Merge branch 'master' into ipo

AUTHORS

@@ -3,3 +3,8 @@ Matthieu Schaller       matthieu.schaller@durham.ac.uk
 Aidan Chalk             aidan.chalk@durham.ac.uk
 Peter W. Draper         p.w.draper@durham.ac.uk
 Bert Vandenbrouck       bert.vandenbroucke@gmail.com
+James S. Willis 	james.s.willis@durham.ac.uk
+John A. Regan 		john.a.regan@durham.ac.uk
+Angus Lepper		angus.lepper@ed.ac.uk
+Tom Theuns 		tom.theuns@durham.ac.uk
+Richard G. Bower	r.g.bower@durham.ac.uk

INSTALL.swift

@@ -75,26 +75,33 @@ SWIFT depends on a number of third party libraries that should be available
 before you can build it.
 
 
-HDF5: a HDF5 library is required to read and write particle data. One of the
-commands "h5cc" or "h5pcc" should be available. If "h5pcc" is located them a
-parallel HDF5 built for the version of MPI located should be provided. If
-the command is not available then it can be located using the "--with-hfd5"
-configure option. The value should be the full path to the "h5cc" or "h5pcc"
-commands.
+HDF5: a HDF5 library (v. 1.8.x or higher) is required to read and write
+particle data. One of the commands "h5cc" or "h5pcc" should be
+available. If "h5pcc" is located them a parallel HDF5 built for the version
+of MPI located should be provided. If the command is not available then it
+can be located using the "--with-hfd5" configure option. The value should
+be the full path to the "h5cc" or "h5pcc" commands.
 
 
-MPI: an optional MPI library that fully supports MPI_THREAD_MULTIPLE.  
+MPI: an optional MPI library that fully supports MPI_THREAD_MULTIPLE.
 Before running configure the "mpirun" command should be available in the
 shell. If your command isn't called "mpirun" then define the "MPIRUN"
 environment variable, either in the shell or when running configure.
 
 
 METIS: a build of the METIS library can be optionally used to optimize the
-load between MPI nodes (requires an MPI library). This should be found in the
-standard installation directories, or pointed at using the "--with-metis"
-configuration option.  In this case the top-level installation directory of
-the METIS build should be given. Note to use METIS you should at least supply
-"--with-metis".
+load between MPI nodes (requires an MPI library). This should be found in
+the standard installation directories, or pointed at using the
+"--with-metis" configuration option.  In this case the top-level
+installation directory of the METIS build should be given. Note to use
+METIS you should at least supply "--with-metis".
 
 
-DOXYGEN: the doxygen library is required to create the SWIFT API documentation.
+libNUMA: a build of the NUMA library can be used to pin the threads to
+the physical core of the machine SWIFT is running on. This is not always
+necessary as the OS scheduler may do a good job at distributing the threads
+among the different cores on each computing node.
+
+
+DOXYGEN: the doxygen library is required to create the SWIFT API
+documentation.

configure.ac

@@ -16,7 +16,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 # Init the project.
-AC_INIT([SWIFT],[0.1.0])
+AC_INIT([SWIFT],[0.2.0])
 AC_CONFIG_SRCDIR([src/space.c])
 AC_CONFIG_AUX_DIR([.])
 AM_INIT_AUTOMAKE
@@ -179,10 +179,14 @@ if test "$enable_opt" = "yes" ; then
    ac_test_CFLAGS="yes"
    CFLAGS="$old_CFLAGS $CFLAGS"
 
-   # Check SSE & AVX support (some overlap with AX_CC_MAXOPT).
+   # Check SSE & AVX support (some overlap with AX_CC_MAXOPT). 
+   # Don't use the SIMD_FLAGS result with Intel compilers. The -x<code>
+   # value from AX_CC_MAXOPT should be sufficient.
    AX_EXT
    if test "$SIMD_FLAGS" != ""; then
-       CFLAGS="$CFLAGS $SIMD_FLAGS"
+       if test "$ax_cv_c_compiler_vendor" != "intel"; then
+           CFLAGS="$CFLAGS $SIMD_FLAGS"
+       fi
    fi
 fi
 
