From 432129dc60b0eb61d2a6524974134477c50e5140 Mon Sep 17 00:00:00 2001
From: Joshua Kammeraad <joshkamm@umich.edu>
Date: Thu, 19 Feb 2026 06:03:39 -0500
Subject: [PATCH] Fix CUDA crash in GTO compute_rho when density gradients not
 needed

Add missing `if (need_grad)` guards before two val1g/val2g zero-initialization
loops in the single-precision GTO `compute_rho()`. When called without density
gradients (drho=NULL, e.g. HF), these arrays are NULL, causing
CUDA_ERROR_ILLEGAL_ADDRESS on the GPU. Matches the pattern already used in
the double-precision `compute_rhodg()`.

Fixes ZimmermanGroup/ZEST#62

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 src/integrals/becke.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/integrals/becke.cpp b/src/integrals/becke.cpp
index 5485dd8..fc05cbb 100644
--- a/src/integrals/becke.cpp
+++ b/src/integrals/becke.cpp
@@ -1971,6 +1971,7 @@ void compute_rho(bool gbasis, int natoms, int* atno, double* coords, vector<vect
     for (int j=0;j<gsa;j++)
       val1[i1][j] = 0.f;
 
+    if (need_grad)
     #pragma acc parallel loop collapse(2) present(val1g[0:iN][0:gsa3])
     for (int i1=0;i1<s2-s1;i1++)
     for (int j=0;j<gsa3;j++)
@@ -2052,6 +2053,7 @@ void compute_rho(bool gbasis, int natoms, int* atno, double* coords, vector<vect
       for (int j=0;j<gsa;j++)
         val2[i2][j] = 0.f;
 
+      if (need_grad)
       #pragma acc parallel loop collapse(2) present(val2g[0:iN][0:gsa3])
       for (int i2=0;i2<s4-s3;i2++)
       for (int j=0;j<gsa3;j++)