Merge pull request QMCPACK#4710 from camelto2/spl_rotation_with_blas

SplineC2C/R2R rotation with BLAS
amandadumi · Aug 28, 2023 · 6c7b0d3 · 6c7b0d3
2 parents 283f243 + 91adaa9
commit 6c7b0d3
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Showing 4 changed files with 58 additions and 34 deletions.
diff --git a/src/QMCWaveFunctions/BsplineFactory/SplineC2C.cpp b/src/QMCWaveFunctions/BsplineFactory/SplineC2C.cpp
@@ -17,6 +17,7 @@
 #include "spline2/MultiBsplineEval.hpp"
 #include "QMCWaveFunctions/BsplineFactory/contraction_helper.hpp"
 #include "CPU/math.hpp"
+#include "CPU/BLAS.hpp"
 
 namespace qmcplusplus
 {
@@ -57,7 +58,7 @@ void SplineC2C<ST>::storeParamsBeforeRotation()
 {
   const auto spline_ptr     = SplineInst->getSplinePtr();
   const auto coefs_tot_size = spline_ptr->coefs_size;
-  coef_copy_                = std::make_shared<std::vector<RealType>>(coefs_tot_size);
+  coef_copy_                = std::make_shared<std::vector<ST>>(coefs_tot_size);
 
   std::copy_n(spline_ptr->coefs, coefs_tot_size, coef_copy_->begin());
 }
@@ -120,27 +121,41 @@ void SplineC2C<ST>::applyRotation(const ValueMatrix& rot_mat, bool use_stored_co
     std::copy_n(spl_coefs, coefs_tot_size, coef_copy_->begin());
   }
 
-  for (int i = 0; i < basis_set_size; i++)
-    for (int j = 0; j < OrbitalSetSize; j++)
-    {
-      // cur_elem points to the real componend of the coefficient.
-      // Imag component is adjacent in memory.
-      const auto cur_elem = Nsplines * i + 2 * j;
-      ST newval_r{0.};
-      ST newval_i{0.};
-      for (auto k = 0; k < OrbitalSetSize; k++)
+  if constexpr (std::is_same_v<ST, RealType>)
+  {
+    //if ST is double, go ahead and use blas to make things faster
+    //Note that Nsplines needs to be divided by 2 since spl_coefs and coef_copy_ are stored as reals.
+    //Also casting them as ValueType so they are complex to do the correct gemm
+    BLAS::gemm('N', 'N', OrbitalSetSize, basis_set_size, OrbitalSetSize, ValueType(1.0, 0.0), rot_mat.data(),
+               OrbitalSetSize, (ValueType*)coef_copy_->data(), Nsplines / 2, ValueType(0.0, 0.0),
+               (ValueType*)spl_coefs, Nsplines / 2);
+  }
+  else
+  {
+    // if ST is float, RealType is double and ValueType is std::complex<double> for C2C
+    // Just use naive matrix multiplication in order to avoid losing precision on rotation matrix
+    for (IndexType i = 0; i < basis_set_size; i++)
+      for (IndexType j = 0; j < OrbitalSetSize; j++)
       {
-        const auto index = Nsplines * i + 2 * k;
-        ST zr            = (*coef_copy_)[index];
-        ST zi            = (*coef_copy_)[index + 1];
-        ST wr            = rot_mat[k][j].real();
-        ST wi            = rot_mat[k][j].imag();
-        newval_r += zr * wr - zi * wi;
-        newval_i += zr * wi + zi * wr;
+        // cur_elem points to the real componend of the coefficient.
+        // Imag component is adjacent in memory.
+        const auto cur_elem = Nsplines * i + 2 * j;
+        ST newval_r{0.};
+        ST newval_i{0.};
+        for (IndexType k = 0; k < OrbitalSetSize; k++)
+        {
+          const auto index = Nsplines * i + 2 * k;
+          ST zr            = (*coef_copy_)[index];
+          ST zi            = (*coef_copy_)[index + 1];
+          ST wr            = rot_mat[k][j].real();
+          ST wi            = rot_mat[k][j].imag();
+          newval_r += zr * wr - zi * wi;
+          newval_i += zr * wi + zi * wr;
+        }
+        spl_coefs[cur_elem]     = newval_r;
+        spl_coefs[cur_elem + 1] = newval_i;
       }
-      spl_coefs[cur_elem]     = newval_r;
-      spl_coefs[cur_elem + 1] = newval_i;
-    }
+  }
 }
 
 template<typename ST>

diff --git a/src/QMCWaveFunctions/BsplineFactory/SplineC2C.h b/src/QMCWaveFunctions/BsplineFactory/SplineC2C.h
@@ -64,7 +64,7 @@ class SplineC2C : public BsplineSet
   std::shared_ptr<MultiBspline<ST>> SplineInst;
 