@@ -302,11 +306,13 @@ AC_CHECK_FUNC(pthread_setaffinity_np, AC_DEFINE([HAVE_SETAFFINITY],[true],
 AM_CONDITIONAL(HAVESETAFFINITY,
     [test "$ac_cv_func_pthread_setaffinity_np" = "yes"])
 
+have_numa="no"
 if test "$ac_cv_func_pthread_setaffinity_np" = "yes"; then
   # Check for libnuma.
   AC_CHECK_HEADER([numa.h])
   if test "$ac_cv_header_numa_h" = "yes"; then
     AC_CHECK_LIB([numa], [numa_available])
+    have_numa="yes"
   fi
 fi
 
@@ -367,14 +373,15 @@ AC_CONFIG_FILES([Makefile src/Makefile examples/Makefile doc/Makefile doc/Doxyfi
 
 # Report general configuration.
 AC_MSG_RESULT([
-   Compiler: $CC
-     vendor: $ax_cv_c_compiler_vendor
-    version: $ax_cv_c_compiler_version
-      flags: $CFLAGS
-   MPI enabled: $enable_mpi
-   HDF5 enabled: $with_hdf5
-       parallel: $have_parallel_hdf5
-   Metis enabled: $with_metis
+   Compiler        : $CC
+    - vendor       : $ax_cv_c_compiler_vendor
+    - version      : $ax_cv_c_compiler_version
+    - flags        : $CFLAGS
+   MPI enabled     : $enable_mpi
+   HDF5 enabled    : $with_hdf5
+    - parallel     : $have_parallel_hdf5
+   Metis enabled   : $with_metis
+   libNUMA enabled : $have_numa
 ])
 
