add isl_mat_right_kernel

diff --git a/isl_mat.c b/isl_mat.c
index d825e78..bf21732 100644 (file)
--- a/isl_mat.c
+++ b/isl_mat.c
@@ -358,6 +358,35 @@ error:
        return NULL;
 }
 
+struct isl_mat *isl_mat_right_kernel(struct isl_ctx *ctx, struct isl_mat *mat)
+{
+       int i, rank;
+       struct isl_mat *U = NULL;
+       struct isl_mat *K;
+
+       mat = isl_mat_left_hermite(ctx, mat, 0, &U, NULL);
+       if (!mat || !U)
+               goto error;
+
+       for (i = 0, rank = 0; rank < mat->n_col; ++rank) {
+               while (i < mat->n_row && isl_int_is_zero(mat->row[i][rank]))
+                       ++i;
+               if (i >= mat->n_row)
+                       break;
+       }
+       K = isl_mat_alloc(ctx, U->n_row, U->n_col - rank);
+       if (!K)
+               goto error;
+       isl_mat_sub_copy(ctx, K->row, U->row, U->n_row, 0, rank, U->n_col-rank);
+       isl_mat_free(ctx, mat);
+       isl_mat_free(ctx, U);
+       return K;
+error:
+       isl_mat_free(ctx, mat);
+       isl_mat_free(ctx, U);
+       return NULL;
+}
+
 struct isl_mat *isl_mat_lin_to_aff(struct isl_ctx *ctx, struct isl_mat *mat)
 {
        int i;

diff --git a/isl_mat.h b/isl_mat.h
index a243928..5db178b 100644 (file)
--- a/isl_mat.h
+++ b/isl_mat.h
@@ -57,6 +57,7 @@ struct isl_mat *isl_mat_product(struct isl_ctx *ctx,
        struct isl_mat *left, struct isl_mat *right);
 struct isl_mat *isl_mat_right_inverse(struct isl_ctx *ctx,
        struct isl_mat *mat);
+struct isl_mat *isl_mat_right_kernel(struct isl_ctx *ctx, struct isl_mat *mat);
 
 struct isl_mat *isl_mat_drop_cols(struct isl_ctx *ctx, struct isl_mat *mat,
                                unsigned col, unsigned n);