<div dir="ltr"><div><div><div><div>Thanks Magnus. I will do as you suggest. <br><br></div>I haven't absorbed your last point yet, so this is half-baked,<br>but I can imagine using the compiler to generate executables<br>
</div>that get linked in with I/O components coming from (say) a pre-existing<br>C library, so that the repl is not involved at all. Is that a possbile <br>scenario for cakeML?<br></div><br>Cheers,<br></div>Konrad.<br><br>
</div><div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Jan 14, 2014 at 2:51 PM, Magnus Myreen <span dir="ltr"><<a href="mailto:magnus.myreen@cl.cam.ac.uk" target="_blank">magnus.myreen@cl.cam.ac.uk</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi Konrad,<br>
<div class="im"><br>
> I've downloaded cakeML from git and have been building it. I was warned<br>
> that I needed 16 GB to do everything, so I expected failure. But I wanted<br>
> to see how far it got before crashing. Here's the error message:<br>
<br>
</div>As far as I know, the full bootstrap has only been successfully run on<br>
a 64 GB machine, but maybe Ramana had some data suggesting 16 GB would<br>
is enough.<br>
<div class="im"><br>
> 294 declarations still to go<br>
> 0: (val opn_to_prim2)0 (val div_exc_cn)1 (val cdiv_exc)2 (val eq_exc_cn)3<br>
> (val ceq_exc)4 (fun pat_to_cpat*)5 (fun exp_to_cexp*)6 (datatype<br>
> call_context)7 (fun lunion)8 (val lshift)9 (fun free_vars*)10 (val<br>
> bind_fv)11 (fun label_closures*)12 (val get_label)13 (val pushret)14 (fun<br>
> compile_envref)15 (val compile_varref)16 (val el_check)17 (val<br>
> bool_to_tag)18 (val unit_tag)19 runtime: 21m34s, gctime: 21m07s,<br>
> systime: 2m40s.<br>
> 1: (val block_tag)0 (fun num_fold)1 (val push_lab)2 (val emit_ceref)3 (val<br>
> emit_ceenv)4 (val closure_tag)5 (val cons_closure)6 (val update_refptr)7<br>
> (val compile_closures)8 (val prim1_to_bc)9 (val prim2_to_bc)10 (fun<br>
> compile*)Warning - Unable to increase stack - interrupting thread<br>
> runtime: 17m06s, gctime: 16m47s, systime: 3m42s.<br>
> Exception- Interrupt raised<br>
> Holmake: Failed script build for compileReplDecsScript - exited with code 1<br>
> make: *** [all] Error 1<br>
><br>
><br>
> Questions:<br>
><br>
> 1. Is this the expected place of failure? (This is on an 8 GB box running<br>
> PolyML 5.5).<br>
<br>
</div>That looks like the expected choke point.<br>
<div class="im"><br>
> 2. I just invoked "make" in the top level. What is the invocation if I<br>
> wanted to avoid<br>
> the memory-expensive bootstrap?<br>
<br>
</div>You'll need to replace<br>
<br>
vml/bootstrap/compileReplDecsScript.sml<br>
<br>
with<br>
<br>
vml/bootstrap/compileReplDecsCheatScript.sml<br>
<br>
and also delete "Cheat" in the second line in the file, i.e. the<br>
new_theory command.<br>
<div class="im"><br>
> 2a. The build needs lem. This should be mentioned.<br>
<br>
</div>Yes, lem is required for silly Holmake reasons.<br>
<div class="im"><br>
> 2b. In lem, the hol-lib directory has a spurious file called<br>
> stringScript.sml that<br>
> derails the build. I've talked to Scott about this already.<br>
><br>
> 3. I would like to explore the verification aspects of the system. In<br>
> particular, suppose<br>
> I want to define (executable) functions in HOL and prove properties,<br>
> then somehow<br>
> map the functions to cakeML and get some sort of<br>
> "correctness-of-compilation"<br>
> theorem out that I can use to make a formal connection between the<br>
> properties, the<br>
> function, and the executable code.<br>
><br>
> For example, I define factorial and prove that it is always positive:<br>
><br>
> val fact_def = Define `fact n = if n <= 0 then 1 else n * fact (n-1)`;<br>
> (* The fact function could be over integers, if need be. *)<br>
><br>
> val fact_pos = prove(``!n. 0 < fact n``, ....);<br>
><br>
> ... and now what steps do I take? I have read the relevant papers by<br>
> Magnus and<br>
> others, but now I am seeking more concrete hints.<br>
<br>
</div>To turn your fact function into CakeML, you'll need to run it through<br>
the translator, i.e. write a file like<br>
<br>
vml/translator/ml_translator_demoScript.sml<br>
<br>
for your fact function, which can use num. The translator turns HOL<br>
``:num`` into CakeML ints and maintains an invariant that the CakeML<br>
ints are not negative.<br>
<br>
To reason about the machine code or bytecode that executes this CakeML<br>
is a bit more tricky. The top-level theorem makes a statement about<br>
the whole system in terms of an input stream of characters and an<br>
output stream of characters. I guess we'd need a verified pretty<br>
printer to turn CakeML AST into a string that is guaranteed to parse<br>
back as that CakeML AST. Alternatively, one can try to evaluate (in<br>
the logic) a the application of the parser to a string representing<br>
that AST and check that the parser maps that string into the desired<br>
AST. Then you'll need to somehow talk about your fact function in the<br>
context of all the other code that gets input during execution of the<br>
read-eval-print loop. The final theorem would be about the output<br>
string and terminate/diverge behaviour of the entire system with the<br>
fact function fed in on the input stream.<br>
<br>
I'm rather vague about the last parts because we haven't yet worked<br>
through all the details. But we aim to do so in conjunction with the<br>
verified HOL light case study.<br>
<br>
Cheers,<br>
Magnus<br>
<br>
> Thanks,<br>
> Konrad.<br>
><br>
><br>
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><br>
</blockquote></div><br></div>