Merge branch 'gamma_power_speed_up' into 'master'

Gamma power speed up

"Fix" to #185. See also the discussion in #166.

Two improvements:

 - Speed-up the calculation of x^\gamma, x^{\gamma-1} and x^-(\gamma-1) . Currently support \gamma=5/3, \gamma=4/3 and \gamma=2.
 - Write the details of the hydro scheme in the snapshots.

Branch can be removed.

See merge request !195

doc/Doxyfile.in

@@ -1428,7 +1428,7 @@ FORMULA_TRANSPARENT    = YES
 # The default value is: NO.
 # This tag requires that the tag GENERATE_HTML is set to YES.
 
-USE_MATHJAX            = NO
+USE_MATHJAX            = YES
 
 # When MathJax is enabled you can set the default output format to be used for
 # the MathJax output. See the MathJax site (see:

src/Makefile.am

@@ -54,11 +54,11 @@ 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_hydro.h kernel_gravity.h \
 		 vector.h runner_doiact.h runner_doiact_grav.h units.h intrinsics.h minmax.h kick.h \
-		 timestep.h drift.h \
+		 timestep.h drift.h adiabatic_index.h \
 		 gravity.h gravity_io.h \
 		 gravity/Default/gravity.h gravity/Default/gravity_iact.h gravity/Default/gravity_io.h \
 		 gravity/Default/gravity_debug.h gravity/Default/gravity_part.h  \
-	 	 hydro.h hydro_io.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 \

src/adiabatic_index.h

+/*******************************************************************************
+ * 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/>.
+ *
+ ******************************************************************************/
+#ifndef SWIFT_ADIABATIC_INDEX_H
+#define SWIFT_ADIABATIC_INDEX_H
+
+/* Config parameters. */
+#include "../config.h"
+
+/* Some standard headers. */
+#include <math.h>
+
+/* Local headers. */
+#include "const.h"
+#include "debug.h"
+#include "inline.h"
+
+/* First define some constants */
+#if defined(HYDRO_GAMMA_5_3)
+
+#define hydro_gamma 1.66666666666666667f
+#define hydro_gamma_minus_one 0.66666666666666667f
+#define hydro_one_over_gamma_minus_one 1.5f
+
+#elif defined(HYDRO_GAMMA_4_3)
+
+#define hydro_gamma 1.33333333333333333f
+#define hydro_gamma_minus_one 0.33333333333333333f
+#define hydro_one_over_gamma_minus_one 3.f
+
+#elif defined(HYDRO_GAMMA_2_1)
+
+#define hydro_gamma 2.f
+#define hydro_gamma_minus_one 1.f
+#define hydro_one_over_gamma_minus_one 1.f
+
+#endif
+
+/**
+ * @brief Returns the argument to the power given by the adiabatic index
+ *
+ * Computes \f$x^\gamma\f$.
+ */
+__attribute__((always_inline)) INLINE static float pow_gamma(float x) {
+
+#if defined(HYDRO_GAMMA_5_3)
+
+  const float x2 = x * x;
+  const float x5 = x2 * x2 * x;
+  return cbrtf(x5);
+
+#elif defined(HYDRO_GAMMA_4_3)
+
+  const float x2 = x * x;
+  const float x4 = x2 * x2;
+  return cbrtf(x4);
+
+#elif defined(HYDRO_GAMMA_2_1)
+
+  return x * x;
+
+#else
+
+  error("The adiabatic index is not defined !");
+  return 0.f;
+
+#endif
+}
+
+/**
+ * @brief Returns the argument to the power given by the adiabatic index minus
+ * one
+ *
+ * Computes \f$x^{(\gamma-1)}\f$.
+ */
+__attribute__((always_inline)) INLINE static float pow_gamma_minus_one(
+    float x) {
+
+#if defined(HYDRO_GAMMA_5_3)
+
+  return cbrtf(x * x);
+
+#elif defined(HYDRO_GAMMA_4_3)
+
+  return cbrtf(x);
+
+#elif defined(HYDRO_GAMMA_2_1)
+
+  return x;
+
+#else
+
+  error("The adiabatic index is not defined !");
+  return 0.f;
+
+#endif
+}
+
+/**
+ * @brief Returns one over the argument to the power given by the adiabatic
+ * index minus one
+ *
+ * Computes \f$x^{-(\gamma-1)}\f$.
+ */
+__attribute__((always_inline)) INLINE static float pow_minus_gamma_minus_one(
+    float x) {
+
+#if defined(HYDRO_GAMMA_5_3)
+
+  return 1.f / cbrtf(x * x);
+
+#elif defined(HYDRO_GAMMA_4_3)
+
+  return 1.f / cbrtf(x);
+
+#elif defined(HYDRO_GAMMA_2_1)
+
+  return 1.f / x;
+
+#else
+
+  error("The adiabatic index is not defined !");
+  return 0.f;
+
+#endif
+}
+
+#endif /* SWIFT_ADIABATIC_INDEX_H */