 # Generate output.

examples/UniformBox/makeICbig.py

+###############################################################################
+ # This file is part of SWIFT.
+ # Copyright (c) 2016 Matthieu Schaller (matthieu.schaller@durham.ac.uk)
+ # 
+ # This program is free software: you can redistribute it and/or modify
+ # it under the terms of the GNU Lesser General Public License as published
+ # by the Free Software Foundation, either version 3 of the License, or
+ # (at your option) any later version.
+ # 
+ # This program is distributed in the hope that it will be useful,
+ # but WITHOUT ANY WARRANTY; without even the implied warranty of
+ # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ # GNU General Public License for more details.
+ # 
+ # You should have received a copy of the GNU Lesser General Public License
+ # along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ # 
+ ##############################################################################
+
+import h5py
+import sys
+from numpy import *
+
+# Generates a swift IC file containing a cartesian distribution of particles
+# at a constant density and pressure in a cubic box
+
+# Parameters
+periodic= 1           # 1 For periodic box
+boxSize = 1.
+L = int(sys.argv[1])  # Number of particles along one axis
+N = int(sys.argv[2])  # Write N particles at a time to avoid requiring a lot of RAM
+rho = 2.              # Density
+P = 1.                # Pressure
+gamma = 5./3.         # Gas adiabatic index
+fileName = "uniformBox_%d.hdf5"%L
+
+#---------------------------------------------------
+numPart = L**3
+mass = boxSize**3 * rho / numPart
+internalEnergy = P / ((gamma - 1.)*rho)
+
+#---------------------------------------------------
+
+n_iterations = numPart / N
+remainder = numPart % N
+
+print "Writing", numPart, "in", n_iterations, "iterations of size", N, "and a remainder of", remainder
+
+#---------------------------------------------------
+
+#File
+file = h5py.File(fileName, 'w')
+
+# Header
+grp = file.create_group("/Header")
+grp.attrs["BoxSize"] = boxSize
+grp.attrs["NumPart_Total"] =  [numPart % (long(1)<<32), 0, 0, 0, 0, 0]
+grp.attrs["NumPart_Total_HighWord"] = [numPart / (long(1)<<32), 0, 0, 0, 0, 0]
+grp.attrs["NumPart_ThisFile"] = [numPart, 0, 0, 0, 0, 0]
+grp.attrs["Time"] = 0.0
+grp.attrs["NumFilesPerSnapshot"] = 1
+grp.attrs["MassTable"] = [0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
+grp.attrs["Flag_Entropy_ICs"] = 0
+
+
+#Runtime parameters
+grp = file.create_group("/RuntimePars")
+grp.attrs["PeriodicBoundariesOn"] = periodic
+
+#Particle group
+grp = file.create_group("/PartType0")
+
+# First create the arrays in the file
+ds_v = grp.create_dataset('Velocities', (numPart, 3), 'f', chunks=True, compression="gzip")
+ds_m = grp.create_dataset('Masses', (numPart,1), 'f', chunks=True, compression="gzip")
+ds_h = grp.create_dataset('SmoothingLength', (numPart,1), 'f', chunks=True, compression="gzip")
+ds_u = grp.create_dataset('InternalEnergy', (numPart,1), 'f', chunks=True, compression="gzip")
+ds_id = grp.create_dataset('ParticleIDs', (numPart, 1), 'L', chunks=True, compression="gzip")
+ds_x = grp.create_dataset('Coordinates', (numPart, 3), 'd', chunks=True, compression="gzip")
+
+# Now loop and create parts of the dataset
+offset = 0
+for n in range(n_iterations):
+    v  = zeros((N, 3))
+    ds_v[offset:offset+N,:] = v
+    v = zeros(1)
+
+    m = full((N, 1), mass)
+    ds_m[offset:offset+N] = m
+    m = zeros(1)
+
+    h = full((N, 1), 1.1255 * boxSize / L)
+    ds_h[offset:offset+N] = h
+    h = zeros(1)
+
+    u = full((N, 1), internalEnergy)
+    ds_u[offset:offset+N] = u
+    u = zeros(1)
+
+    ids = linspace(offset, offset+N, N, endpoint=False).reshape((N,1))
+    ds_id[offset:offset+N] = ids
+    x      = ids % L;
+    y      = ((ids - x) / L) % L;
+    z      = (ids - x - L * y) / L**2;
+    ids    = zeros(1)
+    coords = zeros((N, 3))
+    coords[:,0] = z[:,0] * boxSize / L + boxSize / (2*L)
+    coords[:,1] = y[:,0] * boxSize / L + boxSize / (2*L)
+    coords[:,2] = x[:,0] * boxSize / L + boxSize / (2*L)
+    ds_x[offset:offset+N,:] = coords
+    coords  = zeros((1,3))
+
+    offset += N
+    print "Done", offset,"/", numPart, "(%.1f %%)"%(100*(float)(offset)/numPart)
+
+# And now, the remainder
+v  = zeros((remainder, 3))
+ds_v[offset:offset+remainder,:] = v
+v = zeros(1)
+
+m = full((remainder, 1), mass)
+ds_m[offset:offset+remainder] = m
+m = zeros(1)
+
+h = full((remainder, 1), 1.1255 * boxSize / L)
+ds_h[offset:offset+remainder] = h
+h = zeros(1)
+
+u = full((remainder, 1), internalEnergy)
+ds_u[offset:offset+remainder] = u
+u = zeros(1)
+
+print "Done", offset+remainder,"/", numPart
+
+ids = linspace(offset, offset+remainder, remainder, endpoint=False).reshape((remainder,1))
+ds_id[offset:offset+remainder] = ids
+x      = ids % L;
+y      = ((ids - x) / L) % L;
+z      = (ids - x - L * y) / L**2;
+coords = zeros((remainder, 3))
+coords[:,0] = z[:,0] * boxSize / L + boxSize / (2*L)
+coords[:,1] = y[:,0] * boxSize / L + boxSize / (2*L)
+coords[:,2] = x[:,0] * boxSize / L + boxSize / (2*L)
+ds_x[offset:offset+remainder,:] = coords
+
+
+
+
+
+file.close()

