diff options
| author | Luke Shumaker <lukeshu@lukeshu.com> | 2023-07-14 15:25:03 -0700 |
|---|---|---|
| committer | Luke Shumaker <lukeshu@lukeshu.com> | 2023-07-14 15:25:18 -0700 |
| commit | 3250a2386d3111a4ec51b37f42218c90b69ed341 (patch) | |
| tree | 32ac6edd81e791d2c3338c1f11e67f40b0cbe007 /public/make-memoize.html | |
| parent | 8c99fadac68cb05b4aaa08cab7a55c7fbfe5e364 (diff) | |
| parent | c045654a862bc1119fa4e7584fff9d2a965192ea (diff) | |
make: Add the btrfs-rec email
This isn't quite verbatim checking in the email as I did in
btrfs-progs-ng.git, I fussed with it a bit to get my blog engine to do
sane things with it.
Diffstat (limited to 'public/make-memoize.html')
| -rw-r--r-- | public/make-memoize.html | 46 |
1 files changed, 34 insertions, 12 deletions
diff --git a/public/make-memoize.html b/public/make-memoize.html index 2edb5a0..2eb5b64 100644 --- a/public/make-memoize.html +++ b/public/make-memoize.html @@ -9,16 +9,30 @@ <body> <header><a href="/">Luke Shumaker</a> » <a href=/blog>blog</a> » make-memoize</header> <article> -<h1 id="a-memoization-routine-for-gnu-make-functions">A memoization routine for GNU Make functions</h1> -<p>I’m a big fan of <a href="https://www.gnu.org/software/make/">GNU Make</a>. I’m pretty knowledgeable about it, and was pretty active on the help-make mailing list for a while. Something that many experienced make-ers know of is John Graham-Cumming’s “GNU Make Standard Library”, or <a href="http://gmsl.sourceforge.net/">GMSL</a>.</p> -<p>I don’t like to use it, as I’m capable of defining macros myself as I need them instead of pulling in a 3rd party dependency (and generally like to stay away from the kind of Makefile that would lean heavily on something like GMSL).</p> -<p>However, one really neat thing that GMSL offers is a way to memoize expensive functions (such as those that shell out). I was considering pulling in GMSL for one of my projects, almost just for the <code>memoize</code> function.</p> -<p>However, John’s <code>memoize</code> has a couple short-comings that made it unsuitable for my needs.</p> +<h1 id="a-memoization-routine-for-gnu-make-functions">A memoization +routine for GNU Make functions</h1> +<p>I’m a big fan of <a href="https://www.gnu.org/software/make/">GNU +Make</a>. I’m pretty knowledgeable about it, and was pretty active on +the help-make mailing list for a while. Something that many experienced +make-ers know of is John Graham-Cumming’s “GNU Make Standard Library”, +or <a href="http://gmsl.sourceforge.net/">GMSL</a>.</p> +<p>I don’t like to use it, as I’m capable of defining macros myself as I +need them instead of pulling in a 3rd party dependency (and generally +like to stay away from the kind of Makefile that would lean heavily on +something like GMSL).</p> +<p>However, one really neat thing that GMSL offers is a way to memoize +expensive functions (such as those that shell out). I was considering +pulling in GMSL for one of my projects, almost just for the +<code>memoize</code> function.</p> +<p>However, John’s <code>memoize</code> has a couple short-comings that +made it unsuitable for my needs.</p> <ul> <li>Only allows functions that take one argument.</li> -<li>Considers empty values to be unset; for my needs, an empty string is a valid value that should be cached.</li> +<li>Considers empty values to be unset; for my needs, an empty string is +a valid value that should be cached.</li> </ul> -<p>So, I implemented my own, more flexible memoization routine for Make.</p> +<p>So, I implemented my own, more flexible memoization routine for +Make.</p> <pre><code># This definition of `rest` is equivalent to that in GMSL rest = $(wordlist 2,$(words $1),$1) @@ -34,8 +48,13 @@ rest = $(wordlist 2,$(words $1),$1) _main = $(_$(func)_main) _hash = __memoized_$(_$(func)_hash) memoized = $(if $($(_hash)),,$(eval $(_hash) := _ $(_main)))$(call rest,$($(_hash)))</code></pre> -<p>However, I later removed it from the Makefile, as I <a href="https://projects.parabola.nu/~lukeshu/maven-dist.git/commit/?id=fec5a7281b3824cb952aa0bb76bbbaa41eaafdf9">re-implemented</a> the bits that it memoized in a more efficient way, such that memoization was no longer needed, and the whole thing was faster.</p> -<p>Later, I realized that my memoized routine could have been improved by replacing <code>func</code> with <code>$0</code>, which would simplify how the final function is declared:</p> +<p>However, I later removed it from the Makefile, as I <a +href="https://projects.parabola.nu/~lukeshu/maven-dist.git/commit/?id=fec5a7281b3824cb952aa0bb76bbbaa41eaafdf9">re-implemented</a> +the bits that it memoized in a more efficient way, such that memoization +was no longer needed, and the whole thing was faster.</p> +<p>Later, I realized that my memoized routine could have been improved +by replacing <code>func</code> with <code>$0</code>, which would +simplify how the final function is declared:</p> <pre><code># This definition of `rest` is equivalent to that in GMSL rest = $(wordlist 2,$(words $1),$1) @@ -52,10 +71,13 @@ _main = $(_$0_main) _hash = __memoized_$(_$0_hash) memoized = $(if $($(_hash)),,$(eval $(_hash) := _ $(_main)))$(call rest,$($(_hash)))</pre> <p></code></p> -<p>Now, I’m pretty sure that should work, but I have only actually tested the first version.</p> +<p>Now, I’m pretty sure that should work, but I have only actually +tested the first version.</p> <h2 id="tldr">TL;DR</h2> -<p>Avoid doing things in Make that would make you lean on complex solutions like an external memoize function.</p> -<p>However, if you do end up needing a more flexible memoize routine, I wrote one that you can use.</p> +<p>Avoid doing things in Make that would make you lean on complex +solutions like an external memoize function.</p> +<p>However, if you do end up needing a more flexible memoize routine, I +wrote one that you can use.</p> </article> <footer> |