src/const.h

@@ -20,9 +20,6 @@
 #ifndef SWIFT_CONST_H
 #define SWIFT_CONST_H
 
-/* Hydrodynamical constants. */
-#define const_hydro_gamma (5.0f / 3.0f)
-
 /* SPH Viscosity constants. */
 #define const_viscosity_alpha 0.8f
 #define const_viscosity_alpha_min \
@@ -44,6 +41,11 @@
 #define const_G 6.672e-8f     /* Gravitational constant. */
 #define const_epsilon 0.0014f /* Gravity blending distance. */
 
+/* Hydrodynamical adiabatic index. */
+#define HYDRO_GAMMA_5_3
+//#define HYDRO_GAMMA_4_3
+//#define HYDRO_GAMMA_2_1
+
 /* Kernel function to use */
 #define CUBIC_SPLINE_KERNEL
 //#define QUARTIC_SPLINE_KERNEL

src/hydro/Default/hydro.h

@@ -17,6 +17,7 @@
  *
  ******************************************************************************/
 
+#include "adiabatic_index.h"
 #include "approx_math.h"
 
 /**
@@ -138,12 +139,11 @@ __attribute__((always_inline)) INLINE static void hydro_prepare_force(
 
   /* Compute this particle's sound speed. */
   const float u = p->u;
-  const float fc = p->force.c =
-      sqrtf(const_hydro_gamma * (const_hydro_gamma - 1.0f) * u);
+  const float fc = p->force.c = sqrtf(hydro_gamma * hydro_gamma_minus_one * u);
 
   /* Compute the P/Omega/rho2. */
   xp->omega = 1.0f + 0.3333333333f * h * p->rho_dh / p->rho;
-  p->force.POrho2 = u * (const_hydro_gamma - 1.0f) / (p->rho * xp->omega);
+  p->force.POrho2 = u * hydro_gamma_minus_one / (p->rho * xp->omega);
 
   /* Balsara switch */
   p->force.balsara = normDiv_v / (normDiv_v + normCurl_v + 0.0001f * fc * ih);
@@ -207,7 +207,7 @@ __attribute__((always_inline)) INLINE static void hydro_predict_extra(
     u = p->u *= expf(w);
 
   /* Predict gradient term */
-  p->force.POrho2 = u * (const_hydro_gamma - 1.0f) / (p->rho * xp->omega);
+  p->force.POrho2 = u * hydro_gamma_minus_one / (p->rho * xp->omega);
 }
 
 /**

src/hydro/Default/hydro_iact.h

@@ -20,6 +20,8 @@
 #ifndef SWIFT_RUNNER_IACT_H
 #define SWIFT_RUNNER_IACT_H
 
+#include "adiabatic_index.h"
+
 /**
  * @brief SPH interaction functions following the Gadget-2 version of SPH.
  *
@@ -408,7 +410,7 @@ __attribute__((always_inline)) INLINE static void runner_iact_force(
   Pi_ij *= (pi->force.balsara + pj->force.balsara);
 
