From 650c4400c63d8ec8473321862046240cb873ec8d Mon Sep 17 00:00:00 2001
From: pacien
Date: Sat, 2 Dec 2017 01:10:02 +0100
Subject: Add matrix op impl. and test, minor spec change

Signed-off-by: pacien <pacien.trangirard@pacien.net>
---
 src/common/matrix.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 src/common/matrix.c

(limited to 'src/common')

diff --git a/src/common/matrix.c b/src/common/matrix.c
new file mode 100644
index 0000000..60f9afb
--- /dev/null
+++ b/src/common/matrix.c
@@ -0,0 +1,63 @@
+#include "common/matrix.h"
+#include <assert.h>
+#include <memory.h>
+#include <stdlib.h>
+#include "common/mem.h"
+
+static inline IntSquareMatrix *matrix_without_row(IntSquareMatrix *target, IntSquareMatrix *origin,
+                                                  IntVector omitted_row) {
+  int origin_row, target_row;
+
+  for (origin_row = 0, target_row = 0; origin_row < origin->dim; ++origin_row)
+    if (origin_row != omitted_row)
+      target->elements[target_row++] = origin->elements[origin_row];
+
+  return target;
+}
+
+static inline IntVector det_dev_sign(IntVector row, IntVector col) {
+  assert(row > 0 && col > 0);
+  return ((row + col) % 2 == 0) ? 1 : -1;
+}
+
+static inline IntVector det_reduce(IntSquareMatrix *matrix) {
+  IntSquareMatrix sub_matrix;
+  int row;
+  IntVector det = 0;
+
+  assert(matrix->dim > 2);
+
+  sub_matrix.dim = matrix->dim - 1;
+  sub_matrix.elements = malloc_or_die(sub_matrix.dim * sizeof(IntVector *));
+
+  for (row = 0; row < matrix->dim; ++row)
+    det += matrix->elements[row][matrix->dim - 1]
+           * det_dev_sign(row + 1, matrix->dim)
+           * matrix_int_det(matrix_without_row(&sub_matrix, matrix, row));
+
+
+  free(sub_matrix.elements);
+  return det;
+}
+
+IntVector matrix_int_det(IntSquareMatrix *matrix) {
+  assert(matrix->dim > 0);
+  switch (matrix->dim) {
+    case 1:
+      return matrix->elements[0][0];
+
+    case 2:
+      return matrix->elements[0][0] * matrix->elements[1][1] - matrix->elements[0][1] * matrix->elements[1][0];
+
+    default:
+      return det_reduce(matrix);
+  }
+}
+
+void matrix_reshape(IntVector **bi_dim, IntVector *flat, int width, int height) {
+  int row;
+  assert(width > 0 && height > 0);
+
+  for (row = 0; row < height; ++row)
+    bi_dim[row] = flat + row * width;
+}
-- 
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