Reference-LAPACK · rmlarsen · Sep 8, 2026 · Sep 8, 2026 · Sep 16, 2026
diff --git a/CMAKE/LAPACKTestHelpers.cmake b/CMAKE/LAPACKTestHelpers.cmake
@@ -44,17 +44,17 @@ function(lapack_no_constant_propagation_flag out_var)
   endif()
 endfunction()
 
-# Disable it for the ?errcxx drivers among ARGN, which manufacture their NaN
-# with SQRT( -ONE ).  Call this with every source list such a driver is built
-# from: the generated _64 and _TEST copies need it as much as the originals.
+# Disable it for the CXX error-exit and packed, banded and tridiagonal Cholesky tests among
+# ARGN, which manufacture NaNs. Call this with every source list: the
+# generated _64 and _TEST copies need it as much as the originals.
 function(lapack_nag_disable_constant_propagation)
   lapack_no_constant_propagation_flag(flag)
   if(NOT flag)
     return()
   endif()
   foreach(source IN LISTS ARGN)
     get_filename_component(name "${source}" NAME)
-    if(name MATCHES "^[scdz]errcxx(_[A-Za-z0-9]+)*\\.f$")
+    if(name MATCHES "^[scdz](errcxx|chkp[tpb])(_[A-Za-z0-9]+)*\\.f$")
       set_source_files_properties("${source}"
         PROPERTIES COMPILE_OPTIONS "${flag}")
     endif()

diff --git a/SRC/cpbtf2.f b/SRC/cpbtf2.f
@@ -163,8 +163,8 @@ SUBROUTINE CPBTF2( UPLO, N, KD, AB, LDAB, INFO )
       REAL               AJJ
 *     ..
 *     .. External Functions ..
-      LOGICAL            LSAME
-      EXTERNAL           LSAME
+      LOGICAL            LSAME, SISNAN
+      EXTERNAL           LSAME, SISNAN
 *     ..
 *     .. External Subroutines ..
       EXTERNAL           CHER, CLACGV, CSSCAL, XERBLA
@@ -208,7 +208,7 @@ SUBROUTINE CPBTF2( UPLO, N, KD, AB, LDAB, INFO )
 *           Compute U(J,J) and test for non-positive-definiteness.
 *
             AJJ = REAL( AB( KD+1, J ) )
-            IF( AJJ.LE.ZERO ) THEN
+            IF( AJJ.LE.ZERO.OR.SISNAN( AJJ ) ) THEN
                AB( KD+1, J ) = AJJ
                GO TO 30
             END IF
@@ -236,7 +236,7 @@ SUBROUTINE CPBTF2( UPLO, N, KD, AB, LDAB, INFO )
 *           Compute L(J,J) and test for non-positive-definiteness.
 *
             AJJ = REAL( AB( 1, J ) )
-            IF( AJJ.LE.ZERO ) THEN
+            IF( AJJ.LE.ZERO.OR.SISNAN( AJJ ) ) THEN
                AB( 1, J ) = AJJ
                GO TO 30
             END IF

diff --git a/SRC/cpptrf.f b/SRC/cpptrf.f
@@ -140,9 +140,9 @@ SUBROUTINE CPPTRF( UPLO, N, AP, INFO )
       REAL               AJJ
 *     ..
 *     .. External Functions ..
-      LOGICAL            LSAME
+      LOGICAL            LSAME, SISNAN
       COMPLEX            CDOTC
-      EXTERNAL           LSAME, CDOTC
+      EXTERNAL           LSAME, CDOTC, SISNAN
 *     ..
 *     .. External Subroutines ..
       EXTERNAL           CHPR, CSSCAL, CTPSV, XERBLA
@@ -191,7 +191,7 @@ SUBROUTINE CPPTRF( UPLO, N, AP, INFO )
 *
             AJJ = REAL( REAL( AP( JJ ) ) - CDOTC( J-1,
      $            AP( JC ), 1, AP( JC ), 1 ) )
-            IF( AJJ.LE.ZERO ) THEN
+            IF( AJJ.LE.ZERO.OR.SISNAN( AJJ ) ) THEN
                AP( JJ ) = AJJ
                GO TO 30
             END IF
@@ -207,7 +207,7 @@ SUBROUTINE CPPTRF( UPLO, N, AP, INFO )
 *           Compute L(J,J) and test for non-positive-definiteness.
 *
             AJJ = REAL( AP( JJ ) )
-            IF( AJJ.LE.ZERO ) THEN
+            IF( AJJ.LE.ZERO.OR.SISNAN( AJJ ) ) THEN
                AP( JJ ) = AJJ
                GO TO 30
             END IF