   /* Thermal conductivity */
-  v_sig_u = sqrtf(2.f * (const_hydro_gamma - 1.f) *
+  v_sig_u = sqrtf(2.f * hydro_gamma_minus_one *
                   fabs(rhoi * pi->u - rhoj * pj->u) / (rhoi + rhoj));
   tc = const_conductivity_alpha * v_sig_u / (rhoi + rhoj);
   tc *= (wi_dr + wj_dr);
@@ -608,7 +610,7 @@ __attribute__((always_inline)) INLINE static void runner_iact_vec_force(
   Pi_ij.v *= (wi_dr.v + wj_dr.v);
 
   /* Thermal conductivity */
-  v_sig_u.v = vec_sqrt(vec_set1(2.f * (const_hydro_gamma - 1.f)) *
+  v_sig_u.v = vec_sqrt(vec_set1(2.f * hydro_gamma_minus_one) *
                        vec_fabs(pirho.v * piu.v - pjrho.v * pju.v) /
                        (pirho.v + pjrho.v));
   tc.v = vec_set1(const_conductivity_alpha) * v_sig_u.v / (pirho.v + pjrho.v);
@@ -721,7 +723,7 @@ __attribute__((always_inline)) INLINE static void runner_iact_nonsym_force(
   Pi_ij *= (pi->force.balsara + pj->force.balsara);
 
   /* Thermal conductivity */
-  v_sig_u = sqrtf(2.f * (const_hydro_gamma - 1.f) *
+  v_sig_u = sqrtf(2.f * hydro_gamma_minus_one *
                   fabs(rhoi * pi->u - rhoj * pj->u) / (rhoi + rhoj));
   tc = const_conductivity_alpha * v_sig_u / (rhoi + rhoj);
   tc *= (wi_dr + wj_dr);
@@ -912,7 +914,7 @@ __attribute__((always_inline)) INLINE static void runner_iact_nonsym_vec_force(
   Pi_ij.v *= (wi_dr.v + wj_dr.v);
 
   /* Thermal conductivity */
-  v_sig_u.v = vec_sqrt(vec_set1(2.f * (const_hydro_gamma - 1.f)) *
+  v_sig_u.v = vec_sqrt(vec_set1(2.f * hydro_gamma_minus_one) *
                        vec_fabs(pirho.v * piu.v - pjrho.v * pju.v) /
                        (pirho.v + pjrho.v));
   tc.v = vec_set1(const_conductivity_alpha) * v_sig_u.v / (pirho.v + pjrho.v);

src/hydro/Default/hydro_io.h

@@ -102,9 +102,6 @@ __attribute__((always_inline)) INLINE static void hydro_write_particles(
  */
 void writeSPHflavour(hid_t h_grpsph) {
 
-  /* Kernel function description */
-  writeAttribute_s(h_grpsph, "Kernel", kernel_name);
-
   /* Viscosity and thermal conduction */
   writeAttribute_s(h_grpsph, "Thermal Conductivity Model",
                    "Price (2008) without switch");

src/hydro/Gadget2/hydro.h

@@ -17,6 +17,8 @@
  *
  ******************************************************************************/
 
+#include "adiabatic_index.h"
+
 /**
  * @brief Computes the hydro time-step of a given particle
  *
@@ -132,11 +134,10 @@ __attribute__((always_inline)) INLINE static void hydro_prepare_force(
 
   /* Compute the pressure */
   const float dt = (ti_current - (p->ti_begin + p->ti_end) / 2) * timeBase;
-  p->force.pressure =
-      (p->entropy + p->entropy_dt * dt) * powf(p->rho, const_hydro_gamma);
+  p->force.pressure = (p->entropy + p->entropy_dt * dt) * pow_gamma(p->rho);
 
   /* Compute the sound speed */
-  p->force.soundspeed = sqrtf(const_hydro_gamma * p->force.pressure / p->rho);
+  p->force.soundspeed = sqrtf(hydro_gamma * p->force.pressure / p->rho);
 }
 
 /**
@@ -179,10 +180,10 @@ __attribute__((always_inline)) INLINE static void hydro_predict_extra(
   /* Drift the pressure */
   const float dt_entr = (t1 - (p->ti_begin + p->ti_end) / 2) * timeBase;
   p->force.pressure =
-      (p->entropy + p->entropy_dt * dt_entr) * powf(p->rho, const_hydro_gamma);
+      (p->entropy + p->entropy_dt * dt_entr) * pow_gamma(p->rho);
 
