Arpad-Your definition of "default" is very different from any other that I have ever encountered.
The operative phrase from BIRD 127.4 is "for the case when the user doesn't make that selection". I see that that phrase is limited in that for parameters with Usage Out, it's the model that makes the selection and not the user. So that phrase probably should be modified to read "for the case when the user or the model doesn't make that selection."
Your statement about Default being THE value is very surprising, in that if the Default value is THE value, then there's no reason to have the other Formats such as Range, List, etc. According to your statement, these formats would be ignored, and the Default value would be used regardless. I don't see how that can make any sense.
With the possible exception of editing the phrase in BIRD 127.4, I still don't see what problem your proposed BIRD solves.
Mike S. On 12/15/2011 02:28 PM, Muranyi, Arpad wrote:
Mike, Let's clarify what the meaning of "Default" is then and review what the spec and BIRD 127.4 says about it. In BIRD 127.4 we say that - Default and Value are mutually exclusive, i.e. single valued parameters can only have Value <data> or Default <data> but not both. - All other types of parameters are multi valued, Range, List, etc... in which case Default is optional and is used for the purpose of "selecting" a value from all of the possibilities within the range or list, for the case when the user doesn't make that selection. In the latter case, the meaning of Default to me is not so much about what initial conditions the EDA tool should assume while it is waiting for the "real thing" to arrive. In this context, Default to me means that from all the possible values defined in the .ami file, this is THE value that should be passed on. Whether that value is supposed to be interpreted as an initial condition (or default) in the tool or not would depend on the definition, or description (semantics) of the parameter itself which is a different story. In the former case, Default and Value are treated as synonyms, but at the end it is still just a value that is passed on. My interpretation is still the same, that whether the value is supposed to be treated as an initial condition (or default) in the tool or not would depend on the definition, or description (semantics) of the parameter itself. So I think of "Default" in the .ami file as a default for the selection mechanism for multi valued parameters so that one value could be passed on whether the user makes the selection or not. I do not think of "Default" in the .ami file to mean that these values are to be treated in the EDA tool as initial conditions or defaults for Usage Out parameters whose real value will be given to the EDA tool later by the AMI model. In this context my view is that the spec does not define or even mention that Usage Out parameters are supposed to be initialized in the EDA tool using the values in the .ami file. This is the hole I see in the spec that needs to be plugged. We need to describe or define what the purpose of the <data> in the .ami file is for Usage Out parameters. It seems (even from this thread) that different people may interpret the situation differently, and I think this can cause problems down the line.Regarding "I hope we're not trying to make all tools produce the same results", yes and no.There are some basic expectations where all tools should produce the same results, but there are situations when the results may differ due to proprietary secret sauce algorithms. Here is yet another possibly stupid example, an integration. If two tools produce different results because they and/or the model maker had different assumptions on how a Usage Out parameter would initialize the integration constant, one tool might return a DC shifted waveform while the other might not. In this case I would indeed expect the two tools to give the same results with the same input parameters in the .ami file. Thanks, Arpad ========================================================================*From:*ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] *On Behalf Of *Mike Steinberger*Sent:* Thursday, December 15, 2011 1:30 PM *To:* ibis-macro@xxxxxxxxxxxxx *Subject:* [ibis-macro] Re: Usage Out syntax rules Arpad- First of all, it seems like we need a better example.Secondly, it seems that the problem we're trying to solve is to make sure that models can run in all tools. That's good. However, I still don't see how differing assumptions about how to interpret the default value of an Out parameter could cause model to be unable to run in different tools.Thirdly, I hope we're not trying to make all tools produce the same results. That's outside the scope of the IBIS specification, and yet it seems to be the problem you're trying to address.Fourthly, the very definition of a default value is that it's the value to be used until another value becomes available. I believe this principle clearly applies in the circumstances you're describing, and is sufficient to completely answer the questions you're posing.Mike S. On 12/15/2011 01:05 PM, Muranyi, Arpad wrote: Mike, I did say that "It may not be the best example, but I hope it illustrates my thinking". Re "What <data> are you referring to, specifically?" I am referring to "<data>" that is described in the spec and BIRD 127.4 as "<data>", i.e. the value(s) provided for the various parameters.Re "What problem would they be trying to solve that would cause either the EDA vendor or their tool to choose