[hackers] [libzahl] 64-bit chars out-perform 32-bit chars on almost all operations, and on all expensive operations || Mattias Andrée

[git]

commit 5e77b994435be4bef66ff596bf931e1fff97a77c
Author:     Mattias Andrée <maand...@kth.se>
AuthorDate: Sat Mar 12 20:22:11 2016 +0100
Commit:     Mattias Andrée <maand...@kth.se>
CommitDate: Sat Mar 12 20:22:11 2016 +0100

    64-bit chars out-perform 32-bit chars on almost all operations, and on all 
expensive operations
    
    Signed-off-by: Mattias Andrée <maand...@kth.se>

diff --git a/src/internals.h b/src/internals.h
index 8a9c379..b4e6039 100644
--- a/src/internals.h
+++ b/src/internals.h
@@ -5,9 +5,9 @@
 #include <stdlib.h>
 #include <errno.h>
 
-#define BITS_PER_CHAR                32
-#define LB_BITS_PER_CHAR             5
-#define ZAHL_CHAR_MAX                UINT32_MAX
+#define BITS_PER_CHAR                64
+#define LB_BITS_PER_CHAR             6
+#define ZAHL_CHAR_MAX                UINT64_MAX
 
 #define FLOOR_BITS_TO_CHARS(bits)    ((bits) >> LB_BITS_PER_CHAR)
 #define CEILING_BITS_TO_CHARS(bits)  (((bits) + (BITS_PER_CHAR - 1)) >> 
LB_BITS_PER_CHAR)
diff --git a/src/zsets.c b/src/zsets.c
index 2b91864..fb44db4 100644
--- a/src/zsets.c
+++ b/src/zsets.c
@@ -41,9 +41,6 @@ zsets(z_t a, const char *str)
                        if (!temp)
                                continue;
                        libzahl_tmp_str_num->chars[0] = (zahl_char_t)temp;
-                       temp >>= BITS_PER_CHAR;
-                       libzahl_tmp_str_num->chars[1] = (zahl_char_t)temp;
-                       libzahl_tmp_str_num->used = 1 + !!temp;
                        zadd(a, a, libzahl_tmp_str_num);
                }
        }
diff --git a/src/zsetu.c b/src/zsetu.c
index 37fbf7c..538ea37 100644
--- a/src/zsetu.c
+++ b/src/zsetu.c
@@ -13,9 +13,6 @@ zsetu(z_t a, unsigned long long int b)
        }
        ENSURE_SIZE(a, SIZE_MULTIPLE(b, *(a->chars)));
        SET_SIGNUM(a, 1);
-       a->used = 0;
-       while (b) {
-               a->chars[a->used++] = (zahl_char_t)b;
-               b >>= BITS_PER_CHAR;
-       }
+       a->chars[0] = (zahl_char_t)b;
+       a->used = 1;
 }
diff --git a/src/zstr.c b/src/zstr.c
index f7273ce..81a9674 100644
--- a/src/zstr.c
+++ b/src/zstr.c
@@ -6,16 +6,16 @@
 #define num  libzahl_tmp_str_num
 #define rem  libzahl_tmp_str_rem
 
-/* All 9 you see here is derived from that 10⁹ is the largest
- * power of than < 2³², and 32 is the number of bits in
- * zahl_char_t. If zahl_char_t is chanced, the value 9, and
- * the cast to unsigned long must be changed accordingly. */
+/* All 19 you see here is derived from that 10¹⁹ is the largest
+ * power of than < 2⁶⁴, and 64 is the number of bits in
+ * zahl_char_t. If zahl_char_t is chanced, the value 19, and
+ * the cast to unsigned long long must be changed accordingly. */
 
 
 char *
 zstr(z_t a, char *b)
 {
-       char buf[9 + 1];
+       char buf[19 + 1];
        size_t n, len;
        char overridden = 0;
        int neg;
@@ -44,17 +44,17 @@ zstr(z_t a, char *b)
        b[0] = '-';
        b += neg;
        n -= neg;
-       n = n > 9 ? (n - 9) : 0;
+       n = n > 19 ? (n - 19) : 0;
 
        for (;;) {
-               zdivmod(num, rem, num, libzahl_const_1e9);
+               zdivmod(num, rem, num, libzahl_const_1e19);
                if (!zzero(num)) {
-                       sprintf(b + n, "%09lu", zzero(rem) ? 0UL : (unsigned 
long)(rem->chars[0]));
-                       b[n + 9] = overridden;
+                       sprintf(b + n, "%019llu", zzero(rem) ? 0ULL : (unsigned 
long long)(rem->chars[0]));
+                       b[n + 19] = overridden;
                        overridden = b[n];
-                       n = n > 9 ? (n - 9) : 0;
+                       n = n > 19 ? (n - 19) : 0;
                } else {
-                       len = (size_t)sprintf(buf, "%lu", (unsigned 
long)(rem->chars[0]));
+                       len = (size_t)sprintf(buf, "%llu", (unsigned long 
long)(rem->chars[0]));
                        if (overridden)
                                buf[len] = b[n + len];
                        memcpy(b + n, buf, len + 1);
diff --git a/zahl.h b/zahl.h
index 4cb1373..f537c23 100644
--- a/zahl.h
+++ b/zahl.h
@@ -11,7 +11,7 @@
 
 
 /* You should pretend like this typedef does not exist. */
-typedef uint32_t zahl_char_t;
+typedef uint64_t zahl_char_t;
 
 /* This structure should be considered opaque. */
 typedef struct {