diff --git a/SRC/cpttrf.f b/SRC/cpttrf.f
@@ -111,6 +111,10 @@ SUBROUTINE CPTTRF( N, D, E, INFO )
       INTEGER            I, I4
       REAL               EII, EIR, F, G
 *     ..
+*     .. External Functions ..
+      LOGICAL            SISNAN
+      EXTERNAL           SISNAN
+*     ..
 *     .. External Subroutines ..
       EXTERNAL           XERBLA
 *     ..
@@ -137,7 +141,7 @@ SUBROUTINE CPTTRF( N, D, E, INFO )
 *
       I4 = MOD( N-1, 4 )
       DO 10 I = 1, I4
-         IF( D( I ).LE.ZERO ) THEN
+         IF( D( I ).LE.ZERO.OR.SISNAN( D( I ) ) ) THEN
             INFO = I
             GO TO 20
          END IF
@@ -154,7 +158,7 @@ SUBROUTINE CPTTRF( N, D, E, INFO )
 *        Drop out of the loop if d(i) <= 0: the matrix is not positive
 *        definite.
 *
-         IF( D( I ).LE.ZERO ) THEN
+         IF( D( I ).LE.ZERO.OR.SISNAN( D( I ) ) ) THEN
             INFO = I
             GO TO 20
          END IF
@@ -168,7 +172,7 @@ SUBROUTINE CPTTRF( N, D, E, INFO )
          E( I ) = CMPLX( F, G )
          D( I+1 ) = D( I+1 ) - F*EIR - G*EII
 *
-         IF( D( I+1 ).LE.ZERO ) THEN
+         IF( D( I+1 ).LE.ZERO.OR.SISNAN( D( I+1 ) ) ) THEN
             INFO = I+1
             GO TO 20
          END IF
@@ -182,7 +186,7 @@ SUBROUTINE CPTTRF( N, D, E, INFO )
          E( I+1 ) = CMPLX( F, G )
          D( I+2 ) = D( I+2 ) - F*EIR - G*EII
 *
-         IF( D( I+2 ).LE.ZERO ) THEN
+         IF( D( I+2 ).LE.ZERO.OR.SISNAN( D( I+2 ) ) ) THEN
             INFO = I+2
             GO TO 20
          END IF
@@ -196,7 +200,7 @@ SUBROUTINE CPTTRF( N, D, E, INFO )
          E( I+2 ) = CMPLX( F, G )
          D( I+3 ) = D( I+3 ) - F*EIR - G*EII
 *
-         IF( D( I+3 ).LE.ZERO ) THEN
+         IF( D( I+3 ).LE.ZERO.OR.SISNAN( D( I+3 ) ) ) THEN
             INFO = I+3
             GO TO 20
          END IF
@@ -213,7 +217,7 @@ SUBROUTINE CPTTRF( N, D, E, INFO )
 *
 *     Check d(n) for positive definiteness.
 *
-      IF( D( N ).LE.ZERO )
+      IF( D( N ).LE.ZERO.OR.SISNAN( D( N ) ) )
      $   INFO = N
 *
    20 CONTINUE

