6′19″ runtime, not the best but not too shabby on X61@1.8GHz

2024/22/ilist

+../../i2c/ilist
\ No newline at end of file

2024/22/s1.c

+/* ./ilist 'unsigned int' */
+
+#include <err.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "inputs.h"
+
+#define NELEM(a) (sizeof(a) / sizeof((a)[0]))
+#define N NELEM(I)
+
+int
+main(void)
+{
+	size_t n;
+	unsigned long long res;
+
+	res = 0;
+	for (n = 0; n < N; ++n) {
+		register unsigned long long x, y, z;
+
+#define mix() do {		\
+	x ^= y;			\
+} while (/* CONSTCOND */ 0)
+#define prune() do {		\
+	x &= 16777215;		\
+} while (/* CONSTCOND */ 0)
+
+		x = I[n];
+		for (z = 0; z < 2000U; ++z) {
+			y = x * 64U;
+			mix();
+			prune();
+			y = x / 32U;
+			mix();
+			prune();
+			y = x * 2048U;
+			mix();
+			prune();
+		}
+		res += x;
+		printf("%u: %u\n", I[n], (unsigned)x);
+	}
+	printf("%llu\n", res);
+	return (0);
+}

2024/22/s2.c

+/* echo 123 >c2 */
+/* printf '%u\n' 1 2 3 2024 >c3 */
+/* ./ilist 'unsigned int' */
+
+#define _GNU_SOURCE
+#include <err.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "inputs.h"
+
+#define NELEM(a) (sizeof(a) / sizeof((a)[0]))
+#define N NELEM(I)
+
+#ifdef EX2
+#define R 10U
+#else
+#define R 2000U
+#endif
+
+static unsigned char p[N][R] = {0};
+static signed char pd[N][R] = {0};
+
+int
+main(void)
+{
+	size_t n;
+	unsigned long bestres = 0;
+	signed char seq[4];
+	signed char best[4] /* GCC… */ = { -66, -66, -66, -66 };
+
+	for (n = 0; n < N; ++n) {
+		register unsigned long long x, y, z;
+		unsigned char o;
+
+#define mix() do {		\
+	x ^= y;			\
+} while (/* CONSTCOND */ 0)
+#define prune() do {		\
+	x &= 16777215;		\
+} while (/* CONSTCOND */ 0)
+
+		x = I[n];
+#ifdef EX2
+		printf("%8u: %u\n", (unsigned)x, (unsigned)(x % 10));
+#endif
+		for (z = 0; z < R; ++z) {
+			o = x % 10;
+			y = x * 64U;
+			mix();
+			prune();
+			y = x / 32U;
+			mix();
+			prune();
+			y = x * 2048U;
+			mix();
+			prune();
+			p[n][z] = x % 10U;
+			pd[n][z] = (int)p[n][z] - (int)o;
+#ifdef EX2
+			printf("%8u: %u (%d)\n", (unsigned)x,
+			    (unsigned)p[n][z], (int)pd[n][z]);
+#endif
+		}
+	}
+
+#ifdef EX2
+	printf("D: p\tpd\tfor #0\n");
+	for (n = 0; n < R; ++n)
+		printf("   %u\t%d\n", (unsigned)p[0][n], (int)pd[0][n]);
+#endif
+
+	printf("trying…\n");
+	for (seq[0] = -9; seq[0] <= 9; ++seq[0])
+		for (seq[1] = -9; seq[1] <= 9; ++seq[1])
+			for (seq[2] = -9; seq[2] <= 9; ++seq[2])
+				for (seq[3] = -9; seq[3] <= 9; ++seq[3]) {
+					unsigned long res = 0;
+
+					for (n = 0; n < N; ++n) {
+						const signed char *fp;
+
+						fp = memmem(pd[n] + 1U,
+						    R - 1U,
+						    seq, 4U);
+						if (!fp)
+							continue;
+#ifdef EX2
+						printf("\t%zu got %d,%d,%d,%d at %zu: %u\n",
+						    n, seq[0], seq[1], seq[2], seq[3],
+						    (size_t)(fp - pd[n]),
+						    p[n][(size_t)(fp - pd[n]) + 3U]);
+#endif
+						res += p[n][(size_t)(fp - pd[n]) + 3U];
+					}
+					if (res > bestres) {
+						printf("new best %d,%d,%d,%d ⇒ %lu\n",
+						    seq[0], seq[1], seq[2], seq[3], res);
+						best[0] = seq[0];
+						best[1] = seq[1];
+						best[2] = seq[2];
+						best[3] = seq[3];
+						bestres = res;
+					}
+				}
+	printf("done: %d,%d,%d,%d ⇒ %lu\n",
+	    best[0], best[1], best[2], best[3], bestres);
+	return (0);
+}

i2c/ilist

+#!/bin/mksh
+if [[ -z $1 ]]; then
+	print -r -- "E: syntax: ${0##*/} <data type> (e.g. 'unsigned long long')"
+	exit 1
+fi
+set -o noglob
+dtype=$1
+set -e
+doone() {
+	print -r -- 'static const' $dtype 'I[] = {'
+	sed -e $'s/^/\t/' -e 's/$/,/' <"$1"
+	print -r -- '};'
+}
+exec >inputs.h
+print '#ifndef PROD'
+print
+if [[ -s c2 ]]; then
+	print '#if defined(EX2)'
+	doone c2
+	for t in 3 4 5 6 7 8 9; do
+		if [[ -s c$t ]]; then
+			print "#elif defined(EX$t)"
+			doone c$t
+		fi
+	done
+	print '#else'
+	doone c
+	print '#endif'
+else
+	doone c
+fi
+print
+print '#else'
+print
+doone i
+print
+print '#endif'
+exec >/dev/null
+exit 0