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40 #include "gen_maxwell_velocities.h"
44 #include "gromacs/math/units.h"
45 #include "gromacs/math/vec.h"
46 #include "gromacs/math/vectypes.h"
47 #include "gromacs/random/tabulatednormaldistribution.h"
48 #include "gromacs/random/threefry.h"
49 #include "gromacs/topology/mtop_util.h"
50 #include "gromacs/topology/topology.h"
51 #include "gromacs/utility/fatalerror.h"
52 #include "gromacs/utility/logger.h"
53 #include "gromacs/utility/smalloc.h"
55 static void low_mspeed(real tempi, gmx_mtop_t* mtop, rvec v[], gmx::ThreeFry2x64<>* rng, const gmx::MDLogger& logger)
60 gmx::TabulatedNormalDistribution<real> normalDist;
62 boltz = BOLTZ * tempi;
65 for (const AtomProxy atomP : AtomRange(*mtop))
67 const t_atom& local = atomP.atom();
68 int i = atomP.globalAtomNumber();
73 real sd = std::sqrt(boltz / mass);
74 for (int m = 0; (m < DIM); m++)
76 v[i][m] = sd * normalDist(*rng);
77 ekin += 0.5 * mass * v[i][m] * v[i][m];
82 temp = (2.0 * ekin) / (nrdf * BOLTZ);
85 real scal = std::sqrt(tempi / temp);
86 for (int i = 0; (i < mtop->natoms); i++)
88 for (int m = 0; (m < DIM); m++)
96 .appendTextFormatted("Velocities were taken from a Maxwell distribution at %g K", tempi);
100 "Velocities were taken from a Maxwell distribution\n"
101 "Initial generated temperature: %12.5e (scaled to: %12.5e)\n",
107 void maxwell_speed(real tempi, unsigned int seed, gmx_mtop_t* mtop, rvec v[], const gmx::MDLogger& logger)
112 seed = static_cast<int>(gmx::makeRandomSeed());
115 .appendTextFormatted("Using random seed %u for generating velocities", seed);
117 gmx::ThreeFry2x64<> rng(seed, gmx::RandomDomain::MaxwellVelocities);
119 low_mspeed(tempi, mtop, v, &rng, logger);
122 static real calc_cm(int natoms, const real mass[], rvec x[], rvec v[], rvec xcm, rvec vcm, rvec acm, matrix L)
132 for (i = 0; (i < natoms); i++)
136 cprod(x[i], v[i], a0);
137 for (m = 0; (m < DIM); m++)
139 xcm[m] += m0 * x[i][m]; /* c.o.m. position */
140 vcm[m] += m0 * v[i][m]; /* c.o.m. velocity */
141 acm[m] += m0 * a0[m]; /* rotational velocity around c.o.m. */
145 for (m = 0; (m < DIM); m++)
149 acm[m] -= a0[m] / tm;
152 #define PVEC(str, v) \
153 fprintf(log, "%s[X]: %10.5e %s[Y]: %10.5e %s[Z]: %10.5e\n", str, (v)[0], str, (v)[1], str, (v)[2])
161 for (i = 0; (i < natoms); i++)
164 for (m = 0; (m < DIM); m++)
166 dx[m] = x[i][m] - xcm[m];
168 L[XX][XX] += dx[XX] * dx[XX] * m0;
169 L[XX][YY] += dx[XX] * dx[YY] * m0;
170 L[XX][ZZ] += dx[XX] * dx[ZZ] * m0;
171 L[YY][YY] += dx[YY] * dx[YY] * m0;
172 L[YY][ZZ] += dx[YY] * dx[ZZ] * m0;
173 L[ZZ][ZZ] += dx[ZZ] * dx[ZZ] * m0;
184 void stop_cm(const gmx::MDLogger gmx_unused& logger, int natoms, real mass[], rvec x[], rvec v[])
191 GMX_LOG(logger.info).asParagraph().appendTextFormatted("stopping center of mass motion...");
193 (void)calc_cm(natoms, mass, x, v, xcm, vcm, acm, L);
195 /* Subtract center of mass velocity */
196 for (i = 0; (i < natoms); i++)
198 for (m = 0; (m < DIM); m++)