07..e4d407c8 100644
--- a/src/routines/level2/xgemv.cpp
+++ b/src/routines/level2/xgemv.cpp
@@ -122,7 +122,7 @@ StatusCode Xgemv<T>::MatVec(const Layout layout, const Transpose a_transpose,
   }
   if (fast_kernel_rot) {
     kernel_name = "XgemvFastRot";
-    global_size = m_real / db_["WPT3"];
+    global_size = m_real;
     local_size = db_["WGS3"];
   }
 
diff --git a/src/tuning/kernels/xgemv.cpp b/src/tuning/kernels/xgemv.cpp
index 5c187d33..b69e4352 100644
--- a/src/tuning/kernels/xgemv.cpp
+++ b/src/tuning/kernels/xgemv.cpp
@@ -61,8 +61,9 @@ class TuneXgemv {
 
   // Sets the tuning parameters and their possible values
   static void SetParameters(cltune::Tuner &tuner, const size_t id) {
-    tuner.AddParameter(id, "WGS"+std::to_string(V), {64, 128, 256});
-    tuner.AddParameter(id, "WPT"+std::to_string(V), {1, 2, 4});
+    tuner.AddParameter(id, "WGS"+std::to_string(V), {32, 64, 128, 256});
+    if (V==1 || V==2) { tuner.AddParameter(id, "WPT"+std::to_string(V), {1, 2, 4}); }
+    else { tuner.AddParameter(id, "WPT"+std::to_string(V), {1, 2, 4, 8, 16, 32}); }
     if (V==2 || V==3) { tuner.AddParameter(id, "VW"+std::to_string(V), {1, 2, 4, 8}); }
   }
 
@@ -74,8 +75,14 @@ class TuneXgemv {
     }
   }
   static void SetLocalMemorySize(cltune::Tuner &tuner, const size_t id, const Arguments<T> &args) {
-    auto LocalMemorySize = [args] (std::vector<size_t> v) { return v[0]*GetBytes(args.precision); };
-    tuner.SetLocalMemoryUsage(id, LocalMemorySize, {"WGS"+std::to_string(V)});
+    if (V==1 || V==2) {
+      auto LocalMemorySize = [args] (std::vector<size_t> v) { return v[0]*GetBytes(args.precision); };
+      tuner.SetLocalMemoryUsage(id, LocalMemorySize, {"WGS"+std::to_string(V)});
+    }
+    else {
+      auto LocalMemorySize = [args] (std::vector<size_t> v) { return (v[0]*v[1] + v[1])*GetBytes(args.precision); };
+      tuner.SetLocalMemoryUsage(id, LocalMemorySize, {"WGS"+std::to_string(V), "WPT"+std::to_string(V)});
+    }
   }
 
   // Sets the base thread configuration
@@ -89,7 +96,10 @@ class TuneXgemv {
   static TransformVector MulLocal() { return {{"WGS"+std::to_string(V)}}; }
   static TransformVector DivLocal() { return {}; }
   static TransformVector MulGlobal() { return {}; }
-  static TransformVector DivGlobal() { return {{"WPT"+std::to_string(V)}}; }
+  static TransformVector DivGlobal() {
+    if (V==1 || V==2) return {{"WPT"+std::to_string(V)}};
+    return {};
+  }
 
   // Sets the kernel's arguments
   static void SetArguments(cltune::Tuner &tuner, const Arguments<T> &args,
-- 
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