   /* Compute the new sound speed */
-  p->force.soundspeed = sqrtf(const_hydro_gamma * p->force.pressure / p->rho);
+  p->force.soundspeed = sqrtf(hydro_gamma * p->force.pressure / p->rho);
 }
 
 /**
@@ -195,8 +196,7 @@ __attribute__((always_inline)) INLINE static void hydro_predict_extra(
 __attribute__((always_inline)) INLINE static void hydro_end_force(
     struct part* p) {
 
-  p->entropy_dt *=
-      (const_hydro_gamma - 1.f) * powf(p->rho, -(const_hydro_gamma - 1.f));
+  p->entropy_dt *= hydro_gamma_minus_one * pow_minus_gamma_minus_one(p->rho);
 }
 
 /**
@@ -232,8 +232,8 @@ __attribute__((always_inline)) INLINE static void hydro_kick_extra(
 __attribute__((always_inline)) INLINE static void hydro_convert_quantities(
     struct part* p) {
 
-  p->entropy = (const_hydro_gamma - 1.f) * p->entropy *
-               powf(p->rho, -(const_hydro_gamma - 1.f));
+  p->entropy =
+      hydro_gamma_minus_one * p->entropy * pow_minus_gamma_minus_one(p->rho);
 }
 
 /**
@@ -247,6 +247,5 @@ __attribute__((always_inline)) INLINE static float hydro_get_internal_energy(
 
   const float entropy = p->entropy + p->entropy_dt * dt;
 
-  return entropy * powf(p->rho, const_hydro_gamma - 1.f) *
-         (1.f / (const_hydro_gamma - 1.f));
+  return entropy * pow_gamma_minus_one(p->rho) * hydro_one_over_gamma_minus_one;
 }

src/hydro/Gadget2/hydro_io.h

@@ -102,9 +102,6 @@ __attribute__((always_inline)) INLINE static void hydro_write_particles(
  */
 void writeSPHflavour(hid_t h_grpsph) {
 
-  /* Kernel function description */
-  writeAttribute_s(h_grpsph, "Kernel", kernel_name);
-
   /* Viscosity and thermal conduction */
   writeAttribute_s(h_grpsph, "Thermal Conductivity Model",
                    "(No treatment) Legacy Gadget-2 as in Springel (2005)");

src/hydro/Minimal/hydro.h

@@ -17,6 +17,7 @@
  *
  ******************************************************************************/
 
+#include "adiabatic_index.h"
 #include "approx_math.h"
 
 /**
@@ -132,7 +133,7 @@ __attribute__((always_inline)) INLINE static void hydro_end_density(
 __attribute__((always_inline)) INLINE static void hydro_prepare_force(
     struct part* p, struct xpart* xp, int ti_current, double timeBase) {
 
-  p->force.pressure = p->rho * p->u * (const_hydro_gamma - 1.f);
+  p->force.pressure = p->rho * p->u * hydro_gamma_minus_one;
 }
 
 /**
@@ -175,7 +176,7 @@ __attribute__((always_inline)) INLINE static void hydro_predict_extra(
   p->u = xp->u_full;
 
   /* Need to recompute the pressure as well */
-  p->force.pressure = p->rho * p->u * (const_hydro_gamma - 1.f);
+  p->force.pressure = p->rho * p->u * hydro_gamma_minus_one;
 }
 
 /**

src/hydro/Minimal/hydro_iact.h

@@ -19,6 +19,8 @@
 #ifndef SWIFT_RUNNER_IACT_MINIMAL_H
 #define SWIFT_RUNNER_IACT_MINIMAL_H
 
+#include "adiabatic_index.h"
+
 /**
  * @brief Minimal conservative implementation of SPH
  *
@@ -150,8 +152,8 @@ __attribute__((always_inline)) INLINE static void runner_iact_force(
                      (pi->v[2] - pj->v[2]) * dx[2];
 
   /* Compute sound speeds */
-  const float ci = sqrtf(const_hydro_gamma * pressurei / rhoi);
-  const float cj = sqrtf(const_hydro_gamma * pressurej / rhoj);
+  const float ci = sqrtf(hydro_gamma * pressurei / rhoi);
+  const float cj = sqrtf(hydro_gamma * pressurej / rhoj);
   const float v_sig = ci + cj;
 
