add unit test framework for pair, bond, angle styles from progguide branch

unittest/force-styles/error_stats.cpp

@@ -0,0 +1,60 @@
+/* ----------------------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   http://lammps.sandia.gov, Sandia National Laboratories
+   Steve Plimpton, sjplimp@sandia.gov
+
+   Copyright (2003) Sandia Corporation.  Under the terms of Contract
+   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
+   certain rights in this software.  This software is distributed under
+   the GNU General Public License.
+
+   See the README file in the top-level LAMMPS directory.
+------------------------------------------------------------------------- */
+
+#include "error_stats.h"
+#include <iostream>
+#include <string>
+#include <cmath>
+
+void ErrorStats::reset() {
+    num = 0;
+    maxidx = -1;
+    sum = sumsq = maxerr =0.0;
+}
+
+void ErrorStats::add(const double &val) {
+    ++num;
+    if (val > maxerr) {
+        maxidx = num;
+        maxerr = val;
+    }
+    sum += val;
+    sumsq += val*val;
+}
+
+double ErrorStats::avg() const {
+    return (num > 0) ? sum/num : 0.0;
+}
+
+double ErrorStats::dev() const {
+    return (num > 0) ? sqrt(sumsq/num - sum/num*sum/num) : 0.0;
+}
+
+std::ostream &operator<<(std::ostream &out, const ErrorStats &stats)
+{
+    const std::ios_base::fmtflags flags = out.flags();
+    const std::streamsize width = out.width(10);
+    const std::streamsize prec = out.precision(3);
+
+    out << std::scientific
+        << "Average: " << stats.avg()
+        << " StdDev: " << stats.dev()
+        << " MaxErr: " << stats.max();
+
+    out.precision(prec);
+    out.width(width);
+    out.flags(flags);
+
+    return out << " @ item: " << stats.idx();
+}
+