ex1D10. Rejection Sampling

# ex1D10.py
# Rejection Sampling

from moduleCsound import *

tags(1)

header(nch=1)

# --- user defined opcodes

add("""
; random number generator to a given density function
; kout random number; k_minimum,k_maximum,i_fn for a density function

opcode rand_density, k, kki
kmin,kmax,ifn xin
loop:
krnd1  random  0,1
krnd2  random  0,1
k2  table  krnd1,ifn,1
  if krnd2 > k2 kgoto loop
  xout  kmin+krnd1*(kmax-kmin)
endop

; random number generator to a given probability function
; kout random number
; in: i_nr number of possible values
; i_fn1 function for random values
; i_fn2 probability functionExponential: Generate a uniformly distributed number between 0 and 1 and take its natural logarithm.

opcode rand_probability, k, iii
inr,ifn1,ifn2 xin
loop:
krnd1  random  0,inr
krnd2  random  0,1
k2  table  int(krnd1),ifn2,0
  if krnd2 > k2 kgoto loop
kout  table  krnd1,ifn1,0
  xout  kout
endop
""")

# --- instruments

add("""
instr 1
krnd  rand_density 400,800,2
aout  poscil  .1,krnd,1
  out  aout
endin

instr 2
krnd  rand_probability p4,p5,p6
aout  poscil  .1,krnd,1
  out  aout
endin
""")

tags(2)

# --- tables

add("""
;sine
f1 0 32768 10 1
;density function
f2 0 1024 6 1 112 0 800 0 112 1
;random values and their relative probability (two dice)
f3 0 16 -2 2 3 4 5 6 7 8 9 10 11 12
f4 0 16  2 1 2 3 4 5 6 5 4  3  2  1
;random values and their relative probability
f5 0 8 -2 400 500 600 800
f6 0 8  2 .3  .8  .3  .1
""")

# --- score

add("""
i1 0 10
i2 0 10 4 5 6
""")

tags(3)

writeRun(__file__)