Todd/All, I think Arpad's Summary comments (a to e below) are very valid and timely. The purpose here is not to bash the AMI standard, but to complete it and make sure it is respected technically and adopted. Can we address these points please? They all seem common sense, which usually works for me. Regards, Richard PS Although I've replied to the "garbage collection" thread, I didn't view this as an issue - just a necessary coding step. ________________________________ From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of vuk_borich@xxxxxxxxxxx Sent: 02 April 2008 09:05 To: twesterh@xxxxxxxxxx; Arpad_Muranyi@xxxxxxxxxx; ibis-macro@xxxxxxxxxxxxx Subject: [ibis-macro] Re: IBIS-AMI Correlation and BIRD Update - comments Hi Todd, We are all aware that "garbage collection" is a well-known software concept used extensively in managed code frameworks like .NET and Java, and that Arpad's paper uses it in that context, not as his personal view of any vendor's coding style. Is my understanding correct? Vuk From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Todd Westerhoff Sent: Wednesday, April 02, 2008 8:54 AM To: Arpad_Muranyi@xxxxxxxxxx; 'IBIS-ATM' Subject: [ibis-macro] Re: IBIS-AMI Correlation and BIRD Update - comments Arpad, If I were to come up with a high level summary of your concerns, it would include: - use of persistent memory between the AMI_Init and AMI_Getwave calls - modifying time-domain waveforms in place I know I'm simplifying, but I believe that's a reasonable 10,000 foot view. Here's what we've all accomplished with IBIS-AMI - it's defined - it's approved - it works - we have working models in customer's hands Does that mean everything associated with IBIS-AMI models is simple and intuitive? Nope. Are there areas that we might do differently if we had the chance to do it all over again? Sure. Is it worth opening up an defined spec and asking vendors to change models they've already developed (again)? Probably not. I'm not trying to minimize or ignore the impact on the model developer, and I really do get that these techniques require time to understand. I'm usually the "marketing guy" in any technical conversation, and assume that if I can understand this stuff, it's accessible to others. My point is this - as we already have a standard and a infrastructure that works, so why don't we turn our attention to developing reference models that isolate the model developer from the details of the simulator interface? Isolate the impulse response and waveform filtering section of the reference models, with a *your specific filtering code goes here* approach. I think that's entirely workable within the existing specification. We don't need to rework the standard, we need to take the reference code we've published as part of the standard and build on it. I'm therefore advocating that we work to upgrade reference models and toolkits in response to your concerns. I believe this addresses the concerns you've raised without requiring anyone to rework their existing models. Which brings me to the unpleasant part. I have to take exception to phrases like: "Stuff is going in and out of the functions BEHIND the SCENES through the backdoors" "yet we are already setting the stage for doing things in a kludge way" "computer science back door trickery in order to achieve the fundamental goal of this technology" and my favorite example from your presentation at DesignCon: If you're trying to work towards an open standard, these choices of language and graphics aren't helping your case. In my personal opinion, this is consistent with what I'd expect from a vendor interested in delaying progress. I apologize for having to make what sounds like a personal accusation - I don't mean it that way ... but I am requesting that we all choose our words very carefully. This is on the record, after all. Todd. Todd Westerhoff VP, Software Products SiSoft 6 Clock Tower Place, Suite 250 Maynard, MA 01754 (978) 461-0449 x24 twesterh@xxxxxxxxxx www.sisoft.com -----Original Message----- From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad Sent: Wednesday, April 02, 2008 1:00 AM To: IBIS-ATM Subject: [ibis-macro] IBIS-AMI Correlation and BIRD Update - comments Hello IBIS-AMI experts, I want to preface this message with a "warning" to eliminate the possibilities of going off in a tangent of personal remarks, and ending up hurting each other's feelings. My intensions are NOT to end up with a blood bath, but the seriousness of the issues I want to raise could very easily take us there if we don't handle the topic in a professional way. First, I would like to comment on the presentation we saw today in the IBIS-ATM meeting. 1) I am fine up to pg. 9., but I have a little problem on pg. 9. This is really a small thing, but can be confusing considering the big picture. Based on pg. 8, I gather that the meaning of the arrow pointing to the black box from above is "this is what's inside the box". On pg. 9, however, the same notation seems to mean "this is the input to the black box". (I am saying this based on the example Tx model). As I said, this is a small detail, but the reason I mention this is because this leads me to something bigger later. 2) On pg. 10 I am missing a statement that would clarify that: h_teg(t) = h_cr(t) * h_tei(t) (where "_" stands for subscript and "*" stands for convolve), or, on the right side of the bottom half I would have used the same expression that is found on the left side of the bottom half of pg. 11 to better clarity. Again, I say this based on what I see in the example Tx model. (You actually show that equivalence on pg. 12, but pg. 12 is still misleading somewhat because it gives me the impression that all of that is inside GetWave, when in reality that top arrow is an input to GetWave). In terms of the drawing, I am missing an arrow indicating that the output of the Init box is fed into the GetWave box. I would have drawn a similar arrow that you have on pg. 11, except pointing to the GetWave box instead of the expression on the left of the bottom half. 3) I admit that these are nitpicky comments and I can understand that Todd's busy schedule may have played a major role for missing such minor details. 