PyREC scaffolding (from YREC development, 7be4133)/ gtpurz.fGlossary

gtpurz.f

135 lines · 1 definitions · on GitHub (7be4133)

Python version: gtpurz.py, 122 lines, on the right (switch to Python above the code).

Variables on this page (8)

ishort, numrsz, numtz, tollaol, zot, zsdorl, zslaoll, zsrhol

Purpose

GTPURZ returns the opacity from the LAOL89 table for pure metals ($Z = 1$), with its derivatives, at a given density and temperature.

How it fits

Called only by GETOPAC, when $Z > 0.1$ and $\log T > 7.0$ (getopac.f, line 109↗, lowered from 7.7 by "JCZ 211125"; its error message still says "Z>0.10 T > 5 X 10^7 K"; it stops if no pure-$Z$ table was read, LPUREZ): GETOPAC then interpolates $\log\kappa$ and its derivatives linearly in $Z$ between a normal table (at ZIT) and this pure-$Z$ table ($Z = 1$). The table is in the modules ZLAOL_MOD (read by RDZLAOL) and ZSLAOL_MOD (its density splines, from ZSULAOL), COMMON blocks until rp_1; it takes TOLLAOL from NMLPAR_MOD (formerly /NWLAOL/) and the output unit from IOUNITS_MOD. Calls LOCATE, XRNG4, CSPLINE, SPLINT.

The method

As in GTLAOL (removed since rp_1) but without the composition step: a spline in $\log\rho$ at each of four temperatures (with linear extrapolation within the margin $\ln$ TOLLAOL, a natural log where the densities are base 10: suspected bug 2), then a natural spline in $\log T$; chord slopes for the derivatives; $\log\kappa$ capped at 35.

Suspected bugs, checked by running the code

Each bug is marked by what running the code showed: (changes results, large) or (small), the fix moving a run clearly beyond a null change; (stops the run); (wrong output), the fix changing only what is written; (harmless in the runs), within the noise; (never occurred), the code ran but the fault did not; (not reached); (cannot be reached), a guard prevents it; (withdrawn), the suspicion was wrong.

1. (not reached) A density beyond the table's margin is reported as a temperature.

(lines 81–105↗, lines 120–126↗) At each of the four temperatures XRNG4 picks, a density inside the table or within TOLLOG of its edges adds a point; one beyond the margin adds none, silently. With one point missing, NUMTS < 4 and the run stops with "OUTSIDE Z OPACITY TABLE, IN TEMPERATURE," though the cause is the density. Only with the pure-metal table in use (LPUREZ, in helium-burning cores with $Z > 0.1$ above $\log T = 7.0$, getopac.f, lines 109–116↗).

A possible fix:

gtpurz.f

@@ lines 103–108 @@
                TT(NUMTS) = ZOT(IT)
                DODR(NUMTS) = SLOPE
             END IF
+C 11/09/26 KC via Claude
+C code changed to name the density when it lies beyond the table's
+C margin at one of the four temperatures.
+            IF(NUMTS.LT.IT-JT1+1) THEN
+               WRITE(ISHORT,120)DL,TL
+               STOP 1
+            END IF
          ELSE
             WRITE(ISHORT,120)DL,TL
   120       FORMAT(' OUTSIDE Z OPACITY TABLE, IN DENSITY.  ',

Checked by running YREC (Nov 9, 2026; a line added at each suspected path counted how often it was taken, the outputs otherwise unchanged): not reached in any of 34 runs, 26 of YREC's cases (from a 0.04 $M_\odot$ brown dwarf and the solar models to 9 $M_\odot$, rotation, and helium burning) and 8 made-up ones (each one of YREC's cases with a few settings changed), of which one stopped in its first second: No run stopped here. What would reach it: a density beyond the table's margin at one of the four temperatures. The fix only changes a message, so it was not run. Intent: none found.

2. (never occurred) The extrapolation margin is a natural log.

(line 66↗; line 87↗; lines 95–96↗) TOLLOG = LOG(TOLLAOL) is the natural log of TOLLAOL, while it is compared with base-10 densities (TR, from ZSRHOL, which ZSULAOL fills with LOG10(ZORHO(IR)), zsulaol.f, line 35↗, zsulaol.f, line 43↗): With the default TOLLAOL = 10, which no case sets and YREC's documentation does not describe, a density up to 2.30 dex beyond the table's edge is extrapolated linearly, silently, rather than up to 1 dex. Only with the pure-metal table in use (LPUREZ, in helium-burning cores with $Z > 0.1$ above $\log T = 7.0$, getopac.f, lines 109–116↗) and a density 1 to 2.30 dex beyond the table's edge (in PURECO.DBGLAOL, the test suite's table, the densest entries of the temperatures near $\log T = 8$ end between $2 \times 10^5$ and $3 \times 10^6$ g/cm³); beyond the margin the run stops.

A possible fix:

gtpurz.f

@@ lines 63–69 @@
 C     IF WITHIN TOLLAOL OF EDGE THEN LINEAR EXTRAPOLATE
 C
 C     TOLLAOL PERMITS SOME EXTRAPLOATION BEYOND TABLE EDGE.
-      TOLLOG = LOG(TOLLAOL)
+C 11/10/26 KC via Claude
+C code changed to take the margin in decades, as the log10 densities
+C it is compared with.
+      TOLLOG = LOG10(TOLLAOL)
       RTL = TL
       RDL = DL
       CALL LOCATE(ZOT,NUMTZ,RTL,JT)

Checked by running YREC (Nov 10, 2026; a line added at each suspected path counted how often it was taken, the outputs otherwise unchanged): The density test ran 57,404,252 times (once at each of the four table temperatures of every call) in testsuite/Test_m0p95feh+0p0_GN93_TAHB and 53,733,784 times in testsuite/Test_m9p0feh+0p0GS98_base_TAHB, and the density stayed at least 0.48 dex inside the table's upper edge and at least 9.02 dex above its lower edge every time, so neither margin was used. What would reach it: a helium-burning core denser than the table's top by more than 1 dex (not run). The fix was not run, since there was nothing to compare. Intent: none found; the comment (lines 63–65↗, "TOLLAOL PERMITS SOME EXTRAPLOATION BEYOND TABLE EDGE.") does not say whether TOLLAOL is a factor in density.

Definitions

subroutineGTPURZ

lines 6–135 · GitHub

Opacity of a pure-metal mixture: spline in $\rho$, then in $T$.

Uses modules IOUNITS_MOD, NMLPAR_MOD, ZLAOL_MOD, ZSLAOL_MOD

Called by GETOPAC

Flowchart of its calls, in order (5)
LOCATE69→XRNG472
for IT=JT1, JT2, lines 73–113
if (NUMS .GE. 4), lines 75–105
if (RDL.GT.TR(1) .AND. RDL.LT.TR(NUMS)), lines 81–86
SPLINT82
if (NUMTS .GE. 4), lines 114–119
CSPLINE115→SPLINT116

Change log

The changes since rp_1

Changed since rp_1. Declarations only: COMMON blocks to modules, IMPLICIT NONE, the local TOLL renamed TOLLOG, and the unused /SLAOL/ no longer declared (question 1 of rp_1, now settled and removed).

Changed since a8a5950. The two stops for a point outside the table (in density, in temperature) now exit with status 1, the code for run-time errors, instead of a bare STOP (KNOWN_ISSUES.md, issue 38).