From 07eed363fe9f2d6287db674a44ef4353980b7256 Mon Sep 17 00:00:00 2001
From: Ray Speth <speth@mit.edu>
Date: Tue, 15 May 2018 18:32:06 -0400
Subject: [PATCH] Use std::sort to eliminate need for vcs_optMax

---
 include/cantera/equil/vcs_internal.h | 11 -----------
 src/equil/vcs_report.cpp             | 24 +++++++-----------------
 src/equil/vcs_util.cpp               | 25 -------------------------
 3 files changed, 7 insertions(+), 53 deletions(-)

diff --git a/include/cantera/equil/vcs_internal.h b/include/cantera/equil/vcs_internal.h
index 50b11d7f7..905784ef8 100644
--- a/include/cantera/equil/vcs_internal.h
+++ b/include/cantera/equil/vcs_internal.h
@@ -90,17 +90,6 @@ typedef double(*VCS_FUNC_PTR)(double xval, double Vtarget,
  */
 double vcs_l2norm(const vector_fp& vec);
 
-//! Finds the location of the maximum component in a double vector
-/*!
- * @param x pointer to a vector of doubles
- * @param xSize pointer to a vector of doubles used as a multiplier to x[]
- *              before making the decision. Ignored if set to NULL.
- * @param j lowest index to search from
- * @param n highest index to search from
- * @returns index of the greatest value on X(i) searched, j <= i < n
- */
-size_t vcs_optMax(const double* x, const double* xSize, size_t j, size_t n);
-
 //! Returns a const char string representing the type of the species given by
 //! the first argument
 /*!
diff --git a/src/equil/vcs_report.cpp b/src/equil/vcs_report.cpp
index 54deabed6..c0718b568 100644
--- a/src/equil/vcs_report.cpp
+++ b/src/equil/vcs_report.cpp
@@ -12,24 +12,14 @@ namespace Cantera
 int VCS_SOLVE::vcs_report(int iconv)
 {
     bool inertYes = false;
-    std::vector<size_t> sortindex(m_nsp, 0);
-    vector_fp xy(m_nsp, 0.0);
 
     // SORT DEPENDENT SPECIES IN DECREASING ORDER OF MOLES
-    for (size_t i = 0; i < m_nsp; ++i) {
-        sortindex[i] = i;
-        xy[i] = m_molNumSpecies_old[i];
-    }
-
-    // Sort the XY vector, the mole fraction vector, and the sort index vector,
-    // sortindex, according to the magnitude of the mole fraction vector.
-    for (size_t i = m_numComponents; i < m_numSpeciesRdc; ++i) {
-        size_t k = vcs_optMax(&xy[0], 0, i, m_numSpeciesRdc);
-        if (k != i) {
-            std::swap(xy[k], xy[i]);
-            std::swap(sortindex[k], sortindex[i]);
-        }
+    std::vector<std::pair<double, size_t>> x_order;
+    for (size_t i = 0; i < m_nsp; i++) {
+        x_order.push_back({-m_molNumSpecies_old[i], i});
     }
+    std::sort(x_order.begin() + m_numComponents,
+              x_order.begin() + m_numSpeciesRdc);
 
     vcs_setFlagsVolPhases(false, VCS_STATECALC_OLD);
     vcs_dfe(VCS_STATECALC_OLD, 0, 0, m_nsp);
@@ -71,7 +61,7 @@ int VCS_SOLVE::vcs_report(int iconv)
         plogf("\n");
     }
     for (size_t i = m_numComponents; i < m_numSpeciesRdc; ++i) {
-        size_t j = sortindex[i];
+        size_t j = x_order[i].second;
         plogf(" %-12.12s", m_speciesName[j]);
         writeline(' ', 13, false);
 
@@ -239,7 +229,7 @@ int VCS_SOLVE::vcs_report(int iconv)
     plogf("|  (MolNum ChemPot)|");
     writeline('-', 147, true, true);
     for (size_t i = 0; i < m_nsp; ++i) {
-        size_t j = sortindex[i];
+        size_t j = x_order[i].second;
         size_t pid = m_phaseID[j];
         plogf(" %-12.12s", m_speciesName[j]);
         plogf(" %14.7E ", m_molNumSpecies_old[j]);
diff --git a/src/equil/vcs_util.cpp b/src/equil/vcs_util.cpp
index 66c60eb9b..6f77d5b43 100644
--- a/src/equil/vcs_util.cpp
+++ b/src/equil/vcs_util.cpp
@@ -30,31 +30,6 @@ double vcs_l2norm(const vector_fp& vec)
     return std::sqrt(sum / vec.size());
 }
 
-size_t vcs_optMax(const double* x, const double* xSize, size_t j, size_t n)
-{
-    size_t largest = j;
-    double big = x[j];
-    if (xSize) {
-        assert(xSize[j] > 0.0);
-        big *= xSize[j];
-        for (size_t i = j + 1; i < n; ++i) {
-            assert(xSize[i] > 0.0);
-            if ((x[i] * xSize[i]) > big) {
-                largest = i;
-                big = x[i] * xSize[i];
-            }
-        }
-    } else {
-        for (size_t i = j + 1; i < n; ++i) {
-            if (x[i] > big) {
-                largest = i;
-                big = x[i];
-            }
-        }
-    }
-    return largest;
-}
-
 const char* vcs_speciesType_string(int speciesStatus, int length)
 {
     switch (speciesStatus) {