m4/ax_cc_maxopt.m4

@@ -125,7 +125,7 @@ if test "$ac_test_CFLAGS" != "set"; then
 		    *1?6[[aef]]?:*:*:*|*2?6[[5cef]]?:*:*:*) icc_flags="-xSSE4.2 -xS -xT -xB -xK" ;;
 		    *2?6[[ad]]?:*:*:*) icc_flags="-xAVX -SSE4.2 -xS -xT -xB -xK" ;;
 		    *3?6[[ae]]?:*:*:*) icc_flags="-xCORE-AVX-I -xAVX -SSE4.2 -xS -xT -xB -xK" ;;
-		    *3?6[[cf]]?:*:*:*|*4?6[[56]]?:*:*:*) icc_flags="-xCORE-AVX2 -xCORE-AVX-I -xAVX -SSE4.2 -xS -xT -xB -xK" ;;
+		    *3?6[[cf]]?:*:*:*|*4?6[[56]]?:*:*:*|*4?6[[ef]]?:*:*:*) icc_flags="-xCORE-AVX2 -xCORE-AVX-I -xAVX -SSE4.2 -xS -xT -xB -xK" ;;
 		    *000?f[[346]]?:*:*:*|?f[[346]]?:*:*:*|f[[346]]?:*:*:*) icc_flags="-xSSE3 -xP -xO -xN -xW -xK" ;;
 		    *00??f??:*:*:*|??f??:*:*:*|?f??:*:*:*|f??:*:*:*) icc_flags="-xSSE2 -xN -xW -xK" ;;
                   esac ;;

src/Makefile.am

@@ -46,15 +46,20 @@ AM_SOURCES = space.c runner.c queue.c task.c cell.c engine.c \
 # Include files for distribution, not installation.
 nobase_noinst_HEADERS = approx_math.h atomic.h cycle.h error.h inline.h kernel.h vector.h \
 		 runner_doiact.h runner_doiact_grav.h units.h intrinsics.h minmax.h \
-		 hydro.h hydro_io.h gravity.h \
+		 gravity.h \
 		 gravity/Default/gravity.h gravity/Default/runner_iact_grav.h \
 		 gravity/Default/gravity_part.h \
+	 	 hydro.h hydro_io.h \
 		 hydro/Minimal/hydro.h hydro/Minimal/hydro_iact.h hydro/Minimal/hydro_io.h \
                  hydro/Minimal/hydro_debug.h hydro/Minimal/hydro_part.h \
 		 hydro/Default/hydro.h hydro/Default/hydro_iact.h hydro/Default/hydro_io.h \
                  hydro/Default/hydro_debug.h hydro/Default/hydro_part.h \
 		 hydro/Gadget2/hydro.h hydro/Gadget2/hydro_iact.h hydro/Gadget2/hydro_io.h \
-                 hydro/Gadget2/hydro_debug.h hydro/Gadget2/hydro_part.h
+                 hydro/Gadget2/hydro_debug.h hydro/Gadget2/hydro_part.h \
+		 hydro/Gizmo/hydro.h hydro/Gizmo/hydro_iact.h hydro/Gizmo/hydro_io.h \
+                 hydro/Gizmo/hydro_debug.h hydro/Gizmo/hydro_part.h \
+	         riemann.h \
+		 riemann/riemann_hllc.h riemann/riemann_trrs.h riemann/riemann_exact.h
 
 # Sources and flags for regular library
 libswiftsim_la_SOURCES = $(AM_SOURCES)

src/hydro/Gadget2/hydro_iact.h

@@ -51,7 +51,7 @@ __attribute__((always_inline)) INLINE static void runner_iact_density(
   float dv[3], curlvr[3];
 
   /* Get the masses. */
-  const float mi = pj->mass;
+  const float mi = pi->mass;
   const float mj = pj->mass;
 
   /* Get r and r inverse. */

src/hydro/Gizmo/hydro_debug.h

+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Coypright (c) 2016 Matthieu Schaller (matthieu.schaller@durham.ac.uk)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ ******************************************************************************/
+
+__attribute__((always_inline))
+    INLINE static void hydro_debug_particle(struct part* p, struct xpart* xp) {
+  printf(
+      "x=[%.16e,%.16e,%.16e], "
+      "v=[%.3e,%.3e,%.3e], a=[%.3e,%.3e,%.3e], volume=%.3e\n",
+      p->x[0], p->x[1], p->x[2], p->v[0], p->v[1], p->v[2], p->a_hydro[0],
+      p->a_hydro[1], p->a_hydro[2], p->geometry.volume);
+}

