various minor improvements

include/mitsuba/core/atomic.h

@@ -53,7 +53,16 @@ template <typename T> inline bool atomicCompareAndExchangePtr(T **v, T *newValue
 inline bool atomicCompareAndExchange(volatile int32_t *v, int32_t newValue, int32_t oldValue) {
 #if defined(WIN32)
     return InterlockedCompareExchange(
-		reint32_terpret_cast<volatile int32_t *>(v), newValue, oldValue) == oldValue;
+		reinterpret_cast<volatile int32_t *>(v), newValue, oldValue) == oldValue;
+#else
+	return __sync_bool_compare_and_swap(v, oldValue, newValue);
+#endif
+}
+
+inline bool atomicCompareAndExchange(volatile int64_t *v, int64_t newValue, int64_t oldValue) {
+#if defined(WIN64)
+    return InterlockedCompareExchange64(
+		reinterpret_cast<volatile int64_t *>(v), newValue, oldValue) == oldValue;
 #else
 	return __sync_bool_compare_and_swap(v, oldValue, newValue);
 #endif
@@ -71,7 +80,23 @@ inline float atomicAdd(volatile float *val, float delta) {
 #endif
 		oldVal.f = *val;
 		newVal.f = oldVal.f + delta;
-	} while (atomicCompareAndExchange((volatile int32_t *) val, newVal.i, oldVal.i) != oldVal.i);
+	} while (!atomicCompareAndExchange((volatile int32_t *) val, newVal.i, oldVal.i));
+	return newVal.f;
+}
+
+inline double atomicAdd(volatile double *val, double delta) {
+	/* Atomic FP addition from PBRT */
+	union bits { double f; int64_t i; };
+	bits oldVal, newVal;
+	do {
+        // On IA64/x64, adding a PAUSE instruction in compare/exchange loops
+        // is recommended to improve performance.  (And it does!)
+#if (defined(__i386__) || defined(__amd64__))
+        __asm__ __volatile__ ("pause\n");
+#endif
+		oldVal.f = *val;
+		newVal.f = oldVal.f + delta;
+	} while (!atomicCompareAndExchange((volatile int64_t *) val, newVal.i, oldVal.i));
 	return newVal.f;
 }
 

include/mitsuba/core/kdtree.h

@@ -164,6 +164,8 @@ public:
 	inline const aabb_type &getAABB() const { return m_aabb; }
 	/// Return the depth of the constructed KD-tree
 	inline size_t getDepth() const { return m_depth; }
+	/// Return the size of the kd-tree
+	inline size_t getSize() const { return m_nodes.size(); }
 
 	/// Construct the KD-tree hierarchy
 	void build() {

include/mitsuba/core/matrix.h

@@ -261,7 +261,16 @@ public:
 		*this = temp;
 		return *this;
 	}
-	
+
+	/// Compute the trace of a square matrix
+	inline Float trace() const {
+		BOOST_STATIC_ASSERT(M == N);
+		Float sum = 0;
+		for (int i=0; i<M; ++i)
+			sum += m[i][i];
+		return sum;
+	}
+
 	/**
 	 * \brief Compute the LU decomposition of a matrix
 	 *