From 66d042a0ee3e78b43d933a616ccd020d42a14701 Mon Sep 17 00:00:00 2001
From: Steve Plimpton <sjplimp@gmail.com>
Date: Thu, 4 Apr 2024 14:11:13 -0600
Subject: [PATCH] make checks for exceeding length of variable-length vectors
 more consistent

---
 src/EXTRA-FIX/fix_ave_correlate_long.cpp |  4 +++-
 src/fix_ave_correlate.cpp                |  6 ++++--
 src/fix_ave_histo.cpp                    |  6 ++++--
 src/fix_ave_time.cpp                     |  5 +++--
 src/thermo.cpp                           | 10 ++++++++--
 5 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/src/EXTRA-FIX/fix_ave_correlate_long.cpp b/src/EXTRA-FIX/fix_ave_correlate_long.cpp
index fc1760b353..7c80365c57 100644
--- a/src/EXTRA-FIX/fix_ave_correlate_long.cpp
+++ b/src/EXTRA-FIX/fix_ave_correlate_long.cpp
@@ -454,6 +454,8 @@ void FixAveCorrelateLong::end_of_step()
         scalar = val.val.f->compute_vector(val.argindex-1);
 
     // evaluate equal-style or vector-style variable
+    // if index exceeds vector length, use a zero value
+    //   this can be useful if vector length is not known a priori
 
     } else if (val.which == ArgInfo::VARIABLE) {
       if (val.argindex == 0)
@@ -462,7 +464,7 @@ void FixAveCorrelateLong::end_of_step()
         double *varvec;
         int nvec = input->variable->compute_vector(val.val.v,&varvec);
         int index = val.argindex;
-        if (nvec < index) scalar = 0.0;
+        if (index > nvec) scalar = 0.0;
         else scalar = varvec[index-1];
       }
     }
diff --git a/src/fix_ave_correlate.cpp b/src/fix_ave_correlate.cpp
index 4b9e316b9d..576ddb3c94 100644
--- a/src/fix_ave_correlate.cpp
+++ b/src/fix_ave_correlate.cpp
@@ -414,7 +414,9 @@ void FixAveCorrelate::end_of_step()
         scalar = val.val.f->compute_vector(val.argindex-1);
 
     // evaluate equal-style or vector-style variable
-
+    // if index exceeds vector length, use a zero value
+    //   this can be useful if vector length is not known a priori
+      
     } else if (val.which == ArgInfo::VARIABLE) {
       if (val.argindex == 0)
         scalar = input->variable->compute_equal(val.val.v);
@@ -422,7 +424,7 @@ void FixAveCorrelate::end_of_step()
         double *varvec;
         int nvec = input->variable->compute_vector(val.val.v,&varvec);
         int index = val.argindex;
-        if (nvec < index) scalar = 0.0;
+        if (index > nvec) scalar = 0.0;
         else scalar = varvec[index-1];
       }
     }
diff --git a/src/fix_ave_histo.cpp b/src/fix_ave_histo.cpp
index b3ca9e1106..44e64c4d5a 100644
--- a/src/fix_ave_histo.cpp
+++ b/src/fix_ave_histo.cpp
@@ -600,6 +600,8 @@ void FixAveHisto::end_of_step()
       }
 
     // evaluate equal-style or vector-style or atom-style variable
+    // if index exceeds vector length, use a zero value
+    //   this can be useful if vector length is not known a priori
 
     } else if (val.which == ArgInfo::VARIABLE) {
       if (kind == GLOBAL && mode == SCALAR) {
@@ -607,7 +609,7 @@ void FixAveHisto::end_of_step()
         else {
           double *varvec;
           int nvec = input->variable->compute_vector(val.val.v,&varvec);
-          if (nvec < j) bin_one(0.0);
+          if (j > nvec) bin_one(0.0);
           else bin_one(varvec[j-1]);
         }
 
@@ -637,7 +639,7 @@ void FixAveHisto::end_of_step()
     modify->addstep_compute(nvalid);
     return;
   }
-
+  
   irepeat = 0;
   nvalid = ntimestep + nfreq - static_cast<bigint>(nrepeat-1)*nevery;
   modify->addstep_compute(nvalid);
diff --git a/src/fix_ave_time.cpp b/src/fix_ave_time.cpp
index c88d8e1659..417e0fd97a 100644
--- a/src/fix_ave_time.cpp
+++ b/src/fix_ave_time.cpp
@@ -562,7 +562,8 @@ void FixAveTime::invoke_scalar(bigint ntimestep)
         scalar = val.val.f->compute_vector(val.argindex-1);
 
     // evaluate equal-style or vector-style variable
-    // ensure no out-of-range access to vector-style variable
+    // if index exceeds vector length, use a zero value
+    //   this can be useful if vector length is not known a priori
 
     } else if (val.which == ArgInfo::VARIABLE) {
       if (val.argindex == 0)
@@ -570,7 +571,7 @@ void FixAveTime::invoke_scalar(bigint ntimestep)
       else {
         double *varvec;
         int nvec = input->variable->compute_vector(val.val.v,&varvec);
-        if (nvec < val.argindex) scalar = 0.0;
+        if (val.argindex > nvec) scalar = 0.0;
         else scalar = varvec[val.argindex-1];
       }
     }
diff --git a/src/thermo.cpp b/src/thermo.cpp
index dbb8b2530e..5ef5eb59b8 100644
--- a/src/thermo.cpp
+++ b/src/thermo.cpp
@@ -1515,6 +1515,8 @@ void Thermo::compute_fix()
   int m = field2index[ifield];
   Fix *fix = fixes[m];
 
+  // check for out-of-range access if vector/array is variable length
+
   if (argindex1[ifield] == 0) {
     dvalue = fix->compute_scalar();
     if (normflag && fix->extscalar) dvalue /= natoms;
@@ -1544,13 +1546,17 @@ void Thermo::compute_variable()
 {
   int iarg = argindex1[ifield];
 
+  // evaluate equal-style or vector-style variable
+  // if index exceeds vector length, use a zero value
+  //   this can be useful if vector length is not known a priori
+
   if (iarg == 0)
     dvalue = input->variable->compute_equal(variables[field2index[ifield]]);
   else {
     double *varvec;
     int nvec = input->variable->compute_vector(variables[field2index[ifield]], &varvec);
-    if (iarg > nvec) error->all(FLERR, "Thermo vector-style variable is accessed out-of-range");
-    dvalue = varvec[iarg - 1];
+    if (iarg > nvec) dvalue = 0.0;
+    else dvalue = varvec[iarg - 1];
   }
 }