some value other than the one supplied by the model developer?", this is irrelevant to this discussion.The question is about data flow between the .ami file, EDA tool, and AMI model. The spec says Usage Info data goes from the .ami file to the EDA tool, Usage Out goes from the AMI model to the EDA tool, Usage In goes from the .ami file to the AMI model, Usage InOut goes from the .ami file to the AMI model and then from the AMI model to the EDA tool. So the question remains, if the .ami file supplies <data> (values) with Usage Out, but the spec says that for Usage Out the value comes from the AMI model, what are we supposed to do with the data that is supplied in the .ami file for the Usage Out parameters? Since there are many options for what to do with that data, I expect that different EDA vendors and model makers might decide to do different things. This may result in non-portability, and non-interoperability. Re "Supposing the EDA vendor or their tool chose a value other than one supplied by the model developer and they happened to get it wrong, how does that concern IBIS?" This is not what I am talking about. I am talking about a situation when the model developer can supply two values without being able to tell the EDA tool which one to use and when. One of the values in the .ami file in the Usage Out parameter's <data> and the other value returned by the AMI model for the same Usage Out parameter. Re #3 below, I am not talking about that at all. Like I said, my example may not have been a perfect one, but you should have looked past that instead of starting to pick on its imperfection. Please try to talk about the problem, not about how my illustrations are imperfect. Thanks, Arpad ========================================================*From:*ibis-macro-bounce@xxxxxxxxxxxxx <mailto:ibis-macro-bounce@xxxxxxxxxxxxx> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] *On Behalf Of *Mike Steinberger*Sent:* Thursday, December 15, 2011 11:34 AM *To:* ibis-macro@xxxxxxxxxxxxx <mailto:ibis-macro@xxxxxxxxxxxxx> *Subject:* [ibis-macro] Re: Usage Out syntax rules Arpad-I can't see how your example represents anything that people/EDA tools are doing now, or would do to solve a plausible problem.1. Your example supposes that the EDA tool vendor (not just the EDA tool) decides to store the <data> for internal data structure initialization. What <data> are you referring to, specifically? What problem would they be trying to solve that would cause either the EDA vendor or their tool to choose some value other than the one supplied by the model developer?2. Supposing the EDA vendor or their tool chose a value other than one supplied by the model developer and they happened to get it wrong, how does that concern IBIS?3. Your example supposes that some bad thing can happen if the model supplies some value such as 0 or -1, and you give dividing by zero as an example of such a bad thing. Almost every programmer knows how to avoid dividing by zero, and most decent programmers know to validate all of the assertions their computation is based on before they attempt the computation. (Any who don't should read Jon Bentley's classic book /Programming Pearls/.) Is it IBIS' responsibility to protect less competent programmers from themselves?So far as I can tell, you've hypothesized a problem that doesn't actually exist when we have enough problems to solve which have come from real user projects.Mike S. On 12/15/2011 11:04 AM, Muranyi, Arpad wrote: Mike, Regarding "So far, you haven't provided a compelling description of one.", I thought I did. Would you please tell me what you think of this example? It may not be the best example, but I hope it illustrates my thinking: "If an EDA tool vendor decides to do what you say [opt to store the <data> for internal data structure initialization] based on their own really smart thinking, but the model's author decides that this value in the .ami file is not going to be useful for anything because the real value will come from their model, and they put a bogus number, like 0 or -1 in the .ami file, you might end up getting divide by zero errors or similar fun things if the nature of the parameter might be such that it can't handle negative numbers or zero. This is why I feel that the spec MUST say something about what the number in the .ami file is used for, or say that it should be ignored." Thanks, Arpad =====================================================*From:*ibis-macro-bounce@xxxxxxxxxxxxx <mailto:ibis-macro-bounce@xxxxxxxxxxxxx> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] *On Behalf Of *Mike Steinberger*Sent:* Thursday, December 15, 2011 8:52 AM *To:* ibis-macro@xxxxxxxxxxxxx <mailto:ibis-macro@xxxxxxxxxxxxx> *Subject:* [ibis-macro] Re: Usage Out syntax rules Arpad-I don't see that there's a problem to solve in the first place. So far, you haven't provided a compelling description of one.Let's not confuse the parameter declaration with the parameter itself. All that a .ami file contains is parameter declarations with static initializations (that is, default values). The parameter itself is what's passed in or out of the model. Any of the statically initialized parameter values in the .ami file, including those of Usage Info, can be over-written by the model, the EDA tool or the user for whatever reason they choose. (You may disagree with any decision by an EDA tool or a user to over-write a parameter value, but that's none of our business.) They are an initial value and no more.In the case of parameters of Usage Out, any