ipa: rpi: Use std::abs()

As explained in the coding style document, usage of std::abs() is
preferred over abs() or fabs() as it picks the correct function based on
the argument type. Replace calls to abs() and fabs() with std::abs() in
the Raspberry Pi algorithms.

This fixes a reported warning from clang:

../src/ipa/rpi/controller/rpi/awb.cpp:508:6: error: using integer absolute value function 'abs' when argument is of floating point type [-Werror,-Wabsolute-value]
        if (abs(denominator) > eps) {
            ^
../src/ipa/rpi/controller/rpi/awb.cpp:508:6: note: use function 'std::abs' instead
        if (abs(denominator) > eps) {
            ^~~
            std::abs

Reported-by: Maarten Lankhorst <dev@lankhorst.se>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/ipa/rpi/controller/rpi/alsc.cpp

@@ -6,8 +6,8 @@
  */
 
 #include <algorithm>
+#include <cmath>
 #include <functional>
-#include <math.h>
 #include <numeric>
 #include <vector>
 
@@ -252,12 +252,12 @@ static bool compareModes(CameraMode const &cm0, CameraMode const &cm1)
 	 */
 	if (cm0.transform != cm1.transform)
 		return true;
-	int leftDiff = abs(cm0.cropX - cm1.cropX);
-	int topDiff = abs(cm0.cropY - cm1.cropY);
-	int rightDiff = fabs(cm0.cropX + cm0.scaleX * cm0.width -
-			     cm1.cropX - cm1.scaleX * cm1.width);
-	int bottomDiff = fabs(cm0.cropY + cm0.scaleY * cm0.height -
-			      cm1.cropY - cm1.scaleY * cm1.height);
+	int leftDiff = std::abs(cm0.cropX - cm1.cropX);
+	int topDiff = std::abs(cm0.cropY - cm1.cropY);
+	int rightDiff = std::abs(cm0.cropX + cm0.scaleX * cm0.width -
+				 cm1.cropX - cm1.scaleX * cm1.width);
+	int bottomDiff = std::abs(cm0.cropY + cm0.scaleY * cm0.height -
+				  cm1.cropY - cm1.scaleY * cm1.height);
 	/*
 	 * These thresholds are a rather arbitrary amount chosen to trigger
 	 * when carrying on with the previously calculated tables might be
@@ -732,7 +732,7 @@ static double gaussSeidel2Sor(const SparseArray<double> &M, double omega,
 	double maxDiff = 0;
 	for (i = 0; i < XY; i++) {
 		lambda[i] = oldLambda[i] + (lambda[i] - oldLambda[i]) * omega;
-		if (fabs(lambda[i] - oldLambda[i]) > fabs(maxDiff))
+		if (std::abs(lambda[i] - oldLambda[i]) > std::abs(maxDiff))
 			maxDiff = lambda[i] - oldLambda[i];
 	}
 	return maxDiff;
@@ -764,7 +764,7 @@ static void runMatrixIterations(const Array2D<double> &C,
 	constructM(C, W, M);
 	double lastMaxDiff = std::numeric_limits<double>::max();
 	for (unsigned int i = 0; i < nIter; i++) {
-		double maxDiff = fabs(gaussSeidel2Sor(M, omega, lambda, lambdaBound));
+		double maxDiff = std::abs(gaussSeidel2Sor(M, omega, lambda, lambdaBound));
 		if (maxDiff < threshold) {
 			LOG(RPiAlsc, Debug)
 				<< "Stop after " << i + 1 << " iterations";

src/ipa/rpi/controller/rpi/awb.cpp

@@ -6,6 +6,7 @@
  */
 
 #include <assert.h>
+#include <cmath>
 #include <functional>
 
 #include <libcamera/base/log.h>
@@ -505,7 +506,7 @@ static double interpolateQuadatric(ipa::Pwl::Point const &a, ipa::Pwl::Point con
 	const double eps = 1e-3;
 	ipa::Pwl::Point ca = c - a, ba = b - a;
 	double denominator = 2 * (ba.y() * ca.x() - ca.y() * ba.x());
-	if (abs(denominator) > eps) {
+	if (std::abs(denominator) > eps) {
 		double numerator = ba.y() * ca.x() * ca.x() - ca.y() * ba.x() * ba.x();
 		double result = numerator / denominator + a.x();
 		return std::max(a.x(), std::min(c.x(), result));