1 files changed, 88 insertions, 0 deletions
diff --git a/tests/test_matrix.c b/tests/test_matrix.c
new file mode 100644
index 00000000..a4a342aa
--- /dev/null
+++ b/tests/test_matrix.c
@@ -0,0 +1,88 @@
+/*
+ * Unit test for matrix-algebra code
+ *
+ * Check examples computed at
+ * http://www.elektro-energetika.cz/calculations/matreg.php
+ *
+ * This file is Copyright (c) 2010 by the GPSD project
+ * SPDX-License-Identifier: BSD-2-clause
+ */
+#include <stdlib.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <math.h>
+
+#include "../compiler.h"
+#include "../matrix.h"
+
+static struct {
+    double mat[4][4];
+    double inv[4][4];
+} inverses[] = {
+    /* identity matrix is self-inverse */
+    {
+	.mat = {{1,0,0,0}, {0,1,0,0}, {0,0,1,0}, {0,0,0,1}},
+	.inv = {{1,0,0,0}, {0,1,0,0}, {0,0,1,0}, {0,0,0,1}},
+    },
+    /* inverse of a diagonal matrix has reciprocal values */
+    {
+	.mat = {{10,0,0,0}, {0,10,0,0}, {0,0,10,0}, {0,0,0,10}},
+	.inv = {{0.1,0,0,0}, {0,0.1,0,0}, {0,0,0.1,0}, {0,0,0,0.1}},
+    },
+    /* random values with asymmetrical off-diagonal elements */
+    {
+	.mat = {{1,0,0,0}, {0,1,0,-2}, {0, 2,1,-4}, {0,0,0,1}},
+	.inv = {{1,0,0,0}, {0,1,0, 2}, {0,-2,1, 0}, {0,0,0,1}},
+    },
+    {
+	.mat = {{6,-4,1,-3},{-4,7,3,2},{1,3,6,-4},{-3,2,-4,6}},
+	.inv = {{14,34,-40,-31},{34,84,-99,-77},{-40,-99,117,91},{-31,-77,91,71}},
+    },
+};
+
+static void dump(const char *label, double m[4][4])
+{
+    printf("%s:\n", label);
+    printf("%f, %f, %f, %f\n", m[0][0], m[0][1], m[0][2], m[0][3]);
+    printf("%f, %f, %f, %f\n", m[1][0], m[1][1], m[1][2], m[1][3]);
+    printf("%f, %f, %f, %f\n", m[2][0], m[2][1], m[2][2], m[2][3]);
+    printf("%f, %f, %f, %f\n", m[3][0], m[3][1], m[3][2], m[3][3]);
+}
+
+static bool check_diag(int n, double a[4][4], double b[4][4])
+{
+#define approx(x, y)	(fabs(x - y) < 0.0001)
+
+    if (approx(b[0][0], a[0][0]) && approx(b[1][1], a[1][1]) &&
+	approx(b[2][2], a[2][2]) && approx(b[3][3], a[3][3]))
+	return true;
+
+    dump("a", a);
+    dump("b", b);
+    printf("Test %d residuals: %f %f %f %f\n",
+	   n,
+	   b[0][0] - a[0][0],
+	   b[1][1] - a[1][1],
+	   b[2][2] - a[2][2],
+	   b[3][3] - a[3][3]
+	);
+   return true;
+}
+
+int main(int argc UNUSED, char *argv[] UNUSED)
+{
+    unsigned int i;
+
+    for (i = 0; i < sizeof(inverses) / sizeof(inverses[0]); i++) {
+	double inverse[4][4];
+	if (!matrix_invert(inverses[i].mat, inverse)) {
+	    printf("Vanishing determinant in test %u\n", i);
+	}
+	if (!check_diag(i, inverse, inverses[i].inv))
+	    break;
+    }
+
+    printf("Matrix-algebra regression test succeeded\n");
+    exit(0);
+}