Cross platform random numbers for samples

benchmark/CMakeLists.txt

@@ -15,8 +15,11 @@ set_target_properties(benchmark PROPERTIES
     C_EXTENSIONS NO
 )
 
-if(MSVC)
-    # target_compile_options(benchmark PRIVATE /experimental:c11atomics)
+if (MSVC)
+	target_compile_options(benchmark PRIVATE /experimental:c11atomics)
+elseif (APPLE)
+    # determinism settings
+    target_compile_options(benchmark PRIVATE -ffp-contract=off)
 endif()
 
 target_link_libraries(benchmark PRIVATE box2d enkiTS)

include/box2d/box2d.h

@@ -521,7 +521,7 @@ B2_API bool b2Shape_AreHitEventsEnabled( b2ShapeId shapeId );
 B2_API bool b2Shape_TestPoint( b2ShapeId shapeId, b2Vec2 point );
 
 /// Ray cast a shape directly
-B2_API b2CastOutput b2Shape_RayCast( b2ShapeId shapeId, b2Vec2 origin, b2Vec2 translation );
+B2_API b2CastOutput b2Shape_RayCast( b2ShapeId shapeId, const b2RayCastInput* input );
 
 /// Get a copy of the shape's circle. Asserts the type is correct.
 B2_API b2Circle b2Shape_GetCircle( b2ShapeId shapeId );

samples/CMakeLists.txt

@@ -97,7 +97,7 @@ set_target_properties(samples PROPERTIES
 
 if (APPLE)
 	# determinism settings
-	target_compile_options(samples PRIVATE -ffp-model=precise -ffp-contract=off)
+	target_compile_options(samples PRIVATE -ffp-contract=off)
 endif()
 
 target_include_directories(samples PRIVATE ${CMAKE_CURRENT_SOURCE_DIR} ${JSMN_DIR})

samples/sample.cpp

@@ -101,6 +101,8 @@ Sample::Sample( Settings& settings )
 	m_maxProfile = {};
 	m_totalProfile = {};
 
+	g_seed = RAND_SEED;
+
 	TestMathCpp();
 }
 
@@ -488,10 +490,12 @@ int RegisterSample( const char* category, const char* name, SampleCreateFcn* fcn
 	return -1;
 }
 
+uint32_t g_seed = RAND_SEED;
+
 b2Polygon RandomPolygon( float extent )
 {
 	b2Vec2 points[b2_maxPolygonVertices];
-	int count = 3 + rand() % 6;
+	int count = 3 + RandomInt() % 6;
 	for ( int i = 0; i < count; ++i )
 	{
 		points[i] = RandomVec2( -extent, extent );

samples/sample.h

@@ -10,8 +10,6 @@
 // todo this include is slow
 #include "TaskScheduler.h"
 
-#include <stdlib.h>
-
 #define ARRAY_COUNT( A ) (int)( sizeof( A ) / sizeof( A[0] ) )
 
 struct Settings;
@@ -113,32 +111,52 @@ extern SampleEntry g_sampleEntries[MAX_SAMPLES];
 extern int g_sampleCount;
 
 #define RAND_LIMIT 32767
+#define RAND_SEED 12345
+
+// Global seed for simple random number generator. This is reset
+// for each sample.
+extern uint32_t g_seed;
+
+// Simple random number generator. Using this instead of rand()
+// for cross platform determinism.
+inline int RandomInt()
+{
+	// XorShift32 algorithm
+	uint32_t x = g_seed;
+	x ^= x << 13;
+	x ^= x >> 17;
+	x ^= x << 5;
+	g_seed = x;
+
+	// Map the 32-bit value to the range 0 to RAND_LIMIT
+	return (int)( x % ( RAND_LIMIT + 1 ) );
+}
 
-/// Random integer in range [lo, hi)
+// Random integer in range [lo, hi]
 inline float RandomInt( int lo, int hi )
 {
-	return lo + rand() % ( hi - lo );
+	return lo + RandomInt() % ( hi - lo + 1 );
 }
 
-/// Random number in range [-1,1]
+// Random number in range [-1,1]
 inline float RandomFloat()
 {
-	float r = (float)( rand() & ( RAND_LIMIT ) );
+	float r = (float)( RandomInt() & ( RAND_LIMIT ) );
 	r /= RAND_LIMIT;
 	r = 2.0f * r - 1.0f;
 	return r;
 }
 
-/// Random floating point number in range [lo, hi]
+// Random floating point number in range [lo, hi]
 inline float RandomFloat( float lo, float hi )
 {
-	float r = (float)( rand() & ( RAND_LIMIT ) );
+	float r = (float)( RandomInt() & ( RAND_LIMIT ) );
 	r /= RAND_LIMIT;
 	r = ( hi - lo ) * r + lo;
 	return r;
 }
 