initial value almost certainly will be over-written by the model itself. There's no question about where the value comes from. If the model outputs the parameter, as promised in the .ami file, then the parameter's initial value will be over-written, and can be ignored. If the model does not output the parameter even though it was declared in the .ami file, then that's an obvious error that the model developer should correct, and will correct if the users demand it.Statically initialized variable declarations exist in many programming languages, most notably C. We're using these declarations in exactly the same way in IBIS-AMI as they are used in all the other programming languages. They don't have a problem and, as far as I can tell, neither do we.Mike S. On 12/14/2011 11:13 PM, Muranyi, Arpad wrote: Bob, Let's distinguish between two things in this discussion. #1) The technical solution that this BIRD draft proposes, #2) The question whether there is a problem in the existing spec and the existing BIRDs For the first one, I am not saying that this is the only way to solve the problem. In fact, if you look at the first message (on the bottom), you will see that I was originally considering several approaches in the form of questions. I wrote the BIRD draft as it stands based on one private feedback, which seems to be the simplest approach. But I am open for suggestions, and I really don't care how we solve the problem, as long as we solve it. For the second one, we need to agree on whether there is a problem or not. Correct me if I am wrong, but as far as I can tell, we have a logic conflict in the spec. It's as if we had two outputs driving one input without a selector. One output is the Usage Out parameter in the .ami file (providing a value for the EDA tool -- but I am not even sure to whom this value is provided) and the other output is the model which is also sending a value to the EDA tool. How do you propose to resolve this conflict without saying anything about which one to use and under what conditions? Currently the spec doesn't say anything about that. In addition, if the purpose of these duplicate values is to define an initial condition, how would an EDA vendor know whether they should use the value in the .ami file to initialize themselves, or the model? Recall, the parameters in the .ami file go to the tool if they are Info, or the model if they are In, but where do they go from the .ami file if they are Out? We know if they are Out, they go from the model to the tool, but where does the <data> supposed to go from the .ami file? This is simply not defined in the spec. Maybe a better circuit equivalent of this situation is a driver without being connected to anything. Why is it there then? Some may assume it is there for this reason, others may assume it is there for another reason, and incompatibility and non-portability will set in very quickly... As I stated it before, I am open to suggestions, I don't feel that we have to solve the problem the way this draft proposes it, but I think we do need to something about it. I don't even mind leaving the general syntax as is, but then I will demand that each parameter that is defined as Usage Out should spell out the rules on these questions, so there would be no ambiguities left in the spec. (This would lead to a lot of repetition in the spec, though, so I think we would be wiser to modify the general syntax). Now, some specific answers to your email. Regarding "It should NOT be confused or misread as a syntax statement that <data> is optional for some <data_format> cases in an .ami file.", I didn't make that suggestion in this BIRD draft. (I did consider it in the email on the bottom, but didn't put it into the BIRD draft). Regarding "In fact, an EDA tool might opt to store the <data> for internal data structure initialization.", this is exactly the case in point. If an EDA tool vendor decides to do what you say based on their own really smart thinking, but the model's author decides that this value in the .ami file is not going to be useful for anything because the real value will come from their model, and they put a bogus number, like 0 or -1 in the .ami file, you might end up getting divide by zero errors or similar fun things if the nature of the parameter might be such that it can't handle negative numbers or zero. This is why I feel that the spec MUST say something about what the number in the .ami file is used for, or say that it should be ignored. Regarding "Rule 7 adds a new restriction it is a syntactical violation for Default to be used at all for Usage Out parameters.", why is this a violation? The rule with this new addition is that it is not allowed for Usage Out parameters, and optional for all others, and it is not allowed together with Value. Prohibiting Default in Usage Out Value doesn't conflict with anything, it is prohibited for two reasons, one because it is Value, and second because it is Usage Out. I don't see any violations, am I missing something? Regarding "Also, since and optional Default overrides <typ> in some cases and is used in place of Value for other parameters, nothing is gained be adding the new syntax restriction.", consider this: <typ> is part of <data>. If <data> is ignored by my new rule, <typ> is ignored too. What is the interpretation of Default, if it is allowed? Is it supposed to be in effect, so that the ignored <data> is substituted with its value? If this was the case, we would be back to square one, because the whole purpose of this BIRD was to