R Under development (unstable) (2024-02-28 r85999 ucrt) -- "Unsuffered Consequences"
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> lcg_get_seed <- port4me:::lcg_get_seed
> lcg_set_seed <- port4me:::lcg_set_seed
> lcg_port <- port4me:::lcg_port
> lcg <- port4me:::lcg
> 
> a <- environment(lcg)[["a"]]
> c <- environment(lcg)[["c"]]
> m <- environment(lcg)[["modulus"]]
> message(sprintf("- LCG parameters (a,c,m): (%d,%d,%d)", a, c, m))
- LCG parameters (a,c,m): (75,74,65537)
> stopifnot(a == 75L, c == 74L, m == 2^16+1)
> 
> 
> message("lcg_port() draws uniformly from {min, ..., max}")
lcg_port() draws uniformly from {min, ..., max}
> 
> assert_lcg_port <- function(min = 1024L, max = 65535L, subset = NULL, seed = 0L) {
+   if (is.null(subset)) {
+     n <- max - min + 1L
+     ports <- min:max
+   } else {
+     min <- min(subset)
+     max <- max(subset)
+     n <- length(subset)
+     ports <- subset
+   }
+   
+   counts <- integer(length = n)
+   names(counts) <- ports
+   
+   lcg_set_seed(seed = seed)
+   
+   for (kk in seq_len(n)) {
+     port <- lcg_port(min = min, max = max, subset = subset)
+     stopifnot(port >= min, port <= max)
+     if (is.null(subset)) {
+       idx <- port - min + 1L
+     } else {
+       idx <- which(port == ports)
+     }
+     stopifnot(!is.na(idx), idx >= 1L, idx <= n)
+     counts[idx] <- counts[idx] + 1L
+   }
+   stopifnot(sum(counts) == n)
+   
+   message("- Distribution of counts:")
+   dist <- table(counts)
+   names(dist) <- sprintf("n=%s", names(dist))
+   print(dist)
+   stopifnot(all(counts == 1L))
+ } ## assert_lcg_port()
> 
> 
> message("lcg_port() draws uniformly from {1024, ..., 65535}")
lcg_port() draws uniformly from {1024, ..., 65535}
> assert_lcg_port()
- Distribution of counts:
  n=1 
64512 
> 
> message("lcg_port() draws uniformly from {1024, ..., 65535} regardless of seed")
lcg_port() draws uniformly from {1024, ..., 65535} regardless of seed
> assert_lcg_port(seed = 1L)
- Distribution of counts:
  n=1 
64512 
> assert_lcg_port(seed = 42L)
- Distribution of counts:
  n=1 
64512 
> assert_lcg_port(seed = 65535L)
- Distribution of counts:
  n=1 
64512 
> 
> message("lcg_port(min = 1) draws uniformly from {1, ..., 65535}")
lcg_port(min = 1) draws uniformly from {1, ..., 65535}
> assert_lcg_port(min = 1)
- Distribution of counts:
  n=1 
65535 
> 
> message("lcg_port(min = 50, max = 100) draws uniformly from {50, ..., 100}")
lcg_port(min = 50, max = 100) draws uniformly from {50, ..., 100}
> assert_lcg_port(min = 50, max = 100)
- Distribution of counts:
n=1 
 51 
> 
> message("lcg_port(subset = 50:100) draws uniformly from {50, ..., 100}")
lcg_port(subset = 50:100) draws uniformly from {50, ..., 100}
> assert_lcg_port(subset = 50:100)
- Distribution of counts:
n=1 
 51 
> 
> message("lcg_port(subset = seq(1, 65535, by = 5)) draws uniformly from {1, 5, ..., 65535}")
lcg_port(subset = seq(1, 65535, by = 5)) draws uniformly from {1, 5, ..., 65535}
> assert_lcg_port(subset = seq(1, 65535, by = 5))
- Distribution of counts:
  n=1 
13107 
> 
> 
> 
> message("lcg() draws from all values in {0, ..., m-1} except one of them")
lcg() draws from all values in {0, ..., m-1} except one of them
> seeds <- 0:(m-1)
> seeds_next <- (a * seeds + c) %% m
> seed_skip <- seeds[seeds_next == seeds]
> message(sprintf(" - Skipped seed: %s", seed_skip))
 - Skipped seed: 65536
> stopifnot(length(seed_skip) == 1L)
> 
> counts <- integer(length = m)
> names(counts) <- seq(from = 0L, to = m - 1L)
> counts[seed_skip + 1L] <- 1L
> 
> seed <- 0L
> message(sprintf("Initializing seed: %d", seed))
Initializing seed: 0
> lcg_set_seed(seed = seed)
[1] 0
> 
> for (kk in seq_len(m - 1L)) {
+   idx <- lcg() + 1L
+   stopifnot(idx >= 1L, idx <= m)
+   counts[idx] <- counts[idx] + 1L
+ }
> 
> stopifnot(sum(counts) == m)
> stopifnot(all(counts > 0L)) ## technically => all(counts == 1)
> 
> 
> message("lcg() draws from uniformly from {0, ..., m-1} except one of them")
lcg() draws from uniformly from {0, ..., m-1} except one of them
> 
> message("- Distribution of counts:")
- Distribution of counts:
> dist <- table(counts)
> names(dist) <- sprintf("n=%s", names(dist))
> print(dist)
  n=1 
65537 
> stopifnot(all(counts == 1L))
> 
> proc.time()
   user  system elapsed 
   9.46    2.71   12.12