   /* SPH acceleration term */
@@ -233,8 +235,8 @@ __attribute__((always_inline)) INLINE static void runner_iact_nonsym_force(
                      (pi->v[2] - pj->v[2]) * dx[2];
 
   /* Compute sound speeds */
-  const float ci = sqrtf(const_hydro_gamma * pressurei / rhoi);
-  const float cj = sqrtf(const_hydro_gamma * pressurej / rhoj);
+  const float ci = sqrtf(hydro_gamma * pressurei / rhoi);
+  const float cj = sqrtf(hydro_gamma * pressurej / rhoj);
   const float v_sig = ci + cj;
 
   /* SPH acceleration term */

src/hydro/Minimal/hydro_io.h

@@ -102,10 +102,6 @@ __attribute__((always_inline)) INLINE static void hydro_write_particles(
  */
 void writeSPHflavour(hid_t h_grpsph) {
 
-  /* Kernel function description */
-  writeAttribute_s(h_grpsph, "Kernel", kernel_name);
-  writeAttribute_f(h_grpsph, "Hydro gamma", const_hydro_gamma);
-
   /* Viscosity and thermal conduction */
   /* Nothing in this minimal model... */
   writeAttribute_s(h_grpsph, "Thermal Conductivity Model", "No model");

src/hydro_properties.c

@@ -25,6 +25,8 @@
 #include <math.h>
 
 /* Local headers. */
+#include "adiabatic_index.h"
+#include "common_io.h"
 #include "error.h"
 #include "hydro.h"
 #include "kernel_hydro.h"
@@ -54,6 +56,7 @@ void hydro_props_init(struct hydro_props *p,
 
 void hydro_props_print(const struct hydro_props *p) {
 
+  message("Adiabatic index gamma: %f.", hydro_gamma);
   message("Hydrodynamic scheme: %s.", SPH_IMPLEMENTATION);
   message("Hydrodynamic kernel: %s with %.2f +/- %.2f neighbours (eta=%f).",
           kernel_name, p->target_neighbours, p->delta_neighbours,
@@ -68,3 +71,21 @@ void hydro_props_print(const struct hydro_props *p) {
     message("Maximal iterations in ghost task set to %d (default is %d)",
             p->max_smoothing_iterations, hydro_props_default_max_iterations);
 }
+
+#if defined(HAVE_HDF5)
+void hydro_props_print_snapshot(hid_t h_grpsph, const struct hydro_props *p) {
+
+  writeAttribute_f(h_grpsph, "Adiabatic index", hydro_gamma);
+  writeAttribute_s(h_grpsph, "Scheme", SPH_IMPLEMENTATION);
+  writeAttribute_s(h_grpsph, "Kernel function", kernel_name);
+  writeAttribute_f(h_grpsph, "Kernel target N_ngb", p->target_neighbours);
+  writeAttribute_f(h_grpsph, "Kernel delta N_ngb", p->delta_neighbours);
+  writeAttribute_f(h_grpsph, "Kernel eta", p->eta_neighbours);
+  writeAttribute_f(h_grpsph, "CFL parameter", p->CFL_condition);
+  writeAttribute_f(h_grpsph, "Volume log(max(delta h))", p->log_max_h_change);
+  writeAttribute_f(h_grpsph, "Volume max change time-step",
+                   powf(expf(p->log_max_h_change), 3.f));
+  writeAttribute_f(h_grpsph, "Max ghost iterations",
+                   p->max_smoothing_iterations);
+}
+#endif

src/hydro_properties.h

@@ -23,6 +23,10 @@
 /* Config parameters. */
 #include "../config.h"
 
+#if defined(HAVE_HDF5)
+#include <hdf5.h>
+#endif
+
 /* Local includes. */
 #include "const.h"
 #include "parser.h"
@@ -53,4 +57,8 @@ struct hydro_props {
 void hydro_props_print(const struct hydro_props *p);
 void hydro_props_init(struct hydro_props *p, const struct swift_params *params);
 