diff --git a/SRC/dpbtf2.f b/SRC/dpbtf2.f
@@ -163,8 +163,8 @@ SUBROUTINE DPBTF2( UPLO, N, KD, AB, LDAB, INFO )
       DOUBLE PRECISION   AJJ
 *     ..
 *     .. External Functions ..
-      LOGICAL            LSAME
-      EXTERNAL           LSAME
+      LOGICAL            LSAME, DISNAN
+      EXTERNAL           LSAME, DISNAN
 *     ..
 *     .. External Subroutines ..
       EXTERNAL           DSCAL, DSYR, XERBLA
@@ -208,7 +208,7 @@ SUBROUTINE DPBTF2( UPLO, N, KD, AB, LDAB, INFO )
 *           Compute U(J,J) and test for non-positive-definiteness.
 *
             AJJ = AB( KD+1, J )
-            IF( AJJ.LE.ZERO )
+            IF( AJJ.LE.ZERO.OR.DISNAN( AJJ ) )
      $         GO TO 30
             AJJ = SQRT( AJJ )
             AB( KD+1, J ) = AJJ
@@ -232,7 +232,7 @@ SUBROUTINE DPBTF2( UPLO, N, KD, AB, LDAB, INFO )
 *           Compute L(J,J) and test for non-positive-definiteness.
 *
             AJJ = AB( 1, J )
-            IF( AJJ.LE.ZERO )
+            IF( AJJ.LE.ZERO.OR.DISNAN( AJJ ) )
      $         GO TO 30
             AJJ = SQRT( AJJ )
             AB( 1, J ) = AJJ

diff --git a/SRC/dpptrf.f b/SRC/dpptrf.f
@@ -140,9 +140,9 @@ SUBROUTINE DPPTRF( UPLO, N, AP, INFO )
       DOUBLE PRECISION   AJJ
 *     ..
 *     .. External Functions ..
-      LOGICAL            LSAME
+      LOGICAL            LSAME, DISNAN
       DOUBLE PRECISION   DDOT
-      EXTERNAL           LSAME, DDOT
+      EXTERNAL           LSAME, DDOT, DISNAN
 *     ..
 *     .. External Subroutines ..
       EXTERNAL           DSCAL, DSPR, DTPSV, XERBLA
@@ -189,7 +189,7 @@ SUBROUTINE DPPTRF( UPLO, N, AP, INFO )
 *           Compute U(J,J) and test for non-positive-definiteness.
 *
             AJJ = AP( JJ ) - DDOT( J-1, AP( JC ), 1, AP( JC ), 1 )
-            IF( AJJ.LE.ZERO ) THEN
+            IF( AJJ.LE.ZERO.OR.DISNAN( AJJ ) ) THEN
                AP( JJ ) = AJJ
                GO TO 30
             END IF
@@ -205,7 +205,7 @@ SUBROUTINE DPPTRF( UPLO, N, AP, INFO )
 *           Compute L(J,J) and test for non-positive-definiteness.
 *
             AJJ = AP( JJ )
-            IF( AJJ.LE.ZERO ) THEN
+            IF( AJJ.LE.ZERO.OR.DISNAN( AJJ ) ) THEN
                AP( JJ ) = AJJ
                GO TO 30
             END IF

