testint128.c

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/*-------------------------------------------------------------------------
 *
 * testint128.c
 *    Testbed for roll-our-own 128-bit integer arithmetic.
 *
 * This is a standalone test program that compares the behavior of an
 * implementation in int128.h to an (assumed correct) int128 native type.
 *
 * Copyright (c) 2017-2025, PostgreSQL Global Development Group
 *
 *
 * IDENTIFICATION
 *    src/tools/testint128.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres_fe.h"
 
/*
 * By default, we test the non-native implementation in int128.h; but
 * by predefining USE_NATIVE_INT128 to 1, you can test the native
 * implementation, just to be sure.
 */
#ifndef USE_NATIVE_INT128
#define USE_NATIVE_INT128 0
#endif
 
#include "common/int128.h"
#include "common/pg_prng.h"
 
/*
 * We assume the parts of this union are laid out compatibly.
 */
typedef union
{
    int128      i128;
    INT128      I128;
    union
    {
#ifdef WORDS_BIGENDIAN
        int64       hi;
        uint64      lo;
#else
        uint64      lo;
        int64       hi;
#endif
    }           hl;
}           test128;
 
 
/*
 * Control version of comparator.
 */
static inline int
my_int128_compare(int128 x, int128 y)
{
    if (x < y)
        return -1;
    if (x > y)
        return 1;
    return 0;
}
 
/*
 * Main program.
 *
 * Generates a lot of random numbers and tests the implementation for each.
 * The results should be reproducible, since we use a fixed PRNG seed.
 *
 * You can give a loop count if you don't like the default 1B iterations.
 */
int
main(int argc, char **argv)
{
    long        count;
 
    pg_prng_seed(&pg_global_prng_state, 0);
 
    if (argc >= 2)
        count = strtol(argv[1], NULL, 0);
    else
        count = 1000000000;
 
    while (count-- > 0)
    {
        int64       x = pg_prng_uint64(&pg_global_prng_state);
        int64       y = pg_prng_uint64(&pg_global_prng_state);
        int64       z = pg_prng_uint64(&pg_global_prng_state);
        test128     t1;
        test128     t2;
 
        /* check unsigned addition */
        t1.hl.hi = x;
        t1.hl.lo = y;
        t2 = t1;
        t1.i128 += (int128) (uint64) z;
        int128_add_uint64(&t2.I128, (uint64) z);
 
        if (t1.hl.hi != t2.hl.hi || t1.hl.lo != t2.hl.lo)
        {
            printf("%016lX%016lX + unsigned %lX\n", x, y, z);
            printf("native = %016lX%016lX\n", t1.hl.hi, t1.hl.lo);
            printf("result = %016lX%016lX\n", t2.hl.hi, t2.hl.lo);
            return 1;
        }
 
        /* check signed addition */
        t1.hl.hi = x;
        t1.hl.lo = y;
        t2 = t1;
        t1.i128 += (int128) z;
        int128_add_int64(&t2.I128, z);
 
        if (t1.hl.hi != t2.hl.hi || t1.hl.lo != t2.hl.lo)
        {
            printf("%016lX%016lX + signed %lX\n", x, y, z);
            printf("native = %016lX%016lX\n", t1.hl.hi, t1.hl.lo);
            printf("result = %016lX%016lX\n", t2.hl.hi, t2.hl.lo);
            return 1;
        }
 
        /* check multiplication */
        t1.i128 = (int128) x * (int128) y;
 
        t2.hl.hi = t2.hl.lo = 0;
        int128_add_int64_mul_int64(&t2.I128, x, y);
 
        if (t1.hl.hi != t2.hl.hi || t1.hl.lo != t2.hl.lo)
        {
            printf("%lX * %lX\n", x, y);
            printf("native = %016lX%016lX\n", t1.hl.hi, t1.hl.lo);
            printf("result = %016lX%016lX\n", t2.hl.hi, t2.hl.lo);
            return 1;
        }
 
        /* check comparison */
        t1.hl.hi = x;
        t1.hl.lo = y;
        t2.hl.hi = z;
        t2.hl.lo = pg_prng_uint64(&pg_global_prng_state);
 
        if (my_int128_compare(t1.i128, t2.i128) !=
            int128_compare(t1.I128, t2.I128))
        {
            printf("comparison failure: %d vs %d\n",
                   my_int128_compare(t1.i128, t2.i128),
                   int128_compare(t1.I128, t2.I128));
            printf("arg1 = %016lX%016lX\n", t1.hl.hi, t1.hl.lo);
            printf("arg2 = %016lX%016lX\n", t2.hl.hi, t2.hl.lo);
            return 1;
        }
 
        /* check case with identical hi parts; above will hardly ever hit it */
        t2.hl.hi = x;
 
        if (my_int128_compare(t1.i128, t2.i128) !=
            int128_compare(t1.I128, t2.I128))
        {
            printf("comparison failure: %d vs %d\n",
                   my_int128_compare(t1.i128, t2.i128),
                   int128_compare(t1.I128, t2.I128));
            printf("arg1 = %016lX%016lX\n", t1.hl.hi, t1.hl.lo);
            printf("arg2 = %016lX%016lX\n", t2.hl.hi, t2.hl.lo);
            return 1;
        }
    }
 
    return 0;
}