src/hydro/Gizmo/hydro_io.h

+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Coypright (c) 2016 Matthieu Schaller (matthieu.schaller@durham.ac.uk)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ ******************************************************************************/
+
+/**
+ * @brief Reads the different particles to the HDF5 file
+ *
+ * @param h_grp The HDF5 group in which to read the arrays.
+ * @param N The number of particles on that MPI rank.
+ * @param N_total The total number of particles (only used in MPI mode)
+ * @param offset The offset of the particles for this MPI rank (only used in MPI
+ *mode)
+ * @param parts The particle array
+ *
+ */
+__attribute__((always_inline)) INLINE static void hydro_read_particles(
+    hid_t h_grp, int N, long long N_total, long long offset,
+    struct part* parts) {
+
+  /* Read arrays */
+  readArray(h_grp, "Coordinates", DOUBLE, N, 3, parts, N_total, offset, x,
+            COMPULSORY);
+  readArray(h_grp, "Velocities", FLOAT, N, 3, parts, N_total, offset, v,
+            COMPULSORY);
+  readArray(h_grp, "Masses", FLOAT, N, 1, parts, N_total, offset,
+            conserved.mass, COMPULSORY);
+  readArray(h_grp, "SmoothingLength", FLOAT, N, 1, parts, N_total, offset, h,
+            COMPULSORY);
+  readArray(h_grp, "InternalEnergy", FLOAT, N, 1, parts, N_total, offset,
+            primitives.P, COMPULSORY);
+  readArray(h_grp, "ParticleIDs", ULONGLONG, N, 1, parts, N_total, offset, id,
+            COMPULSORY);
+  readArray(h_grp, "Acceleration", FLOAT, N, 3, parts, N_total, offset, a_hydro,
+            OPTIONAL);
+  readArray(h_grp, "Density", FLOAT, N, 1, parts, N_total, offset,
+            primitives.rho, OPTIONAL);
+}
+
+/**
+ * @brief Writes the different particles to the HDF5 file
+ *
+ * @param h_grp The HDF5 group in which to write the arrays.
+ * @param fileName The name of the file (unsued in MPI mode).
+ * @param xmfFile The XMF file to write to (unused in MPI mode).
+ * @param N The number of particles on that MPI rank.
+ * @param N_total The total number of particles (only used in MPI mode)
+ * @param mpi_rank The MPI rank of this node (only used in MPI mode)
+ * @param offset The offset of the particles for this MPI rank (only used in MPI
+ *mode)
+ * @param parts The particle array
+ * @param us The unit system to use
+ *
+ */
+__attribute__((always_inline)) INLINE static void hydro_write_particles(
+    hid_t h_grp, char* fileName, FILE* xmfFile, int N, long long N_total,
+    int mpi_rank, long long offset, struct part* parts, struct UnitSystem* us) {
+
+  /* Write arrays */
+  writeArray(h_grp, fileName, xmfFile, "Coordinates", DOUBLE, N, 3, parts,
+             N_total, mpi_rank, offset, x, us, UNIT_CONV_LENGTH);
+  writeArray(h_grp, fileName, xmfFile, "Velocities", FLOAT, N, 3, parts,
+             N_total, mpi_rank, offset, v, us, UNIT_CONV_SPEED);
+  writeArray(h_grp, fileName, xmfFile, "Masses", FLOAT, N, 1, parts, N_total,
+             mpi_rank, offset, conserved.mass, us, UNIT_CONV_MASS);
+  writeArray(h_grp, fileName, xmfFile, "SmoothingLength", FLOAT, N, 1, parts,
+             N_total, mpi_rank, offset, h, us, UNIT_CONV_LENGTH);
+  writeArray(h_grp, fileName, xmfFile, "InternalEnergy", FLOAT, N, 1, parts,
+             N_total, mpi_rank, offset, primitives.P, us,
+             UNIT_CONV_ENTROPY_PER_UNIT_MASS);
+  writeArray(h_grp, fileName, xmfFile, "ParticleIDs", ULONGLONG, N, 1, parts,
+             N_total, mpi_rank, offset, id, us, UNIT_CONV_NO_UNITS);
+  writeArray(h_grp, fileName, xmfFile, "Acceleration", FLOAT, N, 3, parts,
+             N_total, mpi_rank, offset, a_hydro, us, UNIT_CONV_ACCELERATION);
+  writeArray(h_grp, fileName, xmfFile, "Density", FLOAT, N, 1, parts, N_total,
+             mpi_rank, offset, primitives.rho, us, UNIT_CONV_DENSITY);
+}
+
+/**
+ * @brief Writes the current model of SPH to the file
+ * @param h_grpsph The HDF5 group in which to write
+ */
+void writeSPHflavour(hid_t h_grpsph) {
+
+  /* Kernel function description */
+  writeAttribute_s(h_grpsph, "Kernel", kernel_name);
+  writeAttribute_f(h_grpsph, "Kernel eta", const_eta_kernel);
+  writeAttribute_f(h_grpsph, "Weighted N_ngb", kernel_nwneigh);
+  writeAttribute_f(h_grpsph, "Delta N_ngb", const_delta_nwneigh);
+  writeAttribute_f(h_grpsph, "Hydro gamma", const_hydro_gamma);
+
+  /* Viscosity and thermal conduction */
+  writeAttribute_s(h_grpsph, "Thermal Conductivity Model",
+                   "(No treatment) Legacy Gadget-2 as in Springel (2005)");
+  writeAttribute_s(h_grpsph, "Viscosity Model",
+                   "Legacy Gadget-2 as in Springel (2005)");
+  writeAttribute_f(h_grpsph, "Viscosity alpha", const_viscosity_alpha);
+  writeAttribute_f(h_grpsph, "Viscosity beta", 3.f);
+
+  /* Time integration properties */
+  writeAttribute_f(h_grpsph, "CFL parameter", const_cfl);
+  writeAttribute_f(h_grpsph, "Maximal ln(Delta h) change over dt",
+                   const_ln_max_h_change);
+  writeAttribute_f(h_grpsph, "Maximal Delta h change over dt",
+                   exp(const_ln_max_h_change));
+}

