From 0f6f4c9db81ce100baa2502075dc611fa50aa116 Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Sun, 3 Apr 2016 12:53:41 +0200
Subject: Implement deterministic justification

i.e. the mersenne twister seed now depends on the data.
---
 src/line_accumulator.cc | 26 +++++++++++++++-----------
 src/line_accumulator.h  |  4 +---
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/src/line_accumulator.cc b/src/line_accumulator.cc
index 0abe1a4..9922f04 100644
--- a/src/line_accumulator.cc
+++ b/src/line_accumulator.cc
@@ -6,23 +6,29 @@
 
 namespace {
 
+static std::mt19937 generator;
+
 std::uint8_t getRandomIndex(
-	std::mt19937&      random,
+	const int          seed,
 	const std::uint8_t n
 ) {
-	return std::uniform_int_distribution<std::uint8_t>{0, n}(random);
+	generator.seed(seed);
+
+	return std::uniform_int_distribution<std::uint8_t>{0, n}(generator);
 }
 
 std::vector<std::uint8_t> getRandomIndizes(
-	std::mt19937&      random,
+	const int          seed,
 	const std::uint8_t n
 ) {
+	generator.seed(seed);
+
 	std::vector<std::uint8_t> indizes(n);
 	std::iota(indizes.begin(), indizes.end(), 0);
 	std::shuffle(
 		indizes.begin(),
 		indizes.end(),
-		random
+		generator
 	);
 
 	return indizes;
@@ -34,8 +40,6 @@ namespace justify {
 
 LineAccumulator::LineAccumulator(const std::uint8_t max_length):
 	max_length_{max_length},
-	device_{},
-	random_{device_()},
 	length_{0},
 	tokens_{} { }
 
@@ -62,6 +66,9 @@ void LineAccumulator::operator()(const std::string& token) {
 }
 
 void LineAccumulator::justify() {
+	const int seed = this->tokens_.size()
+	               + this->getMissing();
+
 	switch ( this->tokens_.size() ) {
 		// There is no sensible block justification of null or any single token
 		case 0:
@@ -105,16 +112,13 @@ void LineAccumulator::justify() {
 		// randomly distribute missing spaces
 		case 1: {
 			this->tokens_[
-				getRandomIndex(this->random_, this->tokens_.size() - 2)
+				getRandomIndex(seed, this->tokens_.size() - 2)
 			].second += 1;
 
 			break;
 		}
 		default: {
-			const auto indizes = getRandomIndizes(
-				this->random_,
-				this->tokens_.size() - 2
-			);
+			const auto indizes = getRandomIndizes(seed, this->tokens_.size() - 2);
 
 			std::for_each(
 				indizes.begin(),
diff --git a/src/line_accumulator.h b/src/line_accumulator.h
index cb07210..2ca271c 100644
--- a/src/line_accumulator.h
+++ b/src/line_accumulator.h
@@ -19,9 +19,7 @@ class LineAccumulator {
 	private:
 		const std::uint8_t max_length_;
 
-		std::random_device device_;
-		std::mt19937       random_;
-		std::uint8_t       length_;
+		std::uint8_t length_;
 
 		std::vector<
 			std::pair<std::string, std::uint8_t>
-- 
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