The Init Pass by floss manual

[Codesound]

Hi,

at this page of the beautiful floss manual
http://write.flossmanuals.net/csound/a-initialization-and-performance-pass/
is write:

The Init Pass

Whenever a Csound instrument is called, all variables are set to initial values. This is called the initialization pass.

but a few paragraphs later is write:

k-Values and Initialization in Multiple Triggered Instruments

What happens on a k-variable if an instrument is called multiple times? What is the initialization value of this variable on the first call, and on the subsequent calls?

If this variable is not set explicitely, the init value in the first call of an instrument is zero, as usual. But, for the next calls, the k-variable is initialized to the value which was left when the previous instance of the same instrument turned off.

… I wondering if is correct what I have understand:

The Init Pass

Whenever a Csound instrument is called, the a and i variables are set to initial values (for the k variables see later). This is called the initialization pass.

thanks for support

R

[Karamel1]

Oh thank you! I was feeling sooo lonely not being able to understand what all this means. I hope our gurus will clarify this.

[Codesound]

@Karamel1 … you are one most active in this forum… I’m not a guru in Csound but in this forum I have had a lot of support from users. I downloaded your sample player and I try it in this week end. thanks for sharing it.

Just to reason:

Time ago Iain wrote:

Tables: ftgen and score function

Looking at the line:aline line 0, 1, 1024After 1 second aline is 1024, but if the note extends beyond 1 second line will continue in the direction in which it is going. After 2 seconds aline will be 2048 and so on.If you swap the line opcode for linseg, linseg will hold its final value rather than continue.Also the table pointer should go as far as 1023 not 1024; 0 is the 1st table value, 1023 is the 1024th table value so “aline linseg 0, 1, 1023” should fix it.

So, I just think what to say:

Whenever a Csound instrument is called, the a and i variables are set to initial values (for the k variables see later). This is called the initialization pass.

is correct…

R

[rorywalsh]

Super quick summary:

• Every time an instrument is triggered to perform it will run an initial init-pass, followed by a succession of k-passes. There will be sr/ksmps k-cycles each second.
• All variables get set to an initial value during the init pass, even k-rate variables.
• After the init pass only k and a variables can be updated.
• To find the initial value of a k-rate variable during the init pass cast the variable to i(), i.e, print i(Kvar)

Testing the values of variables:
If you wish to test variables during the init pass, test i-rate variables or cast your k variable to i-rate (see above). if-statements testing k-rate variables are only effective during k-cycles, i.e, all cycles after the init pass. For example, this instrument will print hello the first time it is run:

instr 1
   k1 init 10
   if k1 == 0 then
	   prints "Hello"
   endif
endin

It looks like the value of k1 is set to 10, yet the test returns true when asked if k1 is equal to 0. k1 is indeed set to 10, but the k-rate test will fail during the init pass and result in fall-through. However, if we test i(k1), it won’t print “Hello”, because the initial value of k1 is set to 10.

Sorry I don’t have time to go into much more details. Feel free to query any of this. It’s really a subject of much confusion for anyone starting Csound!

[Karamel1]

Hello,

Just one thing I don’t pick up. If i variables are set and are not update, how is it possible to have a loop using a i variable a a counter ? Or does it mean that the loop is done at init time only ?

This drives me to a difficulty I encounter :
Here is a instrument aiming at setting up random values to sliders which works great when called by

event “i”,3,0,0,10 ; P4 correspond to the set of sliders

> instr 3 
> reinit SET1	
> 	SET1:
> 	iCnt init 1 
> 	iRnd init 0
> 	iCnt =1 
> rireturn
> 	iCnt = 1
> 	while iCnt <=32 do 				;pour chaque pas
> 		iRnd random 0,5			; random between 0 and 4
> 		if int(iRnd) >=4 then 		; consider only when rand is >= 3 to allow more silences 
> 			iRnd random 0,127			; une velocite aleatoire
> 			Schan	sprintf	"S%d_%d",p4,iCnt
> 	 		chnset int(iRnd), Schan
> 			Schan = ""
> 		endif
> 		iCnt+=1
> 	od
> endin

Now when the same code is turned into an UDO… it does not work at all

opcode RandomMe,0,i
xin instNum
…
Schan sprintf “S%d_%d”,instNum,iCnt
…
endop

Could some one explain me why ? (I suppose this is related to initialisation)

thank you for help

[rorywalsh]

Or does it mean that the loop is done at init time only ?

Yeah. You can loop during the init pass. There is no problem there. And your i-variable values can be changed during the init pass, but once the init pass is complete, their values are fixed for the duration of that event.

Here is a instrument aiming at setting up random values to sliders which works great when called by

Why are you using reinit here? I don’t think it is necessary considering all your code is running in the init pass.

Now when the same code is turned into an UDO… it does not work at all

Can you post the UDO code?

[Karamel1]

Here it is : 2 UDO (first one “ResetInstr” works) but random one does not

opcode ResetInst, 0,k
kInstrNum    xin 
reinit SET1	
	SET1:
		indx1	=	1
	rireturn
	indx1	=	1
	Loop0:
		printf_i "    %d\n",indx1,i( kInstrNum)
		Schan	sprintf	"S%d_%d",i(kInstrNum),indx1
	 	chnset 0, Schan		
	loop_le indx1,1,32,Loop0
endop

opcode RandomJM,0,i 
iInstNum 	 xin 

reinit SET1	
	SET1:
	iCnt init 1 
	iRnd init 0
	iCnt =1 
rireturn
;ResetInst iInstNum 
	iCnt = 1
	while iCnt <=32 do 				;pour chaque pas
		iRnd random 0,5			; random between 0 and 4
		if int(iRnd) >=4 then 		; consider only when rand is >= 3 to allow more silences 
			iRnd random 0,127			; une velocite aleatoire
			Schan	sprintf	"S%d_%d", iInstNum 	,iCnt
	 		chnset int(iRnd), Schan
			Schan = ""
		endif
		iCnt+=1
	od	
endop

[rorywalsh]

You don’t need the reinit constructs at all.

opcode RandomJM,0,i 
iInstNum 	 xin 

iCnt init 1 
iRnd init 0
iCnt =1 

	iCnt = 1
	while iCnt <=32 do 				;pour chaque pas
		iRnd random 0,5			; random between 0 and 4
		if int(iRnd) >=4 then 		; consider only when rand is >= 3 to allow more silences 
			iRnd random 0,127			; une velocite aleatoire
			Schan	sprintf	"S%d_%d", iInstNum 	,iCnt
	 		prints Schan
	                ;chnset int(iRnd), Schan
			Schan = ""
		endif
		iCnt+=1
	od	
endop

Note that I removed the chnset and replaced it with an i-rate prints opcode. It prints out everything I would expect during the initial init pass.