-/// Random vector with coordinates in range [lo, hi]
+// Random vector with coordinates in range [lo, hi]
 inline b2Vec2 RandomVec2( float lo, float hi )
 {
 	b2Vec2 v;

samples/sample_benchmark.cpp

@@ -74,7 +74,7 @@ class BenchmarkBarrel : public Sample
 
 	void CreateScene()
 	{
-		srand( 42 );
+		g_seed = 42;
 
 		for ( int i = 0; i < e_maxRows * e_maxColumns; ++i )
 		{

src/CMakeLists.txt

@@ -155,7 +155,7 @@ elseif (MINGW)
 	endif()
 elseif (APPLE)
 	message(STATUS "Box2D on Apple")
-	target_compile_options(box2d PRIVATE -ffp-model=precise -ffp-contract=off)
+	target_compile_options(box2d PRIVATE -ffp-contract=off)
 elseif (EMSCRIPTEN)
 	message(STATUS "Box2D on Emscripten")
 elseif (UNIX)

src/shape.c

@@ -22,11 +22,6 @@ static b2Shape* b2GetShape( b2World* world, b2ShapeId shapeId )
 	return shape;
 }
 
-b2Transform b2GetOwnerTransform( b2World* world, b2Shape* shape )
-{
-	return b2GetBodyTransform( world, shape->bodyId );
-}
-
 static b2ChainShape* b2GetChainShape( b2World* world, b2ChainId chainId )
 {
 	int id = chainId.index1 - 1;
@@ -766,7 +761,7 @@ bool b2Shape_TestPoint( b2ShapeId shapeId, b2Vec2 point )
 	b2World* world = b2GetWorld( shapeId.world0 );
 	b2Shape* shape = b2GetShape( world, shapeId );
 
-	b2Transform transform = b2GetOwnerTransform( world, shape );
+	b2Transform transform = b2GetBodyTransform( world, shape->bodyId );
 	b2Vec2 localPoint = b2InvTransformPoint( transform, point );
 
 	switch ( shape->type )
@@ -785,40 +780,41 @@ bool b2Shape_TestPoint( b2ShapeId shapeId, b2Vec2 point )
 	}
 }
 
-b2CastOutput b2Shape_RayCast( b2ShapeId shapeId, b2Vec2 origin, b2Vec2 translation )
+// todo_erin untested
+b2CastOutput b2Shape_RayCast( b2ShapeId shapeId, const b2RayCastInput* input )
 {
 	b2World* world = b2GetWorld( shapeId.world0 );
 	b2Shape* shape = b2GetShape( world, shapeId );
 
-	b2Transform transform = b2GetOwnerTransform( world, shape );
+	b2Transform transform = b2GetBodyTransform( world, shape->bodyId );
 
 	// input in local coordinates
-	b2RayCastInput input;
-	input.maxFraction = 1.0f;
-	input.origin = b2InvTransformPoint( transform, origin );
-	input.translation = b2InvRotateVector( transform.q, translation );
+	b2RayCastInput localInput;
+	localInput.origin = b2InvTransformPoint( transform, input->origin );
+	localInput.translation = b2InvRotateVector( transform.q, input->translation );
+	localInput.maxFraction = input->maxFraction;
 
 	b2CastOutput output = { 0 };
 	switch ( shape->type )
 	{
 		case b2_capsuleShape:
-			output = b2RayCastCapsule( &input, &shape->capsule );
+			output = b2RayCastCapsule( &localInput, &shape->capsule );
 			break;
 
 		case b2_circleShape:
-			output = b2RayCastCircle( &input, &shape->circle );
+			output = b2RayCastCircle( &localInput, &shape->circle );
 			break;
 
 		case b2_segmentShape:
-			output = b2RayCastSegment( &input, &shape->segment, false );
+			output = b2RayCastSegment( &localInput, &shape->segment, false );
 			break;
 
 		case b2_polygonShape:
-			output = b2RayCastPolygon( &input, &shape->polygon );
+			output = b2RayCastPolygon( &localInput, &shape->polygon );
 			break;
 
 		case b2_chainSegmentShape:
-			output = b2RayCastSegment( &input, &shape->chainSegment.segment, true );
+			output = b2RayCastSegment( &localInput, &shape->chainSegment.segment, true );
 			break;
 
 		default:
@@ -832,6 +828,7 @@ b2CastOutput b2Shape_RayCast( b2ShapeId shapeId, b2Vec2 origin, b2Vec2 translati
 		output.normal = b2RotateVector( transform.q, output.normal );
 		output.point = b2TransformPoint( transform, output.point );
 	}
+
 	return output;
 }
 

test/CMakeLists.txt

@@ -26,7 +26,7 @@ if (MSVC)
 	target_compile_options(test PRIVATE /experimental:c11atomics)
 elseif (APPLE)
     # determinism settings
-	target_compile_options(test PRIVATE -ffp-model=precise -ffp-contract=off)
+    target_compile_options(test PRIVATE -ffp-contract=off)
 endif()
 
 target_link_libraries(test PRIVATE box2d enkiTS)