Add C++ implementations of ilaclc, ilaclr, iladlc, iladlr, ilaslc, ilaslr, ilazlc, ilazlr.
These functions are purely combinatorial and are used to find the first non-zero column/row of a matrix.
PiperOrigin-RevId: 381023007
diff --git a/lapack/experimental/ilaxly.cpp b/lapack/experimental/ilaxly.cpp
new file mode 100644
index 0000000..c2e56a2
--- /dev/null
+++ b/lapack/experimental/ilaxly.cpp
@@ -0,0 +1,96 @@
+#include "../../Eigen/Core"
+
+extern "C" {
+int ilaslc_(int *m, int *n, float *a, int *lda);
+int iladlc_(int *m, int *n, double *a, int *lda);
+int ilaclc_(int *m, int *n, std::complex<float> *a, int *lda);
+int ilazlc_(int *m, int *n, std::complex<double> *a, int *lda);
+int ilaslr_(int *m, int *n, float *a, int *lda);
+int iladlr_(int *m, int *n, double *a, int *lda);
+int ilaclr_(int *m, int *n, std::complex<float> *a, int *lda);
+int ilazlr_(int *m, int *n, std::complex<double> *a, int *lda);
+}
+
+using Eigen::ColMajor;
+using Eigen::Dynamic;
+using Eigen::Map;
+using Eigen::Matrix;
+using Eigen::OuterStride;
+
+// Scan a matrix for its last non-zero column.
+template <typename T>
+int ilaxlc(const int m, const int n, T *a, const int lda) {
+ if (n == 0) return 0;
+ using MatrixType =
+ Map<Matrix<T, Dynamic, Dynamic, ColMajor>, 0, OuterStride<>>;
+ MatrixType a_matrix(a, m, n, OuterStride<>(lda));
+
+ // Quick test for the common case where one corner is non-zero.
+ if ((a_matrix(0, n - 1) != T(0)) || (a_matrix(m - 1, n - 1) != T(0))) {
+ return n;
+ }
+
+ // Now scan each column from the end, returning with the first non-zero.
+ int c = n - 1;
+ for (; c >= 0; --c) {
+ if ((a_matrix.array().col(c) != T(0)).any()) {
+ break;
+ }
+ }
+ return c + 1;
+}
+
+int ilaslc_(int *m, int *n, float *a, int *lda) {
+ return ilaxlc(*m, *n, a, *lda);
+}
+
+int iladlc_(int *m, int *n, double *a, int *lda) {
+ return ilaxlc(*m, *n, a, *lda);
+}
+
+int ilaclc_(int *m, int *n, std::complex<float> *a, int *lda) {
+ return ilaxlc(*m, *n, a, *lda);
+}
+
+int ilazlc_(int *m, int *n, std::complex<double> *a, int *lda) {
+ return ilaxlc(*m, *n, a, *lda);
+}
+
+// Scan a matrix for its last non-zero row.
+template <typename T>
+int ilaxlr(const int m, const int n, T *a, const int lda) {
+ if (m == 0) return m;
+ using MatrixType =
+ Map<Matrix<T, Dynamic, Dynamic, ColMajor>, 0, OuterStride<>>;
+ MatrixType a_matrix(a, m, n, OuterStride<>(lda));
+
+ // Quick test for the common case where one corner is non-zero.
+ if ((a_matrix(m - 1, 0) != T(0)) || (a_matrix(m - 1, n - 1) != T(0))) {
+ return m;
+ }
+
+ // Now scan each rowfrom the end, returning with the first non-zero.
+ int r = m - 1;
+ for (; r >= 0; --r) {
+ if ((a_matrix.array().row(r) == T(0)).any()) {
+ break;
+ }
+ }
+ return r + 1;
+}
+
+int ilaslr_(int *m, int *n, float *a, int *lda) {
+ return ilaxlr(*m, *n, a, *lda);
+}
+
+int iladlr_(int *m, int *n, double *a, int *lda) {
+ return ilaxlr(*m, *n, a, *lda);
+}
+
+int ilaclr_(int *m, int *n, std::complex<float> *a, int *lda) {
+ return ilaxlr(*m, *n, a, *lda);
+}
+
+int ilazlr_(int *m, int *n, std::complex<double> *a, int *lda) {
+ return ilaxlr(*m, *n, a, *lda);
+}
