From 2fb64578aa31d35e26c18f8c44e041c5daac9982 Mon Sep 17 00:00:00 2001
From: Gael Guennebaud <g.gael@free.fr>
Date: Mon, 28 Apr 2014 16:16:29 +0200
Subject: Add a small benchmark to compare dense solvers for small to large
 problems.

---
 bench/dense_solvers.cpp | 76 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 bench/dense_solvers.cpp

diff --git a/bench/dense_solvers.cpp b/bench/dense_solvers.cpp
new file mode 100644
index 000000000..f37a8bb5f
--- /dev/null
+++ b/bench/dense_solvers.cpp
@@ -0,0 +1,76 @@
+#include <iostream>
+#include "BenchTimer.h"
+#include <Eigen/Dense>
+#include <map>
+#include <string>
+using namespace Eigen;
+
+std::map<std::string,Array<float,1,4> > results;
+
+template<typename Scalar,int Size>
+void bench(int id, int size = Size)
+{
+  typedef Matrix<Scalar,Size,Size> Mat;
+  Mat A(size,size);
+  A.setRandom();
+  A = A*A.adjoint();
+  BenchTimer t_llt, t_ldlt, t_lu, t_fplu, t_qr, t_cpqr, t_fpqr, t_jsvd;
+  
+  int tries = 3;
+  int rep = 1000/size;
+  if(rep==0) rep = 1;
+  rep = rep*rep;
+  
+  LLT<Mat> llt(A);
+  LDLT<Mat> ldlt(A);
+  PartialPivLU<Mat> lu(A);
+  FullPivLU<Mat> fplu(A);
+  HouseholderQR<Mat> qr(A);
+  ColPivHouseholderQR<Mat> cpqr(A);
+  FullPivHouseholderQR<Mat> fpqr(A);
+  JacobiSVD<Mat> jsvd(A.rows(),A.cols());
+  
+  BENCH(t_llt, tries, rep, llt.compute(A));
+  BENCH(t_ldlt, tries, rep, ldlt.compute(A));
+  BENCH(t_lu, tries, rep, lu.compute(A));
+  BENCH(t_fplu, tries, rep, fplu.compute(A));
+  BENCH(t_qr, tries, rep, qr.compute(A));
+  BENCH(t_cpqr, tries, rep, cpqr.compute(A));
+  BENCH(t_fpqr, tries, rep, fpqr.compute(A));
+  if(size<500) // JacobiSVD is really too slow for too large matrices
+    BENCH(t_jsvd, tries, rep, jsvd.compute(A,ComputeFullU|ComputeFullV));
+  
+  results["LLT"][id] = t_llt.best();
+  results["LDLT"][id] = t_ldlt.best();
+  results["PartialPivLU"][id] = t_lu.best();
+  results["FullPivLU"][id] = t_fplu.best();
+  results["HouseholderQR"][id] = t_qr.best();
+  results["ColPivHouseholderQR"][id] = t_cpqr.best();
+  results["FullPivHouseholderQR"][id] = t_fpqr.best();
+  results["JacobiSVD"][id] = size<500 ? t_jsvd.best() : 0;
+}
+
+int main()
+{
+  const int small = 8;
+  const int medium = 100;
+  const int large = 1000;
+  const int xl = 4000;
+  
+  bench<float,small>(0);
+  bench<float,Dynamic>(1,medium);
+  bench<float,Dynamic>(2,large);
+  bench<float,Dynamic>(3,xl);
+  
+  IOFormat fmt(3, 0, " \t", "\n", "", "");
+  
+  std::cout << "solver/size               " << small << "\t" << medium << "\t" << large << "\t" << xl << "\n";
+  std::cout << "LLT                 (ms)  " << (results["LLT"]/1000.).format(fmt) << "\n";
+  std::cout << "LDLT                 (%)  " << (results["LDLT"]/results["LLT"]).format(fmt) << "\n";
+  std::cout << "PartialPivLU         (%)  " << (results["PartialPivLU"]/results["LLT"]).format(fmt) << "\n";
+  std::cout << "FullPivLU            (%)  " << (results["FullPivLU"]/results["LLT"]).format(fmt) << "\n";
+  std::cout << "HouseholderQR        (%)  " << (results["HouseholderQR"]/results["LLT"]).format(fmt) << "\n";
+  std::cout << "ColPivHouseholderQR  (%)  " << (results["ColPivHouseholderQR"]/results["LLT"]).format(fmt) << "\n";
+  std::cout << "FullPivHouseholderQR (%)  " << (results["FullPivHouseholderQR"]/results["LLT"]).format(fmt) << "\n";
+  std::cout << "JacobiSVD            (%)  " << (results["JacobiSVD"]/results["LLT"]).format(fmt) << "\n";
+}
-- 
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