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@bobjansen bobjansen/plain_R.R
Last active Jun 8, 2019

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FastR experiments with Sudoku code extracted (Rcpp ignored)
sudokuTxt <- "
1 0 0 0 0 0 0 0 6
0 0 6 0 2 0 7 0 0
7 8 9 4 5 0 1 0 3
0 0 0 8 0 7 0 0 4
0 0 0 0 3 0 0 0 0
0 9 0 0 0 4 2 0 1
3 1 2 9 7 0 0 4 0
0 4 0 0 1 2 0 7 8
9 0 8 0 0 0 0 0 0"
sudoku <- as.matrix(
read.table(text = sudokuTxt,
col.names = letters[1:9]))
library(zeallot)
library(magrittr)
solve <- function(partialSolution, choicesFUN) {
# Eliminate impossible values, give some suggestions
# and flag contradictions.
c(partialSolution, suggestions, contradiction) %<-%
eliminate(partialSolution, choicesFUN)
# If dead end FALSE to trace back, if finished TRUE.
if (contradiction) return(list(FALSE, NULL))
if (all(partialSolution %in% 1:9))
return(list(TRUE, partialSolution))
# Branching, exit when the solution is found.
for (suggestion in suggestions) {
c(result, solution) %<-% solve(suggestion,
choicesFUN)
if (result) return(list(result, solution))
}
list(FALSE, NULL)
}
eliminate <- function(grid, choicesFUN) {
suggestions <- 0:9
for (i in 1:nrow(grid)) { for (j in 1:ncol(grid)) {
if (grid[i, j] == 0L) {
choices <- choicesFUN(grid, i, j)
if (length(choices) == 0L) {
return(list(NULL, NULL, TRUE))
} else if (length(choices) == 1L) {
grid[i, j] <- choices
return(list(grid, list(grid), FALSE))
} else
suggestions <- updateSuggestions(
choices, grid, i, j, suggestions)
}
}}
list(grid, suggestions, FALSE)
}
# Find all the choices allowed by the rules.
findChoices <- function(grid, i, j) {
1:9 %>% setdiff(grid[i, ]) %>%
setdiff(grid[ , j]) %>%
setdiff(grid[i - (i - 1) %% 3L + 0:2,
j - (j - 1) %% 3L + 0:2])
}
# Create a list of grids with suggested next moves.
updateSuggestions <- function(choices, grid, i, j,
lastBest) {
if (length(choices) < length(lastBest))
lapply(choices, function(choice) {
grid[i, j] <- choice; grid
})
else
lastBest
}
solution <- solve(sudoku, findChoices)
if (!solution[[1]]) { cat('Solution not found\n')
} else { print(as.data.frame(solution[[2]])) }
sudokuTxt <- "
8 0 0 0 0 0 0 0 0
0 0 3 6 0 0 0 0 0
0 7 0 0 9 0 2 0 0
0 5 0 0 0 7 0 0 0
0 0 0 0 4 5 7 0 0
0 0 0 1 0 0 0 3 0
0 0 1 0 0 0 0 6 8
0 0 8 5 0 0 0 1 0
0 9 0 0 0 0 4 0 0"
sudoku <- as.matrix(
read.table(text = sudokuTxt,
col.names = letters[1:9]))
solve2 <- function(partialSolution, choicesFUN) {
# Eliminate impossible values, give some suggestions
# and flag contradictions.
elStep <- eliminate(partialSolution, choicesFUN)
# If dead end FALSE to trace back, if finished TRUE.
if (elStep[[3]]) return(list(res = FALSE,
sol = NULL))
if (all(elStep[[1]] %in% 1:9))
return(list(res = TRUE, sol = elStep[[1]]))
# Branching, exit when the solution is found.
for (suggestion in elStep[[2]]) {
ans <- solve2(suggestion, choicesFUN)
if (ans$res) return(ans)
}
list(res = FALSE, sol = NULL)
}
findChoices2 <- function(grid, i, j) {
setdiff(setdiff(setdiff(1:9,
grid[i, ]),
grid[ , j]),
grid[i - (i - 1) %% 3L + 0:2,
j - (j - 1) %% 3L + 0:2])
}
print(microbenchmark::microbenchmark(
solve2(sudoku, findChoices2),
control = list(warmup = 20L)
))
library(microbenchmark)
sqr <- function(x) x * x
f1 <- function() for (n in 1:1000) sqr(runif(1:n))
print(R.version)
print(microbenchmark(f1(), control = list(warmup = 100L)))
#include <Rcpp.h>
using namespace Rcpp;
IntegerMatrix subGrid(IntegerMatrix& x, int i, int j) {
i -= i % 3; j -= j % 3;
return x(Range(i, i + 2), Range(j, j + 2));
}
// [[Rcpp::export]]
IntegerVector findChoicesCpp(IntegerMatrix& x,
int i, int j) {
IntegerVector candidates(9);
std::iota(candidates.begin(), candidates.end(), 1);
// C++ is zero-indexed.
return setdiff(setdiff(setdiff(candidates,
IntegerVector(x(i - 1, _))),
IntegerVector(x(_, j - 1))),
subGrid(x, i - 1, j - 1));
}
library(Rcpp)
library(microbenchmark)
sudokuTxt <- "
8 0 0 0 0 0 0 0 0
0 0 3 6 0 0 0 0 0
0 7 0 0 9 0 2 0 0
0 5 0 0 0 7 0 0 0
0 0 0 0 4 5 7 0 0
0 0 0 1 0 0 0 3 0
0 0 1 0 0 0 0 6 8
0 0 8 5 0 0 0 1 0
0 9 0 0 0 0 4 0 0"
sudoku <- as.matrix(
read.table(text = sudokuTxt,
col.names = letters[1:9]))
eliminate <- function(grid, choicesFUN) {
suggestions <- 0:9
for (i in 1:nrow(grid)) { for (j in 1:ncol(grid)) {
if (grid[i, j] == 0L) {
choices <- choicesFUN(grid, i, j)
if (length(choices) == 0L) {
return(list(NULL, NULL, TRUE))
} else if (length(choices) == 1L) {
grid[i, j] <- choices
return(list(grid, list(grid), FALSE))
} else
suggestions <- updateSuggestions(
choices, grid, i, j, suggestions)
}
}}
list(grid, suggestions, FALSE)
}
updateSuggestions <- function(choices, grid, i, j,
lastBest) {
if (length(choices) < length(lastBest))
lapply(choices, function(choice) {
grid[i, j] <- choice; grid
})
else
lastBest
}
solve2 <- function(partialSolution, choicesFUN) {
# Eliminate impossible values, give some suggestions
# and flag contradictions.
elStep <- eliminate(partialSolution, choicesFUN)
# If dead end FALSE to trace back, if finished TRUE.
if (elStep[[3]]) return(list(res = FALSE,
sol = NULL))
if (all(elStep[[1]] %in% 1:9))
return(list(res = TRUE, sol = elStep[[1]]))
# Branching, exit when the solution is found.
for (suggestion in elStep[[2]]) {
ans <- solve2(suggestion, choicesFUN)
if (ans$res) return(ans)
}
list(res = FALSE, sol = NULL)
}
Rcpp::sourceCpp('sudoku.cpp')
solve2(sudoku, findChoicesCpp)
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