From ac68f70e20ed64bf13ae4910f8b4572731c67fee Mon Sep 17 00:00:00 2001
From: Axel Kohlmeyer <akohlmey@gmail.com>
Date: Thu, 9 Jan 2025 21:23:56 -0500
Subject: [PATCH] three more

---
 src/fix_nh.cpp       | 10 +++-------
 src/fix_recenter.cpp | 13 +++++--------
 src/fix_spring.cpp   | 10 +++-------
 3 files changed, 11 insertions(+), 22 deletions(-)

diff --git a/src/fix_nh.cpp b/src/fix_nh.cpp
index b56033d6d6..73f3908a6f 100644
--- a/src/fix_nh.cpp
+++ b/src/fix_nh.cpp
@@ -271,7 +271,7 @@ FixNH::FixNH(LAMMPS *lmp, int narg, char **arg) :
         delete[] id_dilate;
         id_dilate = utils::strdup(arg[iarg+1]);
         int idilate = group->find(id_dilate);
-        if (idilate == -1)
+        if (idilate < 0)
           error->all(FLERR,"Fix {} dilate group ID {} does not exist", style, id_dilate);
       }
       iarg += 2;
@@ -629,12 +629,8 @@ void FixNH::init()
 {
   // recheck that dilate group has not been deleted
 
-  if (allremap == 0) {
-    int idilate = group->find(id_dilate);
-    if (idilate == -1)
-      error->all(FLERR,"Fix {} dilate group ID {} does not exist", style, id_dilate);
-    dilate_group_bit = group->bitmask[idilate];
-  }
+  if (allremap == 0)
+    dilate_group_bit = group->get_bitmask_by_id(FLERR, id_dilate, fmt::format("fix {}", style));
 
   // ensure no conflict with fix deform
 
diff --git a/src/fix_recenter.cpp b/src/fix_recenter.cpp
index 4da8c4787b..2e9803870a 100644
--- a/src/fix_recenter.cpp
+++ b/src/fix_recenter.cpp
@@ -41,7 +41,7 @@ enum{BOX,LATTICE,FRACTION};
 FixRecenter::FixRecenter(LAMMPS *lmp, int narg, char **arg) :
   Fix(lmp, narg, arg)
 {
-  if (narg < 6) error->all(FLERR,"Illegal fix recenter command");
+  if (narg < 6) utils::missing_cmd_args(FLERR,"fix recenter", error);
 
   xcom = ycom = zcom = 0.0;
   xflag = yflag = zflag = 1;
@@ -74,17 +74,15 @@ FixRecenter::FixRecenter(LAMMPS *lmp, int narg, char **arg) :
   int iarg = 6;
   while (iarg < narg) {
     if (strcmp(arg[iarg],"shift") == 0) {
-      int igroup2 = group->find(arg[iarg+1]);
-      if (igroup2 < 0) error->all(FLERR,"Could not find fix recenter group ID");
-      group2bit = group->bitmask[igroup2];
+      group2bit = group->get_bitmask_by_id(FLERR, arg[iarg+1], "fix recenter");
       iarg += 2;
     } else if (strcmp(arg[iarg],"units") == 0) {
       if (strcmp(arg[iarg+1],"box") == 0) scaleflag = BOX;
       else if (strcmp(arg[iarg+1],"lattice") == 0) scaleflag = LATTICE;
       else if (strcmp(arg[iarg+1],"fraction") == 0) scaleflag = FRACTION;
-      else error->all(FLERR,"Illegal fix recenter command");
+      else error->all(FLERR,"Unknown fix recenter units argument {}", arg[iarg+1]);
       iarg += 2;
-    } else error->all(FLERR,"Illegal fix recenter command");
+    } else error->all(FLERR,"Unknown fix recenter keyword {}", arg[iarg]);
   }
 
   // scale xcom,ycom,zcom
@@ -103,8 +101,7 @@ FixRecenter::FixRecenter(LAMMPS *lmp, int narg, char **arg) :
 
   // cannot have 0 atoms in group
 
-  if (group->count(igroup) == 0)
-    error->all(FLERR,"Fix recenter group has no atoms");
+  if (group->count(igroup) == 0) error->all(FLERR,"Fix recenter group {} has no atoms", arg[1]);
 }
 
 /* ---------------------------------------------------------------------- */
diff --git a/src/fix_spring.cpp b/src/fix_spring.cpp
index 93c1f7867d..829073179d 100644
--- a/src/fix_spring.cpp
+++ b/src/fix_spring.cpp
@@ -73,11 +73,9 @@ FixSpring::FixSpring(LAMMPS *lmp, int narg, char **arg) :
 
     group2 = utils::strdup(arg[4]);
     igroup2 = group->find(arg[4]);
-    if (igroup2 == -1)
-      error->all(FLERR,"Fix spring couple group ID does not exist");
     if (igroup2 == igroup)
-      error->all(FLERR,"Two groups cannot be the same in fix spring couple");
-    group2bit = group->bitmask[igroup2];
+      error->all(FLERR,"The two groups cannot be the same in fix spring couple");
+    group2bit = group->get_bitmask_by_id(FLERR, arg[4], "fix spring");
 
     k_spring = utils::numeric(FLERR,arg[5],false,lmp);
     xflag = yflag = zflag = 1;
@@ -121,9 +119,7 @@ void FixSpring::init()
 
   if (group2) {
     igroup2 = group->find(group2);
-    if (igroup2 == -1)
-      error->all(FLERR,"Fix spring couple group ID does not exist");
-    group2bit = group->bitmask[igroup2];
+    group2bit = group->get_bitmask_by_id(FLERR, group2, "fix spring");
   }
 
   masstotal = group->mass(igroup);