# 2016q3 Homework 1 (raytracing)
contributed by <`Weinux`>
###### tags: `raytracing` `Weinux`
## 開發環境
* OS：Lubuntu 15.10
* Linux系統版本: 4.2.0-42-generic
* CPU: Intel(R) Core(TM) i5-2410M CPU @ 2.30GHz
* MEM: 6GB
* Cache:
* L1d cache: 32K
* L1i cache: 32K
* L2 cache: 256K
* L3 cache: 3072K

## gprof
* gprof是個可以拿來看程式執行時，跑過哪些function和執行比率的一個實用工具。
* 從這些資訊中，我們可以觀察 到哪些function特別花時間，和被呼叫特別多次，藉由這些東西，可以針對特定function去做改善，因而得到更好的表現。
* 以raytracing-origin為例，make時得先立個flag

make PROFILE=1

* **Makefile**

EXEC = raytracing
.PHONY: all
all: $(EXEC)

CC ?= gcc
CFLAGS = \
	-std=gnu99 -Wall -O0 -g
LDFLAGS = \
	-lm

ifeq ($(strip $(PROFILE)),1)
PROF_FLAGS = -pg
CFLAGS += $(PROF_FLAGS)
LDFLAGS += $(PROF_FLAGS) 
endif

OBJS := \
	objects.o \
	raytracing.o \
	main.o

%.o: %.c
	$(CC) $(CFLAGS) -c -o $@ $<


$(EXEC): $(OBJS)
	$(CC) -o $@ $^ $(LDFLAGS)

main.o: use-models.h
use-models.h: models.inc Makefile
	@echo '#include "models.inc"' > use-models.h
	@egrep "^(light|sphere|rectangular) " models.inc | \
	    sed -e 's/^light /append_light/g' \
	        -e 's/light[0-9]/(\&&, \&lights);/g' \
	        -e 's/^sphere /append_sphere/g' \
	        -e 's/sphere[0-9]/(\&&, \&spheres);/g' \
	        -e 's/^rectangular /append_rectangular/g' \
	        -e 's/rectangular[0-9]/(\&&, \&rectangulars);/g' \
	        -e 's/ = {//g' >> use-models.h

check: $(EXEC)
	@./$(EXEC) && diff -u baseline.ppm out.ppm || (echo Fail; exit)
	@echo "Verified OK"

clean:
	$(RM) $(EXEC) $(OBJS) use-models.h \
		out.ppm gmon.out

Flat profile:

Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total           
 time   seconds   seconds    calls   s/call   s/call  name    
 20.85      0.65     0.65 56956357     0.00     0.00  subtract_vector
 15.71      1.14     0.49 69646433     0.00     0.00  dot_product
 13.79      1.57     0.43 10598450     0.00     0.00  normalize
 10.10      1.89     0.32 31410180     0.00     0.00  multiply_vector
  8.02      2.14     0.25 13861875     0.00     0.00  rayRectangularIntersection
  6.90      2.35     0.22 17836094     0.00     0.00  add_vector
  6.09      2.54     0.19  4620625     0.00     0.00  ray_hit_object
  3.53      2.65     0.11 17821809     0.00     0.00  cross_product
  2.73      2.74     0.09  4221152     0.00     0.00  multiply_vectors
  2.57      2.82     0.08  1048576     0.00     0.00  ray_color
  1.92      2.88     0.06 13861875     0.00     0.00  raySphereIntersection
  1.60      2.93     0.05  2110576     0.00     0.00  compute_specular_diffuse
  1.44      2.97     0.05  2520791     0.00     0.00  idx_stack_top
  1.28      3.01     0.04  1241598     0.00     0.00  protect_color_overflow
  0.96      3.04     0.03  2110576     0.00     0.00  localColor
  0.80      3.07     0.03  3838091     0.00     0.00  length
  0.64      3.09     0.02        1     0.02     3.12  raytracing
  0.32      3.10     0.01  1241598     0.00     0.00  refraction
  0.32      3.11     0.01  1204003     0.00     0.00  idx_stack_push
  0.32      3.12     0.01  1048576     0.00     0.00  rayConstruction
  0.16      3.12     0.01    37595     0.00     0.00  idx_stack_pop
  0.00      3.12     0.00  2558386     0.00     0.00  idx_stack_empty
  0.00      3.12     0.00  1241598     0.00     0.00  reflection
  0.00      3.12     0.00  1048576     0.00     0.00  idx_stack_init
  0.00      3.12     0.00   113297     0.00     0.00  fresnel
  0.00      3.12     0.00        3     0.00     0.00  append_rectangular
  0.00      3.12     0.00        3     0.00     0.00  append_sphere
  0.00      3.12     0.00        2     0.00     0.00  append_light
  0.00      3.12     0.00        1     0.00     0.00  calculateBasisVectors
  0.00      3.12     0.00        1     0.00     0.00  delete_light_list

./raytracing
gprof  ./raytracing | less

Raytracing結果圖

## 總結

## References