From 6eda483e6747fd7758584846f470d36e7fc74b4d Mon Sep 17 00:00:00 2001
From: StuartBenjamin <stubenj9@mit.edu>
Date: Mon, 12 Oct 2026 22:47:22 -0700
Subject: [PATCH 1/2] RDCON - BUGFIX - MRE runs without a Zeff table use a flat
 Zeff, as before

With MRE_flag, a run whose rdcon.in has no psi_N_Zeff stopped ("Provide Zeff profile values"),
where develop used the scalar Zeff (default 1.52). One Zeff value, or none, without psi_N_Zeff
now gives a flat profile at that value, matching develop (mufrac to 1e-16 with Zeff = 2.0; 1e-9
with the default, which develop held in single precision). The profile spline's "extrap" end
condition needs 4 nodes, so shorter tables, which gave NaN, now stop with a message.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 rdcon/dcon.f    | 17 +++++++++++++++++
 rdcon/mercier.f | 12 ++++--------
 2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/rdcon/dcon.f b/rdcon/dcon.f
index ee948fbca..77d635e26 100644
--- a/rdcon/dcon.f
+++ b/rdcon/dcon.f
@@ -222,6 +222,7 @@ SUBROUTINE dcon_run
 
       LOGICAL :: cyl_flag=.FALSE.,regrid_flag=.FALSE.,verbose=.TRUE.
       INTEGER :: mmin,ipsi
+      REAL(r8) :: zeff0
       COMPLEX(r8), DIMENSION(:,:), ALLOCATABLE :: mx0
       COMPLEX(r8), DIMENSION(:), ALLOCATABLE :: vx0
 
@@ -346,6 +347,22 @@ SUBROUTINE dcon_run
       IF(MRE_flag)THEN
          CALL read_var_len(Zeff,Zeff_)
          CALL read_var_len(psi_N_Zeff,psi_N_Zeff_)
+c        one Zeff value (default 1.52) without psi_N_Zeff: flat profile.
+         IF(.NOT.ALLOCATED(psi_N_Zeff_))THEN
+            zeff0=1.52_r8
+            IF(ALLOCATED(Zeff_))THEN
+               IF(SIZE(Zeff_) > 1)
+     $              CALL program_stop("A Zeff profile needs psi_N_Zeff")
+               zeff0=Zeff_(1)
+               DEALLOCATE(Zeff_)
+            ENDIF
+            ALLOCATE(Zeff_(4),psi_N_Zeff_(4))
+            Zeff_=zeff0
+            psi_N_Zeff_=(/0.0_r8,1.0_r8/3,2.0_r8/3,1.0_r8/)
+         ENDIF
+         IF(.NOT.ALLOCATED(Zeff_) .OR. SIZE(Zeff_) /= SIZE(psi_N_Zeff_)
+     $     .OR. SIZE(Zeff_) < 4)
+     $     CALL program_stop("Zeff, psi_N_Zeff: equal sizes, >= 4")
          CALL spline_alloc(mreterms,mpsi,30)
          mreterms%xs=sq%xs
          mreterms%fs=0
diff --git a/rdcon/mercier.f b/rdcon/mercier.f
index b3e03ed23..277894db6 100644
--- a/rdcon/mercier.f
+++ b/rdcon/mercier.f
@@ -43,14 +43,10 @@ SUBROUTINE mercier_scan
 c-----------------------------------------------------------------------
       IF(MRE_flag)THEN
          CALL spline_alloc(ff,mtheta,22)
-         IF(ALLOCATED(Zeff_) .AND. ALLOCATED(psi_N_Zeff_))THEN
-            CALL spline_alloc(Zeff_spline,SIZE(psi_N_Zeff_)-1,1)
-            Zeff_spline%xs=psi_N_Zeff_
-            Zeff_spline%fs(:,1)=Zeff_
-            CALL spline_fit(Zeff_spline,"extrap")
-         ELSE
-            CALL program_stop("Provide Zeff profile values")
-         ENDIF
+         CALL spline_alloc(Zeff_spline,SIZE(psi_N_Zeff_)-1,1)
+         Zeff_spline%xs=psi_N_Zeff_
+         Zeff_spline%fs(:,1)=Zeff_
+         CALL spline_fit(Zeff_spline,"extrap")
       ELSE
          CALL spline_alloc(ff,mtheta,5)
       ENDIF

From a630b4855228ab369a41ab6c554d49053259f5dc Mon Sep 17 00:00:00 2001
From: Matthew Pharr <m.pharr@protonmail.com>
Date: Thu, 15 Oct 2026 12:25:04 +0200
Subject: [PATCH 2/2] RDCON - BUGFIX - make sure psi_N_Zeff is strictly
 increasing

---
 rdcon/dcon.f | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/rdcon/dcon.f b/rdcon/dcon.f
index 77d635e26..c4c9726bf 100644
--- a/rdcon/dcon.f
+++ b/rdcon/dcon.f
@@ -363,6 +363,8 @@ SUBROUTINE dcon_run
          IF(.NOT.ALLOCATED(Zeff_) .OR. SIZE(Zeff_) /= SIZE(psi_N_Zeff_)
      $     .OR. SIZE(Zeff_) < 4)
      $     CALL program_stop("Zeff, psi_N_Zeff: equal sizes, >= 4")
+         IF(ANY(psi_N_Zeff_(2:) <= psi_N_Zeff_(:SIZE(psi_N_Zeff_)-1)))
+     $     CALL program_stop("psi_N_Zeff must be strictly increasing")
          CALL spline_alloc(mreterms,mpsi,30)
          mreterms%xs=sq%xs
          mreterms%fs=0