   ///Copy of original splines for orbital rotation
-  std::shared_ptr<std::vector<RealType>> coef_copy_;
+  std::shared_ptr<std::vector<ST>> coef_copy_;
 
   vContainer_type mKK;
   VectorSoaContainer<ST, 3> myKcart;

diff --git a/src/QMCWaveFunctions/BsplineFactory/SplineR2R.cpp b/src/QMCWaveFunctions/BsplineFactory/SplineR2R.cpp
@@ -17,6 +17,7 @@
 #include "SplineR2R.h"
 #include "spline2/MultiBsplineEval.hpp"
 #include "QMCWaveFunctions/BsplineFactory/contraction_helper.hpp"
+#include "Platforms/CPU/BLAS.hpp"
 
 namespace qmcplusplus
 {
@@ -56,7 +57,7 @@ void SplineR2R<ST>::storeParamsBeforeRotation()
 {
   const auto spline_ptr     = SplineInst->getSplinePtr();
   const auto coefs_tot_size = spline_ptr->coefs_size;
-  coef_copy_                = std::make_shared<std::vector<RealType>>(coefs_tot_size);
+  coef_copy_                = std::make_shared<std::vector<ST>>(coefs_tot_size);
 
   std::copy_n(spline_ptr->coefs, coefs_tot_size, coef_copy_->begin());
 }
@@ -120,20 +121,28 @@ void SplineR2R<ST>::applyRotation(const ValueMatrix& rot_mat, bool use_stored_co
     std::copy_n(spl_coefs, coefs_tot_size, coef_copy_->begin());
   }
 
-  // Apply rotation the dumb way b/c I can't get BLAS::gemm to work...
-  for (auto i = 0; i < BasisSetSize; i++)
+
+  if constexpr (std::is_same_v<ST, RealType>)
   {
-    for (auto j = 0; j < OrbitalSetSize; j++)
-    {
-      const auto cur_elem = Nsplines * i + j;
-      auto newval{0.};
-      for (auto k = 0; k < OrbitalSetSize; k++)
+    //Here, ST should be equal to ValueType, which will be double for R2R. Using BLAS to make things faster
+    BLAS::gemm('N', 'N', OrbitalSetSize, BasisSetSize, OrbitalSetSize, ST(1.0), rot_mat.data(), OrbitalSetSize,
+               coef_copy_->data(), Nsplines, ST(0.0), spl_coefs, Nsplines);
+  }
+  else
+  {
+    //Here, ST is float but ValueType is double for R2R. Due to issues with type conversions, just doing naive matrix multiplication in this case to not lose precision on rot_mat
+    for (IndexType i = 0; i < BasisSetSize; i++)
+      for (IndexType j = 0; j < OrbitalSetSize; j++)
       {
-        const auto index = i * Nsplines + k;
-        newval += (*coef_copy_)[index] * rot_mat[k][j];
+        const auto cur_elem = Nsplines * i + j;
+        FullPrecValueType newval{0.};
+        for (IndexType k = 0; k < OrbitalSetSize; k++)
+        {
+          const auto index = i * Nsplines + k;
+          newval += (*coef_copy_)[index] * rot_mat[k][j];
+        }
+        spl_coefs[cur_elem] = newval;
       }
-      spl_coefs[cur_elem] = newval;
-    }
   }
 }
 

diff --git a/src/QMCWaveFunctions/BsplineFactory/SplineR2R.h b/src/QMCWaveFunctions/BsplineFactory/SplineR2R.h
@@ -59,7 +59,7 @@ class SplineR2R : public BsplineSet
   std::shared_ptr<MultiBspline<ST>> SplineInst;
 
   ///Copy of original splines for orbital rotation
-  std::shared_ptr<std::vector<RealType>> coef_copy_;
+  std::shared_ptr<std::vector<ST>> coef_copy_;
 
   ///thread private ratios for reduction when using nested threading, numVP x numThread
   Matrix<TT> ratios_private;