4) However, as I am studying the example Tx model's source code, I feel compelled to bring up a serious concern I have regarding the coding style which may have an effect on this BIRD (and the specification). You may say, who am I to complain about coding style when I made such a fool of myself (somewhat deliberately) in my last DesignCon presentation, pretending that I don't know a thing about C programming... Please be patient and try to hear me out despite of that. Here is my understanding of the structure of the example Tx model: Init: ===== - the impulse response is passed to Init via a pointer variable along with several other parameters, including the filter tap coefficients - the code convolves the impulse response with the tap coefficients and returns the results "in place", i.e. in the same memory location where the impulse response came in - in preparation for the convolution in GetWave, an integration is performed on the equalized impulse response to obtain a step response. One could argue that this code would really belong in the GetWave function, but I can see it being here too, since it is related to the impulse response in some ways. - NOTE: this step response is NOT returned in any of the function arguments to the caller. It is just left in memory for GetWave assuming that no garbage collection is happening until we are done with GetWave. GetWave: ======== - the stimulus waveform is passed to GetWave via a pointer variable along with some other parameters - the output of Init that was left in memory is used AS THE SECOND INPUT to the convolution algorithm. This second input is not passed into the function as a function argument "normally" as the other inputs are. - additional code takes care of the block by block execution of this function using the same technique of leaving things in memory to pass left overs from a previous run as input for the next run. - the result is returned "in place", i.e. in the same memory location where the stimulus waveform came in. What bothers me the most about this example Tx model is that not all of the input and output arguments are passed through the function call interface. Stuff is going in and out of the functions BEHIND the SCENES through the backdoors! Don't take me wrong, I think this is a wonderful and clever engineering marvel for situations when there is no other way to achieve things, hats off to whoever developed it. But we are defining a new specification, we have all the freedom to do it right, yet we are already setting the stage for doing things in a kludge way. As far as I am concerned, each function should have all of their inputs and outputs go through the function arguments (and returns). I don't think this would have to result in memory penalty (due to duplication of data when calling or exiting the functions) if pointers are used appropriately. Even for the block by block repetitive execution of GetWave, I could see mechanisms for passing and returning the "left overs" around the boundaries between the calls. Something similar to "carry out" and "borrow" could be implemented on the function calls for that, but I could see even better ways of doing that without having to write any code in the GetWave function itself (to reduce the burden of the model maker). 5) Now, we could argue that this is just a coding style problem, we could fix it by writing a better example Tx model. Unfortunately not so. The reason being that Section 10 of the BIRD describes each function with a precise list and description for each argument. There are no provisions there to pass two inputs to GetWave as it may be necessary if we use the SiSoft interpretation of how data flows. There are no provisions there to do a "carry out" and "borrow" for running the GetWave multiple times for block by block execution either. But even more, pg. 18 of today's presentation proposes a new parameter associated with GetWave: "Use_Init_Output". How would the caller of GetWave pass in the output of Init without an additional function argument for the second input? This is only possible through the backdoor technique I described above! 6) I think we should have a spec with a function interface which provides all of the necessary inputs and outputs, so that model makers would not need to resort to computer science back door trickery in order to achieve the fundamental goal of this technology. A properly designed function interface would also make the use of other languages easier, because the function interfaces are much more similar between the languages than the backdoor capabilities. I firmly believe that correcting these issues would make the life of the model maker much easier. People usually understand function calls much more readily than back door tricks which rely on memory management features of a specific language. These types of things are invented by experienced programmers, not electronic engineers... In summary: =========== I would like to take this opportunity to clean up a little bit as follows: a) Each function should have all of its arguments on the function interface b) Each function should be an independent function on its own, i.e. one function should not depend on memory allocations in the other, other than using pointer variables in the argument. c) The functions should not rely on stuff left in memory, i.e. no back door data exchange should be allowed between functions (unless someone is a hacker, just kidding). d) The caller of the functions should take care of passing arguments around from one function's output to another function's input. e) The caller of the GetWave function should take care of breaking up larger data blocks into smaller pieces and executing GetWave repetitively without relying on any code related to this in the GetWave function itself. There may be more (or less), but I hope you all get the point. I hope this will not result in a bunch of virtual rotten eggs and tomatoes thrown at me... Thanks, Arpad =================================================================== --------------------------------------------------------------------- IBIS Macro website : http://www.eda.org/pub/ibis/macromodel_wip/ IBIS Macro reflector: //www.freelists.org/list/ibis-macro To unsubscribe send an email: To: ibis-macro-request@xxxxxxxxxxxxx Subject: unsubscribe