Simplified code a bit

mp_cutoffs.c

@@ -8,7 +8,8 @@
 int MP_MUL_KARATSUBA_CUTOFF = MP_DEFAULT_MUL_KARATSUBA_CUTOFF,
     MP_SQR_KARATSUBA_CUTOFF = MP_DEFAULT_SQR_KARATSUBA_CUTOFF,
     MP_MUL_TOOM_CUTOFF = MP_DEFAULT_MUL_TOOM_CUTOFF,
-    MP_SQR_TOOM_CUTOFF = MP_DEFAULT_SQR_TOOM_CUTOFF;
+    MP_SQR_TOOM_CUTOFF = MP_DEFAULT_SQR_TOOM_CUTOFF,
+    MP_RADIX_CUTOFF = MP_DEFAULT_RADIX_CUTOFF;
 #endif
 
 #endif

mp_to_radix.c

@@ -50,7 +50,7 @@ mp_err mp_to_radix(const mp_int *a, char *str, size_t maxlen, size_t *written, i
             Include branches fror them and/or (tunable?) cutoff? */
 
    /* TODO: check if it can be done better */
-   if (MP_HAS(S_MP_FASTER_TO_RADIX)) {
+   if (MP_HAS(S_MP_FASTER_TO_RADIX) && (a->used > (MP_RADIX_CUTOFF / MP_DIGIT_BIT))) {
       if ((err = s_mp_faster_to_radix(&a_bar, str, maxlen, &part_written, radix)) != MP_OKAY)            goto LBL_ERR;
    } else if (MP_HAS(S_MP_SLOWER_TO_RADIX)) {
       char *start = str;

s_mp_faster_to_radix.c

@@ -134,7 +134,7 @@ mp_err s_mp_faster_to_radix(const mp_int *a, char *str, size_t maxlen, size_t *w
 
    /* Cutoff at about twice the size of P[0]. */
    /* TODO: Check if it makes sense to make it tunable. */
-   if (ilog2a < (2 * k * MP_RADIX_BARRETT_START_MULTIPLICATOR)) {
+   if (ilog2a < (2 * k)) {
       if ((err = s_mp_slower_to_radix(a, sptr, &part_maxlen, &part_written, radix, false)) != MP_OKAY)   goto LTM_ERR;
       /* part_written does not count EOS */
       *written = part_written + 1;
@@ -165,18 +165,8 @@ mp_err s_mp_faster_to_radix(const mp_int *a, char *str, size_t maxlen, size_t *w
       with R_0 = (2^(2*k))/b^y and k = ceil(log_2(n)) as computed above.
     */
 
-   /* To get the tree a bit flatter. Alternative: do it iteratively instead of recursively */
-   k = k * MP_RADIX_BARRETT_START_MULTIPLICATOR;
-
    /* Compute initial reciprocal R[0] and expand it (R[0]^(2^k) */
    if ((err = mp_init_i32(&P[0], n)) != MP_OKAY)                                                         goto LTM_ERR;
-   /* TODO: chunksize does not seem to matter much above the initial b^y, d.n.f.t. remove this line if
-            MP_RADIX_BARRETT_START_MULTIPLICATOR  is removed but don't forget the possibility that
-            the OS does not like too many recursions. This routine does use a lot of stack
-            and it calls other D&C algorithms (fast multiplication, fast division) that need a little
-            slice of the stack, too (vid.: ulimit -s) */
-   if ((err = mp_expt_n(&P[0], MP_RADIX_BARRETT_START_MULTIPLICATOR, &P[0])) != MP_OKAY)                 goto LTM_ERR;
-
    if ((err = mp_init(&R[0])) != MP_OKAY)                                                                goto LTM_ERR;
    if ((err = mp_2expt(&R[0], 2*k)) != MP_OKAY)                                                          goto LTM_ERR;
    if ((err = mp_div(&R[0], &P[0], &R[0], NULL)) != MP_OKAY)                                             goto LTM_ERR;

s_mp_slower_to_radix.c

@@ -26,9 +26,7 @@ mp_err s_mp_slower_to_radix(const mp_int *a, char **str, size_t *part_maxlen, si
 
    /* The number of digits of "radix" to be filled if this chunk is not the most significant one. */
    if (pad) {
-      /* TODO: Disconnect  MP_RADIX_BARRETT_START_MULTIPLICATOR from this branch and use a different macro.
-               Check if it makes sense to make that replacement tunable */
-      ybar = s_mp_radix_exponent_y[radix] * MP_RADIX_BARRETT_START_MULTIPLICATOR;
+      ybar = s_mp_radix_exponent_y[radix];
    }
 
    if ((err = mp_init_copy(&t, a)) != MP_OKAY)                                                           goto LTM_ERR;

tommath.h

@@ -121,13 +121,12 @@ extern int
 MP_MUL_KARATSUBA_CUTOFF,
 MP_SQR_KARATSUBA_CUTOFF,
 MP_MUL_TOOM_CUTOFF,
-MP_SQR_TOOM_CUTOFF;
+MP_SQR_TOOM_CUTOFF,
+MP_RADIX_CUTOFF;
 #endif
 
-/* Might be tunable. See comments in s_mp_faster_to_radix.c */
-#ifndef MP_RADIX_BARRETT_START_MULTIPLICATOR
-#   define MP_RADIX_BARRETT_START_MULTIPLICATOR   10
-#endif
+
+
 
 /* define this to use lower memory usage routines (exptmods mostly) */
 /* #define MP_LOW_MEM */

tommath_cutoffs.h

@@ -11,3 +11,4 @@
 #define MP_DEFAULT_SQR_KARATSUBA_CUTOFF 120
 #define MP_DEFAULT_MUL_TOOM_CUTOFF      350
 #define MP_DEFAULT_SQR_TOOM_CUTOFF      400
+#define MP_DEFAULT_RADIX_CUTOFF         600