make <data> ineffective for Usage Out parameters to remove the ambiguities they introduce. If this is what we want to achieve with this BIRD, shouldn't Default also be either ignored, or prohibited? I chose to prohibit it, since we already have a prohibition with Value, and to me it is cleaner to eliminate extra bogus data in the .ami file than allow them to be there for no other reason than to be ignored. Thanks, Arpad =================================================================== *From:*Bob Ross [mailto:bob@xxxxxxxxxxxxx] *Sent:* Wednesday, December 14, 2011 8:27 PM*To:* Muranyi, Arpad; ibis-macro@xxxxxxxxxxxxx <mailto:ibis-macro@xxxxxxxxxxxxx>*Subject:* RE: [ibis-macro] Re: Usage Out syntax rules All: I already presented some objections to Arpad, and I see no need for this BIRD. I am not convinced of any technical need, and more rules cost money in terms of more documentation, more test cases and error codes and mistakes/delays in developing a parser. ----- Rule 10 should NOT be listed under Notes because it is not a syntax rule. It should be placed elsewhere. The rule provides EDA tool guidance as to how to handle <data> in the .ami file for a Usage Out parameter. It should NOT be confused or misread as a syntax statement that <data> is optional for some <data_format> cases in an .ami file. In fact, an EDA tool might opt to store the <data> for internal data structure initialization. So it is questionable to state or require EDA tools to absolutely ignore <data> ------ Rule 7 adds a new restriction it is a syntactical violation for Default to be used at all for Usage Out parameters. For clarity, this must be stated as a separate rule to avoid mixing a set of <data_format> exceptions with Usage exceptions. Also, the full rule must also be added in one or more sections such as where Default is given and perhaps where Out is introduced. The Notes are not the primary source for a rule, but just a partial summary of restrictions noted explained elsewhere. Otherwise the documentation is internally inconsistent - a problem for the parser developer. Also, since and optional Default overrides <typ> in some cases and is used in place of Value for other parameters, nothing is gained be adding the new syntax restriction. ------- So I do not see the value or need for this proposal. Bob*From:*ibis-macro-bounce@xxxxxxxxxxxxx <mailto:ibis-macro-bounce@xxxxxxxxxxxxx> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] <mailto:[mailto:ibis-macro-bounce@xxxxxxxxxxxxx]> *On Behalf Of *Muranyi, Arpad*Sent:* Wednesday, December 14, 2011 3:40 PM *To:* ibis-macro@xxxxxxxxxxxxx <mailto:ibis-macro@xxxxxxxxxxxxx> *Subject:* [ibis-macro] Re: Usage Out syntax rules Hello, I took the initiative and wrote a new BIRD draft to address the issues I brought up in the email below. (See attached file). The way this BIRD is written doesn't change any of the .ami file syntax, i.e. Usage Out parameters are still required to contain <data>, but the BIRD states that this data is ignored. The other new rule I added was to prohibit Default when the Usage is Out, since the <data> is coming from the model, and I don't see why we should pay attention to Default in the .ami file when <data> is ignored anyway. Please take a few minutes to review it and send me your questions, comments, suggestions if you have any. I would hope that this simple BIRD would not take up much of our time, and could be submitted to the Open Forum in a short time. Thanks, Arpad ========================================================*From:*ibis-macro-bounce@xxxxxxxxxxxxx <mailto:ibis-macro-bounce@xxxxxxxxxxxxx> [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] <mailto:[mailto:ibis-macro-bounce@xxxxxxxxxxxxx]> *On Behalf Of *Muranyi, Arpad*Sent:* Monday, December 12, 2011 5:38 PM *To:* ibis-macro@xxxxxxxxxxxxx <mailto:ibis-macro@xxxxxxxxxxxxx> *Subject:* [ibis-macro] Usage Out syntax rules All, I looked at BIRD 127.4 again to see what the options might be to say something about Usage Out parameters. I double checked, and this text applies to all parameters, Reserved and Model_Specific: |* All parameters must be in the following format: |* |* (parameter_name (Usage <usage>) |* (Type <data_type>) |* ({Format} <data_format> <data>) |* (Default <value>) |* (Description <string>)) There is another rule that Default and Format Value can't coexist in the same parameter. All other Formats are allowed to have Default. We could possibly refine/revise the notes below this syntax definition. Here are the relevant notes which could be considered: |* 4) The <data_format> selection of Value and Default are|* always mutually exclusive. Certain parameters may require|* Value or Default, but Value and Default are not allowed to|* be present together for the same parameter. |* 5) <data_format> is always required for selections other |* than Value.|* 6) Default is optional for <data_format> Range, List, Corner,|* Increment and Steps.|* 7) Default is not allowed for <data_format> Table, Gaussian,|* Dual-Dirac and DjRj. We should probably state that for Usage Out, -Default is not allowed -Format Value is not allowed -and <data> shall be omitted for all other <data_format>s. Table poses an interesting exception. According to BIRD 132, tables of Usage Out are still required to contain a single row of data, so that the tool would know how many columns are in a row when it reads the flattened data coming from the model. Questions, comments, suggestions are welcome. Thanks, Arpad ================================================================