src/hydro/Gizmo/hydro_part.h

+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Coypright (c) 2012 Pedro Gonnet (pedro.gonnet@durham.ac.uk)
+ *                    Matthieu Schaller (matthieu.schaller@durham.ac.uk)
+ *                    Bert Vandenbroucke (bert.vandenbroucke@ugent.be)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ ******************************************************************************/
+
+/* Some standard headers. */
+#include <stdlib.h>
+
+#define GFLOAT float
+
+/* Extra particle data not needed during the computation. */
+struct xpart {
+
+  /* Old position, at last tree rebuild. */
+  double x_old[3];
+
+  /* Velocity at the last full step. */
+  float v_full[3];
+
+  /* Entropy at the half-step. */
+  float u_hdt;
+
+  /* Old density. */
+  float omega;
+
+} __attribute__((aligned(xpart_align)));
+
+/* Data of a single particle. */
+struct part {
+
+  /* Particle position. */
+  double x[3];
+
+  /* Particle velocity. */
+  float v[3];
+
+  /* Particle acceleration. */
+  float a_hydro[3];
+
+  float mass;  // MATTHIEU
+  float h_dt;
+  float rho;
+  float rho_dh;
+
+  /* Particle cutoff radius. */
+  float h;
+
+  /* Particle time of beginning of time-step. */
+  int ti_begin;
+
+  /* Particle time of end of time-step. */
+  int ti_end;
+
+  /* The primitive hydrodynamical variables */
+  struct {
+
+    /* fluid velocity */
+    GFLOAT v[3];
+
+    /* density */
+    GFLOAT rho;
+
+    /* pressure */
+    GFLOAT P;
+
+    struct {
+
+      GFLOAT rho[3];
+
+      GFLOAT v[3][3];
+
+      GFLOAT P[3];
+
+    } gradients;
+
+    struct {
+
+      /* extreme values among the neighbours */
+      GFLOAT rho[2];
+
+      GFLOAT v[3][2];
+
+      GFLOAT P[2];
+
+      /* maximal distance to all neighbouring faces */
+      float maxr;
+
+    } limiter;
+
+  } primitives;
+
+  /* The conserved hydrodynamical variables */
+  struct {
+
+    /* fluid momentum */
+    GFLOAT momentum[3];
+
+    /* fluid mass */
+    GFLOAT mass;
+
+    /* fluid energy */
+    GFLOAT energy;
+
+  } conserved;
+
+  /* Geometrical quantities used for hydro */
+  struct {
+
+    /* volume of the particle */
+    float volume;
+
+    /* gradient matrix */
+    float matrix_E[3][3];
+
+  } geometry;
+
+  struct {
+
+    float vmax;
+
+  } timestepvars;
+