From 3f96629c4925cbcf446bfbff3e160ac9e1eab992 Mon Sep 17 00:00:00 2001
From: John ZuHone <jzuhone@gmail.com>
Date: Wed, 15 Nov 2023 11:24:17 -0500
Subject: [PATCH] Fix problems with EOS detection

---
 yt/frontends/gamer/cfields.pyx | 16 ++++++++--------
 yt/frontends/gamer/fields.py   |  8 +++++---
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/yt/frontends/gamer/cfields.pyx b/yt/frontends/gamer/cfields.pyx
index 76eb5c75d4a..dcdab90c0fd 100644
--- a/yt/frontends/gamer/cfields.pyx
+++ b/yt/frontends/gamer/cfields.pyx
@@ -7,7 +7,7 @@ cimport numpy as np
 import numpy as np
 
 
-cdef np.float64_t h_eos4(np.float64_t kT, np.float64_t g) noexcept nogil:
+cdef np.float64_t h_eos_tb(np.float64_t kT, np.float64_t g) noexcept nogil:
     cdef np.float64_t x
     x = 2.25 * kT * kT
     return 2.5 * kT + x / (1.0 + math.sqrt(x + 1.0))
@@ -18,14 +18,14 @@ cdef np.float64_t h_eos(np.float64_t kT, np.float64_t g) noexcept nogil:
 cdef np.float64_t gamma_eos(np.float64_t kT, np.float64_t g) noexcept nogil:
     return g
 
-cdef np.float64_t gamma_eos4(np.float64_t kT, np.float64_t g) noexcept nogil:
+cdef np.float64_t gamma_eos_tb(np.float64_t kT, np.float64_t g) noexcept nogil:
     cdef np.float64_t x, c_p, c_v
     x = 2.25 * kT / math.sqrt(2.25 * kT * kT + 1.0)
     c_p = 2.5 + x
     c_v = 1.5 + x
     return c_p / c_v
 
-cdef np.float64_t cs_eos4(np.float64_t kT, np.float64_t c, np.float64_t g) noexcept nogil:
+cdef np.float64_t cs_eos_tb(np.float64_t kT, np.float64_t c, np.float64_t g) noexcept nogil:
     cdef np.float64_t hp, cs2
     hp = h_eos4(kT, 0.0) + 1.0
     cs2 = kT / (3.0 * hp)
@@ -52,14 +52,14 @@ cdef class SRHDFields:
         self._c = clight
         self._c2 = clight * clight
         # Select aux functions based on eos no.
-        if (eos == 4):
-            self.h = h_eos4
-            self.gamma = gamma_eos4
-            self.cs = cs_eos4
-        else:
+        if eos == 1:
             self.h = h_eos
             self.gamma = gamma_eos
             self.cs = cs_eos
+        else:
+            self.h = h_eos_tb
+            self.gamma = gamma_eos_tb
+            self.cs = cs_eos_tb
 
     cdef np.float64_t _lorentz_factor(
             self,
diff --git a/yt/frontends/gamer/fields.py b/yt/frontends/gamer/fields.py
index fe182886ceb..b5e4ac4a06b 100644
--- a/yt/frontends/gamer/fields.py
+++ b/yt/frontends/gamer/fields.py
@@ -62,10 +62,12 @@ def setup_fluid_fields(self):
         if self.ds.srhd:
             c2 = pc.clight * pc.clight
             c = pc.clight.in_units("code_length / code_time")
-            if self.ds.eos == 4:
-                fgen = SRHDFields(self.ds.eos, 0.0, c.d)
-            else:
+            if self.ds.eos == 1:
+                # gamma-law EOS
                 fgen = SRHDFields(self.ds.eos, self.ds.gamma, c.d)
+            else:
+                # Taub-Mathews EOS
+                fgen = SRHDFields(self.ds.eos, 0.0, c.d)
 
             def _sound_speed(field, data):
                 out = fgen.sound_speed(data["gamer", "Temp"].d)