diff --git a/SRC/dpttrf.f b/SRC/dpttrf.f
@@ -109,6 +109,10 @@ SUBROUTINE DPTTRF( N, D, E, INFO )
       INTEGER            I, I4
       DOUBLE PRECISION   EI
 *     ..
+*     .. External Functions ..
+      LOGICAL            DISNAN
+      EXTERNAL           DISNAN
+*     ..
 *     .. External Subroutines ..
       EXTERNAL           XERBLA
 *     ..
@@ -135,7 +139,7 @@ SUBROUTINE DPTTRF( N, D, E, INFO )
 *
       I4 = MOD( N-1, 4 )
       DO 10 I = 1, I4
-         IF( D( I ).LE.ZERO ) THEN
+         IF( D( I ).LE.ZERO.OR.DISNAN( D( I ) ) ) THEN
             INFO = I
             GO TO 30
          END IF
@@ -149,7 +153,7 @@ SUBROUTINE DPTTRF( N, D, E, INFO )
 *        Drop out of the loop if d(i) <= 0: the matrix is not positive
 *        definite.
 *
-         IF( D( I ).LE.ZERO ) THEN
+         IF( D( I ).LE.ZERO.OR.DISNAN( D( I ) ) ) THEN
             INFO = I
             GO TO 30
          END IF
@@ -160,7 +164,7 @@ SUBROUTINE DPTTRF( N, D, E, INFO )
          E( I ) = EI / D( I )
          D( I+1 ) = D( I+1 ) - E( I )*EI
 *
-         IF( D( I+1 ).LE.ZERO ) THEN
+         IF( D( I+1 ).LE.ZERO.OR.DISNAN( D( I+1 ) ) ) THEN
             INFO = I + 1
             GO TO 30
          END IF
@@ -171,7 +175,7 @@ SUBROUTINE DPTTRF( N, D, E, INFO )
          E( I+1 ) = EI / D( I+1 )
          D( I+2 ) = D( I+2 ) - E( I+1 )*EI
 *
-         IF( D( I+2 ).LE.ZERO ) THEN
+         IF( D( I+2 ).LE.ZERO.OR.DISNAN( D( I+2 ) ) ) THEN
             INFO = I + 2
             GO TO 30
          END IF
@@ -182,7 +186,7 @@ SUBROUTINE DPTTRF( N, D, E, INFO )
          E( I+2 ) = EI / D( I+2 )
          D( I+3 ) = D( I+3 ) - E( I+2 )*EI
 *
-         IF( D( I+3 ).LE.ZERO ) THEN
+         IF( D( I+3 ).LE.ZERO.OR.DISNAN( D( I+3 ) ) ) THEN
             INFO = I + 3
             GO TO 30
          END IF
@@ -196,7 +200,7 @@ SUBROUTINE DPTTRF( N, D, E, INFO )
 *
 *     Check d(n) for positive definiteness.
 *
-      IF( D( N ).LE.ZERO )
+      IF( D( N ).LE.ZERO.OR.DISNAN( D( N ) ) )
      $   INFO = N
 *
    30 CONTINUE

diff --git a/SRC/spbtf2.f b/SRC/spbtf2.f
@@ -163,8 +163,8 @@ SUBROUTINE SPBTF2( UPLO, N, KD, AB, LDAB, INFO )
       REAL               AJJ
 *     ..
 *     .. External Functions ..
-      LOGICAL            LSAME
-      EXTERNAL           LSAME
+      LOGICAL            LSAME, SISNAN
+      EXTERNAL           LSAME, SISNAN
 *     ..
 *     .. External Subroutines ..
       EXTERNAL           SSCAL, SSYR, XERBLA
@@ -208,7 +208,7 @@ SUBROUTINE SPBTF2( UPLO, N, KD, AB, LDAB, INFO )
 *           Compute U(J,J) and test for non-positive-definiteness.
 *
             AJJ = AB( KD+1, J )
-            IF( AJJ.LE.ZERO )
+            IF( AJJ.LE.ZERO.OR.SISNAN( AJJ ) )
      $         GO TO 30
             AJJ = SQRT( AJJ )
             AB( KD+1, J ) = AJJ
@@ -232,7 +232,7 @@ SUBROUTINE SPBTF2( UPLO, N, KD, AB, LDAB, INFO )
 *           Compute L(J,J) and test for non-positive-definiteness.
 *
             AJJ = AB( 1, J )
-            IF( AJJ.LE.ZERO )
+            IF( AJJ.LE.ZERO.OR.SISNAN( AJJ ) )
      $         GO TO 30
             AJJ = SQRT( AJJ )
             AB( 1, J ) = AJJ

