Merge pull request #2640 from fredrik-johansson/n3

Optimize `nmod_mat_lu_classical_delayed`

Author: fredrik-johansson

src/nmod_mat/lu.c

@@ -13,47 +13,42 @@
 #include "nmod_vec.h"
 #include "nmod_mat.h"
 
+#if FLINT_USES_BLAS || (FLINT_BITS == 32) || !defined(__AVX2__)
+
+/* Tuned for Zen 3 with BLAS */
+static const slong lu_cutoff_tab[64] = { 64, 64, 244, 280, 296, 320, 332,
+    792, 800, 800, 800, 400, 400, 400, 400, 404, 404, 400, 408, 416, 400,
+    412, 424, 408, 484, 1352, 1032, 260, 68, 56, 56, 56, 148, 160, 148, 156,
+    156, 156, 120, 168, 160, 124, 156, 124, 156, 148, 112, 156, 148, 136,
+    156, 160, 116, 136, 168, 148, 156, 160, 120, 128, 68, 64, 104, 104 };
+
+#else
+
+/* Tuned for Zen 3 without BLAS */
+static const slong lu_cutoff_tab[64] = { 64, 64, 212, 260, 280, 316, 344,
+    792, 872, 904, 856, 1016, 1136, 1456, 1440, 1464, 1376, 1392, 1448, 1448,
+    1360, 1392, 1400, 1392, 1448, 1416, 1032, 260, 68, 56, 56, 60, 168, 164,
+    152, 152, 156, 148, 148, 148, 152, 164, 160, 148, 164, 148, 164, 160, 160,
+    148, 156, 156, 148, 164, 148, 164, 148, 148, 148, 128, 68, 64, 96, 96 };
+
+#endif
+
 slong
 nmod_mat_lu(slong * P, nmod_mat_t A, int rank_check)
 {
-    slong nrows, ncols, n, cutoff;
-    int bits;
-    nrows = A->r;
-    ncols = A->c;
-
+    slong nrows = A->r, ncols = A->c, n;
     n = FLINT_MIN(nrows, ncols);
 
-    if (n <= 3)
+    if (n <= 3 || (NMOD_BITS(A->mod) > 28 && n <= 7))
     {
         return nmod_mat_lu_classical(P, A, rank_check);
     }
     else
     {
-        if (n >= 20)
-        {
-            bits = NMOD_BITS(A->mod);
-
-            if (bits >= FLINT_BITS - 1)
-                cutoff = 80;
-            else if (bits >= FLINT_BITS / 2 - 2)
-                cutoff = 60;
-            else if (bits >= FLINT_BITS / 4 - 1)
-                cutoff = 180;
-            else
-                cutoff = 60;
-
-            if (n >= cutoff)
-                return nmod_mat_lu_recursive(P, A, rank_check);
-        }
-
-        const dot_params_t params = _nmod_vec_dot_params(n, A->mod);
-
-        // TODO thresholds to re-examine after dot product changes
-        if (params.method <= _DOT1                        // <= 0,1 limb
-                || (params.method <= _DOT2 && n >= 12)    // <= 2 limbs (n >= 12 if exactly 2)
-                || (params.method > _DOT2 && n >= 20))    // == 3 limbs && n >= 20
+        if (n < lu_cutoff_tab[NMOD_BITS(A->mod) - 1])
             return nmod_mat_lu_classical_delayed(P, A, rank_check);
         else
-            return nmod_mat_lu_classical(P, A, rank_check);
+            return nmod_mat_lu_recursive(P, A, rank_check);
     }
 }
+