+#if defined(HAVE_HDF5)
+void hydro_props_print_snapshot(hid_t h_grpsph, const struct hydro_props *p);
+#endif
+
 #endif /* SWIFT_HYDRO_PROPERTIES */

src/parallel_io.c

@@ -39,7 +39,7 @@
 #include "common_io.h"
 #include "engine.h"
 #include "error.h"
-#include "kernel_hydro.h"
+#include "hydro_properties.h"
 #include "part.h"
 #include "units.h"
 
@@ -639,8 +639,10 @@ void write_output_parallel(struct engine* e, const char* baseName,
   writeCodeDescription(h_file);
 
   /* Print the SPH parameters */
-  h_grp = H5Gcreate(h_file, "/SPH", H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+  h_grp =
+      H5Gcreate(h_file, "/HydroScheme", H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
   if (h_grp < 0) error("Error while creating SPH group");
+  hydro_props_print_snapshot(h_grp, e->hydro_properties);
   writeSPHflavour(h_grp);
   H5Gclose(h_grp);
 

src/serial_io.c

@@ -39,7 +39,7 @@
 #include "common_io.h"
 #include "engine.h"
 #include "error.h"
-#include "kernel_hydro.h"
+#include "hydro_properties.h"
 #include "part.h"
 #include "units.h"
 
@@ -714,8 +714,10 @@ void write_output_serial(struct engine* e, const char* baseName,
     writeCodeDescription(h_file);
 
     /* Print the SPH parameters */
-    h_grp = H5Gcreate(h_file, "/SPH", H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+    h_grp = H5Gcreate(h_file, "/HydroScheme", H5P_DEFAULT, H5P_DEFAULT,
+                      H5P_DEFAULT);
     if (h_grp < 0) error("Error while creating SPH group");
+    hydro_props_print_snapshot(h_grp, e->hydro_properties);
     writeSPHflavour(h_grp);
     H5Gclose(h_grp);
 

src/single_io.c

@@ -38,7 +38,7 @@
 #include "common_io.h"
 #include "engine.h"
 #include "error.h"
-#include "kernel_hydro.h"
+#include "hydro_properties.h"
 #include "part.h"
 #include "units.h"
 
@@ -564,8 +564,10 @@ void write_output_single(struct engine* e, const char* baseName,
   writeCodeDescription(h_file);
 
   /* Print the SPH parameters */
-  h_grp = H5Gcreate(h_file, "/SPH", H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+  h_grp =
+      H5Gcreate(h_file, "/HydroScheme", H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
   if (h_grp < 0) error("Error while creating SPH group");
+  hydro_props_print_snapshot(h_grp, e->hydro_properties);
   writeSPHflavour(h_grp);
   H5Gclose(h_grp);
 

src/units.c

@@ -37,6 +37,7 @@
 #include "units.h"
 
 /* Includes. */
+#include "adiabatic_index.h"
 #include "const.h"
 #include "error.h"
 
@@ -188,14 +189,14 @@ void units_get_base_unit_exponants_array(float baseUnitsExp[5],
       break;
 
     case UNIT_CONV_ENTROPY:
-      baseUnitsExp[UNIT_MASS] = 1.f - const_hydro_gamma;
-      baseUnitsExp[UNIT_LENGTH] = 3.f * const_hydro_gamma - 1.f;
+      baseUnitsExp[UNIT_MASS] = 1.f - hydro_gamma;
+      baseUnitsExp[UNIT_LENGTH] = 3.f * hydro_gamma - 1.f;
       baseUnitsExp[UNIT_TIME] = -2.f;
       break;
 
     case UNIT_CONV_ENTROPY_PER_UNIT_MASS:
-      baseUnitsExp[UNIT_MASS] = -const_hydro_gamma;
-      baseUnitsExp[UNIT_LENGTH] = 3.f * const_hydro_gamma - 1.f;
+      baseUnitsExp[UNIT_MASS] = -hydro_gamma;
+      baseUnitsExp[UNIT_LENGTH] = 3.f * hydro_gamma - 1.f;
       baseUnitsExp[UNIT_TIME] = -2.f;
       break;