Fix the subtraction of mean from nominators, simplify with fun_ring

src/calng/kernels/peakfinder9_gpu.cu

@@ -149,13 +149,13 @@ extern "C" __global__ void pf9(const unsigned short num_frames,
 	// whole peak should have sufficent SNR
 	float peak_weighted_row;
 	float peak_weighted_col;
-	float peak_total_mass = pixel_val - mean;
+	float peak_total_mass = 0;
 	{
 		/* TODO: more compact form */
-		float peak_weighted_row_nom = static_cast<float>(row) * pixel_val;
-		float peak_weighted_col_nom = static_cast<float>(col) * pixel_val;
+		float peak_weighted_row_nom = 0;
+		float peak_weighted_col_nom = 0;
 		const float peak_pixel_threshold = mean + min_snr_peak_pixels * sigma;
-		for (unsigned short layer=1; layer<=window_radius; ++layer) {
+		for (unsigned short layer=0; layer<=window_radius; ++layer) {
 			float total_mass_before = peak_total_mass;
 			masked_frame.fun_ring(row, col, layer, [&] (unsigned short i, unsigned short j, float val) {
 				if (val > peak_pixel_threshold) {