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Fix statistical seed bias, off-by-one range errors, and resource handling bugs #1

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Merged
feinorgh merged 3 commits into from
Mar 5, 2026
Merged

Fix statistical seed bias, off-by-one range errors, and resource handling bugs #1

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baaea99
Initial plan
Copilot Mar 5, 2026
7c6e884
Initial plan for performance, statistical correctness, and compatibil…
Copilot Mar 5, 2026
7665cde
Fix performance, statistical correctness, and compatibility issues in…
Copilot Mar 5, 2026
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1 change: 1 addition & 0 deletions .gitignore
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
random
76 changes: 55 additions & 21 deletions random.c
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Expand Up @@ -93,6 +93,7 @@ clear_number(void *p)
void
treeaction(const void *nodep, const VISIT which, const int depth)
{
(void)depth;
mpz_t *datap;
switch(which) {
case preorder:
Expand All @@ -111,10 +112,9 @@ treeaction(const void *nodep, const VISIT which, const int depth)
}

void
random_integer(mpz_t result, const mpz_t low, const mpz_t high)
random_integer(mpz_t result, const mpz_t low)
{
mpz_sub(range, high, low);
mpz_add_ui(range, range, 1);
/* range = high - low + 1 (inclusive count) is already set globally */
mpz_urandomm(result, state, range);
mpz_add(result, result, low);
}
Expand All @@ -129,15 +129,19 @@ generate_series(size_t size_of_set, mpz_t low, mpz_t high)
{
char *suffix = "s";
if (verbose) {
char *low_str = mpz_get_str(NULL, 10, low);
char *high_str = mpz_get_str(NULL, 10, high);
if (size_of_set < 2) {
suffix = "";
}
printf("Generating %zu number%s between %s and %s...\n",
size_of_set,
suffix,
mpz_get_str(NULL, 10, low),
mpz_get_str(NULL, 10, high)
low_str,
high_str
);
free(low_str);
free(high_str);
}

mpz_t tmp;
Expand All @@ -153,28 +157,32 @@ generate_series(size_t size_of_set, mpz_t low, mpz_t high)
* */
mpz_sub_ui(tmp, range, size_of_set);
size_t invsize = mpz_get_ui(tmp);
mpz_t *number = malloc(sizeof(mpz_t) * invsize);
mpz_t *number = NULL;
if (invsize > 0) {
number = malloc(sizeof(mpz_t) * invsize);
if (number == NULL) {
fprintf(stderr, "%s\n", strerror(errno));
exit(1);
}
}
void *root = NULL;
size_t i = 0;
for ( i = 0; i < invsize; i++ ) {
mpz_init(number[i]);
do {
random_integer(number[i], low, high);
random_integer(number[i], low);
} while (tfind((void *)number[i], &root, compare) != NULL);
tsearch((void *)number[i], &root, compare);
}
mpz_set(tmp, low);
while (mpz_cmp(tmp, high)) {
while (mpz_cmp(tmp, high) <= 0) {
if (tfind((void *)tmp, &root, compare) == NULL) {
/* printf("%s\n", mpz_get_str(NULL, 10, tmp)); */
gmp_printf("%Zd\n", tmp);
}
mpz_add_ui(tmp, tmp, 1);
}
tdestroy(root, clear_number);
if (number != NULL) {
free(number);
}
free(number);
} else {
mpz_t *number = malloc(sizeof(mpz_t) * size_of_set);
if (number == NULL) {
Expand All @@ -186,16 +194,14 @@ generate_series(size_t size_of_set, mpz_t low, mpz_t high)
for ( i = 0; i < size_of_set; i++ ) {
mpz_init(number[i]);
do {
random_integer(number[i], low, high);
random_integer(number[i], low);
} while (tfind((void *)number[i], &root, compare) != NULL);
tsearch((void *)number[i], &root, compare);
}

twalk(root, treeaction);
tdestroy(root, clear_number);
if (number != NULL) {
free(number);
}
free(number);
}
mpz_clear(tmp);
}
Expand All @@ -209,7 +215,11 @@ init_random(void)
mpz_init(seed);

size_t count = 256; /* We read this many bytes from /dev/urandom */
char *seedstart = malloc(count*sizeof(char*) + 1);
char *seedstart = malloc(count + 1);
if (seedstart == NULL) {
fprintf(stderr, "%s\n", strerror(errno));
exit(1);
}

char *filename;
if (userandom) {
Expand All @@ -219,9 +229,30 @@ init_random(void)
}

int devrandom = open(filename, O_RDONLY);
read(devrandom, seedstart, count);
if (devrandom < 0) {
fprintf(stderr, "%s: %s\n", filename, strerror(errno));
free(seedstart);
exit(1);
}
size_t total = 0;
while (total < count) {
ssize_t n = read(devrandom, seedstart + total, count - total);
if (n < 0) {
fprintf(stderr, "%s: %s\n", filename, strerror(errno));
free(seedstart);
close(devrandom);
exit(1);
}
if (n == 0) {
fprintf(stderr, "%s: unexpected end of file\n", filename);
free(seedstart);
close(devrandom);
exit(1);
}
total += (size_t)n;
}
close(devrandom);
mpz_import(seed, 1, 1, 1, 0, 0, seedstart);
mpz_import(seed, count, 1, sizeof(char), 0, 0, seedstart);
free(seedstart);

gmp_randseed(state, seed);
Expand Down Expand Up @@ -345,13 +376,15 @@ parse_options(int argc, char * const argv[])
break;
case 'r':
userandom = 1;
break;
case '?':
break;
}
}
mpz_init(range);
/* range = high - low + 1 (total count of integers in the inclusive range) */
mpz_sub(range, high, low);
if(mpz_cmp(arg_count, range) >= 0) {
mpz_add_ui(range, range, 1);
if(mpz_cmp(arg_count, range) > 0) {
fprintf(stderr, "Error: Size given (%s) exceeds range (%s).\n"
"No unique random numbers can be generated.\n",
mpz_get_str(NULL, 10, arg_count),
Expand All @@ -369,6 +402,7 @@ main(int argc, const char **argv)
{
mpz_init_set_str(low, "1", 10);
mpz_init_set_str(high, "100", 10);
mpz_init(range);
parse_options(argc, (char * const*)argv);
init_random();
generate_series(size_of_set, low, high);
Expand Down