matrix: Avoid gsl_linalg_LU_invx() because it was new in GSL 2.6.

Debian only added GSL 2.6 in the current stable (bullseye) but one of the
CI systems is using oldstable (buster), thus failures.

Thanks to Friedrich Beckmann for reporting the problem.

diff --git a/src/language/stats/matrix.c b/src/language/stats/matrix.c
index 64d8dd92f83873465a0727415c1604c3843a452c..8a08740183a54f72dba21798abae29d9fa42d6c1 100644 (file)
--- a/src/language/stats/matrix.c
+++ b/src/language/stats/matrix.c
@@ -1851,21 +1851,24 @@ matrix_eval_IDENT (double s1, double s2)
   return m;
 }
 
+/* Inverts X, storing the inverse into INVERSE.  As a side effect, replaces X
+   by its LU decomposition. */
 static void
-invert_matrix (gsl_matrix *x)
+invert_matrix (gsl_matrix *x, gsl_matrix *inverse)
 {
   gsl_permutation *p = gsl_permutation_alloc (x->size1);
   int signum;
   gsl_linalg_LU_decomp (x, p, &signum);
-  gsl_linalg_LU_invx (x, p);
+  gsl_linalg_LU_invert (x, p, inverse);
   gsl_permutation_free (p);
 }
 
 static gsl_matrix *
-matrix_eval_INV (gsl_matrix *m)
+matrix_eval_INV (gsl_matrix *src)
 {
-  invert_matrix (m);
-  return m;
+  gsl_matrix *dst = gsl_matrix_alloc (src->size1, src->size2);
+  invert_matrix (src, dst);
+  return dst;
 }
 
 static gsl_matrix *
@@ -3405,7 +3408,10 @@ matrix_expr_evaluate_exp_mat (const struct matrix_expr *e,
 
   mul_matrix (&y, x, y, &t);
   if (bf < 0)
-    invert_matrix (y);
+    {
+      invert_matrix (y, x);
+      swap_matrix (&x, &y);
+    }
 
   /* Garbage collection.