diff --git a/SRC/spptrf.f b/SRC/spptrf.f
@@ -140,9 +140,9 @@ SUBROUTINE SPPTRF( UPLO, N, AP, INFO )
       REAL               AJJ
 *     ..
 *     .. External Functions ..
-      LOGICAL            LSAME
+      LOGICAL            LSAME, SISNAN
       REAL               SDOT
-      EXTERNAL           LSAME, SDOT
+      EXTERNAL           LSAME, SDOT, SISNAN
 *     ..
 *     .. External Subroutines ..
       EXTERNAL           SSCAL, SSPR, STPSV, XERBLA
@@ -189,7 +189,7 @@ SUBROUTINE SPPTRF( UPLO, N, AP, INFO )
 *           Compute U(J,J) and test for non-positive-definiteness.
 *
             AJJ = AP( JJ ) - SDOT( J-1, AP( JC ), 1, AP( JC ), 1 )
-            IF( AJJ.LE.ZERO ) THEN
+            IF( AJJ.LE.ZERO.OR.SISNAN( AJJ ) ) THEN
                AP( JJ ) = AJJ
                GO TO 30
             END IF
@@ -205,7 +205,7 @@ SUBROUTINE SPPTRF( UPLO, N, AP, INFO )
 *           Compute L(J,J) and test for non-positive-definiteness.
 *
             AJJ = AP( JJ )
-            IF( AJJ.LE.ZERO ) THEN
+            IF( AJJ.LE.ZERO.OR.SISNAN( AJJ ) ) THEN
                AP( JJ ) = AJJ
                GO TO 30
             END IF

diff --git a/SRC/spttrf.f b/SRC/spttrf.f
@@ -109,6 +109,10 @@ SUBROUTINE SPTTRF( N, D, E, INFO )
       INTEGER            I, I4
       REAL               EI
 *     ..
+*     .. External Functions ..
+      LOGICAL            SISNAN
+      EXTERNAL           SISNAN
+*     ..
 *     .. External Subroutines ..
       EXTERNAL           XERBLA
 *     ..
@@ -135,7 +139,7 @@ SUBROUTINE SPTTRF( N, D, E, INFO )
 *
       I4 = MOD( N-1, 4 )
       DO 10 I = 1, I4
-         IF( D( I ).LE.ZERO ) THEN
+         IF( D( I ).LE.ZERO.OR.SISNAN( D( I ) ) ) THEN
             INFO = I
             GO TO 30
          END IF
@@ -149,7 +153,7 @@ SUBROUTINE SPTTRF( N, D, E, INFO )
 *        Drop out of the loop if d(i) <= 0: the matrix is not positive
 *        definite.
 *
-         IF( D( I ).LE.ZERO ) THEN
+         IF( D( I ).LE.ZERO.OR.SISNAN( D( I ) ) ) THEN
             INFO = I
             GO TO 30
          END IF
@@ -160,7 +164,7 @@ SUBROUTINE SPTTRF( N, D, E, INFO )
          E( I ) = EI / D( I )
          D( I+1 ) = D( I+1 ) - E( I )*EI
 *
-         IF( D( I+1 ).LE.ZERO ) THEN
+         IF( D( I+1 ).LE.ZERO.OR.SISNAN( D( I+1 ) ) ) THEN
             INFO = I + 1
             GO TO 30
          END IF
@@ -171,7 +175,7 @@ SUBROUTINE SPTTRF( N, D, E, INFO )
          E( I+1 ) = EI / D( I+1 )
          D( I+2 ) = D( I+2 ) - E( I+1 )*EI
 *
-         IF( D( I+2 ).LE.ZERO ) THEN
+         IF( D( I+2 ).LE.ZERO.OR.SISNAN( D( I+2 ) ) ) THEN
             INFO = I + 2
             GO TO 30
          END IF
@@ -182,7 +186,7 @@ SUBROUTINE SPTTRF( N, D, E, INFO )
          E( I+2 ) = EI / D( I+2 )
          D( I+3 ) = D( I+3 ) - E( I+2 )*EI
 *
-         IF( D( I+3 ).LE.ZERO ) THEN
+         IF( D( I+3 ).LE.ZERO.OR.SISNAN( D( I+3 ) ) ) THEN
             INFO = I + 3
             GO TO 30
          END IF
@@ -196,7 +200,7 @@ SUBROUTINE SPTTRF( N, D, E, INFO )
 *
 *     Check d(n) for positive definiteness.
 *
-      IF( D( N ).LE.ZERO )
+      IF( D( N ).LE.ZERO.OR.SISNAN( D( N ) ) )
      $   INFO = N
 *
    30 CONTINUE