Made a tiny bit of progress today.

On a bigger machine, I was able to profile the giant unit tests module. It
has one top-level for/template that iterates over the 5 scalar types, and a
bunch of smaller ones inside that cover the multitude of operations for
each of the 4 fixed vector lengths.

profiling (lib "glm/vector/tests.rkt")
> Initial code size: 5039
> Final code size  : 1019095

The good news is, I'm seeing around 200x compression. I mean, who wouldn't
mind getting completely DRY source for as little as 1/250th the effort?
(Assuming, of course, that programming time is proportional to program size
in bytes.)

The bad news is, compilation takes around 40 seconds on a modern desktop
with plenty of CPU and RAM. From the rest of the profiling output, it looks
like phase-0 for/template is responsible for about 12.5% of the total size,
but phase-1 for/list contributes 57.2% and phase-0 check contributes 48.4%.

I'm not sure how to interpret these numbers yet. On one hand, for/template
is essentially a for/list loop unroller, so the stats could just mean it
did its job. On the other hand, I don't know how much of that 57.2% is
merely the cost of doing business in Racket.

When I comment out everything but the first two tests, I see this:

Initial code size: 243
> Final code size  : 21725

That's a mere 89x compression, which is OK because the first two tests are
relatively simple, with phase-0 for/template accounting for 58.5% of the
total size, phase-1 for/list contributing 23.2%, and no phase-0 check.

It's starting to look like there isn't much I can do to bring down the
total size. But what about total compile time?

When I manually unroll the for/template forms, the profiler gives:

Initial code size: 1509
> Final code size  : 21725

The identical final size is interesting -- it suggests the original output
sizes are what they would be if templates weren't used.

This version takes, on average, 1.883 seconds to compile. The for/template
version takes 2.499 seconds, and an empty test suite takes 1.743 seconds.
Subtracting out the control time, it took 0.612 seconds more, or 5.4x
longer, to compile a fairly simple module with for/template than without.

Is the extra cost acceptable? I'm guessing that's highly context dependent.
In this case, adding half a second to compile one module wouldn't
inconvenience me terribly, but it doesn't take much imagination to find a
situation where it would, and I have no idea how any of these numbers will


On Sat, Mar 14, 2020 at 3:28 PM Eric Griffis <> wrote:

> Alright, I re-discovered Ryan Culpepper's talk, "The Cost of Sugar," from
> the RacketCon 2018 video stream ( and
> made some progress by following along.
> Here are the .zo files larger than 100K:
> 993K ./vector/compiled/tests_rkt.zo
> 830K ./scribblings/compiled/glm_scrbl.zo
> 328K ./vector/compiled/relational_rkt.zo
> 295K ./vec4/compiled/bool_rkt.zo
> 291K ./vec4/compiled/int_rkt.zo
> 290K ./vec4/compiled/uint_rkt.zo
> 290K ./vec4/compiled/double_rkt.zo
> 289K ./vec4/compiled/float_rkt.zo
> 280K ./vec3/compiled/bool_rkt.zo
> 276K ./vec3/compiled/int_rkt.zo
> 275K ./vec3/compiled/uint_rkt.zo
> 275K ./vec3/compiled/double_rkt.zo
> 274K ./vec3/compiled/float_rkt.zo
> 262K ./vec2/compiled/bool_rkt.zo
> 258K ./vec2/compiled/uint_rkt.zo
> 258K ./vec2/compiled/int_rkt.zo
> 258K ./vec2/compiled/double_rkt.zo
> 257K ./vec2/compiled/float_rkt.zo
> 213K ./vec1/compiled/bool_rkt.zo
> 210K ./vec1/compiled/uint_rkt.zo
> 210K ./vec1/compiled/int_rkt.zo
> 210K ./vec1/compiled/double_rkt.zo
> 209K ./vec1/compiled/float_rkt.zo
> 102K ./compiled/main_rkt.zo
> 101K ./compiled/vector_rkt.zo
> I'm pretty sure that's a lot of big files. It's for a port of GLM, a
> graphics math library that implements (among other things) fixed-length
> vectors of up to 4 components over 5 distinct scalar types, for a total of
> 20 distinct type-length combinations with many small variations in their
> APIs and implementations.
> The variations I'm targeting either require a macro or exacerbate
> developer- or run-time overhead when functions are introduced. For example,
> the base component accessors for a four-component vector of doubles are:
>   dvec4-x
>   dvec4-y
>   dvec4-z
>   dvec4-w
> Each of the "xyzw" components has two aliases -- one from "rgba" and
> another from "stpq". Each accessor also has a corresponding mutator, e.g.,
> dvec4-g and set-dvec4-g!.
> For another example, whereas adding two dvec4's sums four components,
>   (dvec4
>    (fl+ (dvec4-x v1) (dvec4-x v2))
>    (fl+ (dvec4-x v1) (dvec4-x v2))
>    (fl+ (dvec4-x v1) (dvec4-x v2))
>    (fl+ (dvec4-x v1) (dvec4-x v2)))
> the same operation on dvec2's sums only the first two components.
> Furthermore, the sheer volume of the target code base makes writing
> everything out by hand a mind-numbing exercise in frustration, and that's
> when looking at a mere 20% of the pile. It's going to get much worse very
> quickly. To add fixed-length matrices up to shape 4x4 over the same scalar
> types, I'm looking at 16x5 = 80 more distinct type-shape combinations!
> Getting back to the .zo files, I had no luck running "raco macro-profiler"
> on the top end of the list. It appears to diverge. My dev laptop probably
> doesn't have enough RAM, so I'll have to try again on a bigger machine.
> Here's an excerpt from a file on the bottom end:
> [eric@walden racket-glm]$ raco macro-profiler glm/vec4/double
> profiling (lib "glm/vec4/double.rkt")
> Initial code size: 87
> Final code size  : 86531
> ========================================
> Phase 0
> the-template (defined as the-template.1 in glm/vector/template)
>   total: 31536, mean: 31536
>   direct: 2054, mean: 2054, count: 1, stddev: 0
> define-dvec4-unop (defined in "this module")
>   total: 7300, mean: 730
>   direct: 7480, mean: 748, count: 10, stddev: 0
> define/contract (defined in racket/contract/region)
>   total: 6666, mean: 44
>   direct: 3572, mean: 23, count: 153, stddev: 1.48
> define-dvec4-binop (defined in "this module")
>   total: 6200, mean: 620
>   direct: 6380, mean: 638, count: 10, stddev: 0
> ...
> Phase 1
> for/list (defined in racket/private/for)
>   total: 6558, mean: 273
>   direct: 2274, mean: 95, count: 24, stddev: 14.94
> for/fold/derived/final (defined in racket/private/for)
>   total: 4332, mean: 180
>   direct: 336, mean: 14, count: 24, stddev: 0
> for/fold/derived (defined in racket/private/for)
>   total: 4284, mean: 178
>   direct: 240, mean: 10, count: 24, stddev: 0
> for/foldX/derived (defined in racket/private/for)
>   total: 3996, mean: 24
>   direct: 3164, mean: 19, count: 170, stddev: 48.16
> Wow, does that look like nearly 1000x compression? Three orders of
> magnitude seems right, given what I know about how these macros interact.
> The "the-template" macro is defined inside a module generated by my custom
> #%module-begin. It defines 4 type-agnostic, fixed-length module templates
> (e.g., glm/vec4/template), which are instantiated once for each of the 5
> scalar types. Those fixed-length module templates are based, in turn, on
> another module template (glm/vector/template) that takes a length argument
> and uses the other profiled macros (define-dvec4-unop, define/contract,
> define-dvec4-binop) to create 20 component-wise operations per instance.
> All together, that should inflate the size of the output to somewhere near
> the middle of the interval 4x20x5x[1,4], which is 1000.
> At phase 1, the comprehension forms are busy churning out component
> aliases and unrolling component-wise operations at "compile" time. I'm
> reluctant to anti-inline these because they keep the written code small and
> the generated code fast.
> I guess the next step is to anti-inlinedefine-dvec4-unop and
> define-dvec4-binop, maybe eliminate some define/contract's, and re-profile.
> Eric
> On Friday, March 13, 2020 at 6:20:47 PM UTC-7, Eric Griffis wrote:
>> Hello,
>> I've got a package that generates (i.e., expands into) a ridiculous
>> amount of Racket code. I'd like to generate an unbelievable amount of
>> code, but things have already slowed down a lot.
>> At this point, I'm generating 20% of a massive code base and it takes
>> 4 minutes to compile (i.e., raco make) it all. If those numbers scale
>> linearly, I'm looking at 20 minutes to generate and compile the full
>> code base. Realistically, that's an optimistic lower bound.
>> How might I go about profiling something that does most of its work at
>> expansion time?
>> Should I be concerned about knocking over or clogging the package
>> repository when checking in highly "compressed" meta-programs that
>> unfurl at compile time?
>> Thanks!
>> Eric
> --
> You received this message because you are subscribed to the Google Groups
> "Racket Users" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to
> To view this discussion on the web visit
> <>
> .

You received this message because you are subscribed to the Google Groups 
"Racket Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
To view this discussion on the web visit

Reply via email to