From 1d875f33fe9ee512644eb069ea59e1b2bd504652 Mon Sep 17 00:00:00 2001
From: couriersud <couriersud@arcor.de>
Date: Thu, 20 Aug 2015 00:31:18 +0200
Subject: [PATCH] Increase performance from 53% to 69% for matrix size around
 30x30. These matrices are e.g. used in congo bongo without optimisation. (nw)

---
 nl_examples/congo_bongo.c              |  2 +-
 src/emu/netlist/solver/nld_ms_direct.h | 60 +++++++++++++++-----------
 src/emu/netlist/solver/nld_solver.h    |  3 +-
 3 files changed, 39 insertions(+), 26 deletions(-)

diff --git a/nl_examples/congo_bongo.c b/nl_examples/congo_bongo.c
index b227d742d44..facd4054c00 100644
--- a/nl_examples/congo_bongo.c
+++ b/nl_examples/congo_bongo.c
@@ -101,7 +101,7 @@ NETLIST_START(dummy)
 	PARAM(XU13.D.MODEL, "MB3614(TYPE=1)")
 #endif
 
-#if 0
+#if 1
 	OPTIMIZE_FRONTIER(C51.1, RES_K(20), 50)
 	OPTIMIZE_FRONTIER(R77.2, RES_K(20), 50)
 
diff --git a/src/emu/netlist/solver/nld_ms_direct.h b/src/emu/netlist/solver/nld_ms_direct.h
index 2ee7a939e9d..fa570995f36 100644
--- a/src/emu/netlist/solver/nld_ms_direct.h
+++ b/src/emu/netlist/solver/nld_ms_direct.h
@@ -265,6 +265,33 @@ ATTR_COLD void matrix_solver_direct_t<m_N, _storage_N>::vsetup(analog_net_t::lis
 		psort_list(t->m_nz);
 	}
 
+	/* create a list of non zero elements below diagonal k
+	 * This should reduce cache misses ...
+	 */
+
+	bool touched[_storage_N][_storage_N] = { false };
+	for (unsigned k = 0; k < N(); k++)
+	{
+		m_terms[k]->m_nzbd.clear();
+		for (unsigned j = 0; j < m_terms[k]->m_nz.size(); j++)
+			touched[k][m_terms[k]->m_nz[j]] = true;
+	}
+
+	for (unsigned k = 0; k < N(); k++)
+	{
+		for (unsigned row = k + 1; row < N(); row++)
+		{
+			if (touched[row][k])
+			{
+				if (!m_terms[k]->m_nzbd.contains(row))
+					m_terms[k]->m_nzbd.add(row);
+				for (unsigned col = k; col < N(); col++)
+					if (touched[k][col])
+						touched[row][col] = true;
+			}
+		}
+	}
+
 	if (0)
 		for (unsigned k = 0; k < N(); k++)
 		{
@@ -393,37 +420,22 @@ ATTR_HOT void matrix_solver_direct_t<m_N, _storage_N>::LE_solve()
 		{
 			/* FIXME: Singular matrix? */
 			const nl_double f = 1.0 / A(i,i);
-			const unsigned *p = m_terms[i]->m_nzrd.data();
+			const unsigned * RESTRICT const p = m_terms[i]->m_nzrd.data();
 			const unsigned e = m_terms[i]->m_nzrd.size();
 
 			/* Eliminate column i from row j */
 
-			for (unsigned j = i + 1; j < kN; j++)
+			const unsigned * RESTRICT const pb = m_terms[i]->m_nzbd.data();
+			const unsigned eb = m_terms[i]->m_nzbd.size();
+			for (unsigned jb = 0; jb < eb; jb++)
 			{
-				if (A(j,i) != NL_FCONST(0.0))
+				const unsigned j = pb[jb];
+				const nl_double f1 = - A(j,i) * f;
+				for (unsigned k = 0; k < e; k++)
 				{
-					const nl_double f1 = - A(j,i) * f;
-	#if 0
-					/*  The code below is 30% faster than the original
-					 *  implementation which is given here for reference.
-					 *
-					 *  for (unsigned k = i + 1; k < kN; k++)
-					 *      m_A[j][k] = m_A[j][k] + m_A[i][k] * f1;
-					 */
-					double * RESTRICT d = &m_A[j][i+1];
-					const double * RESTRICT s = &m_A[i][i+1];
-					const int e = kN - i - 1;
-					for (int k = 0; k < e; k++)
-						d[k] = d[k] + s[k] * f1;
-	#else
-					for (unsigned k = 0; k < e; k++)
-					{
-						const unsigned pk = p[k];
-						A(j,pk) += A(i,pk) * f1;
-					}
-	#endif
-					m_RHS[j] += m_RHS[i] * f1;
+					A(j,p[k]) += A(i,p[k]) * f1;
 				}
+				m_RHS[j] += m_RHS[i] * f1;
 			}
 		}
 	}
diff --git a/src/emu/netlist/solver/nld_solver.h b/src/emu/netlist/solver/nld_solver.h
index 19dfa87ed11..cf03708582f 100644
--- a/src/emu/netlist/solver/nld_solver.h
+++ b/src/emu/netlist/solver/nld_solver.h
@@ -84,8 +84,9 @@ class terms_t
 
 	unsigned m_railstart;
 
-	plist_t<unsigned> m_nzrd; /* non zero right of the diagonal for elimination */
 	plist_t<unsigned> m_nz;   /* all non zero for multiplication */
+	plist_t<unsigned> m_nzrd; /* non zero right of the diagonal for elimination */
+	plist_t<unsigned> m_nzbd; /* non zero below of the diagonal for elimination */
 private:
 	plist_t<terminal_t *> m_term;
 	plist_t<int> m_net_other;