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PetriTalaComparison.kt

src/jvmMain/kotlin/afield/examples/petri/PetriTalaComparison.kt · 129 lines

package afield.examples.petri

import afield.ui.layout.D2Layout
import afield.simulation.petri.PetriLayout
import afield.simulation.petri.PetriDrawing
import afield.simulation.petri.arcCrossings
import afield.simulation.petri.PetriNet
import afield.simulation.petri.clearPetriLayoutCache
import afield.simulation.petri.frame
import afield.simulation.petri.petri
import afield.simulation.petri.toSvg
import java.io.File

FIELD_TEST id: petri.tala.comparison runner: jvm-main entrypoint: afield.examples.petri.PetriTalaComparison tags: [petri, layout, tala, d2, demo] timeoutSec: 120 expect: exitCode: 0 stdoutContains: - "petri tala comparison ok"

object PetriTalaComparison

Draws one net twice — PetriLayout.FORCE and PetriLayout.TALA — side by side, and writes the result to build/petri-tala/comparison.html.

This is the demo for native/field-d2-layout, and it is also the honest test of what that helper is for: dining philosophers is the net that made the spring model produce a hairball, so putting the two drawings next to each other is the only way to judge whether the second engine earns its keep.

It passes either way. With the helper built you get two different drawings; without it you get the same drawing twice, because TALA falls through to FORCE — and that fallback is the property worth pinning, since Field must run on a machine with no Go toolchain. What it will not tolerate is the helper being present and silently producing FORCE's answer anyway.

object PetriTalaComparison {

    private fun philosophers(count: Int = 5): PetriNet = petri {
        for (index in 0 until count) place("fork.$index", tokens = 1)
        for (index in 0 until count) {
            val right = (index + 1) % count
            place("think.$index", tokens = 1)
            place("eat.$index")
            t("take.$index") {
                from("think.$index"); from("fork.$index"); from("fork.$right"); to("eat.$index")
            }
            t("drop.$index") {
                from("eat.$index"); to("think.$index"); to("fork.$index"); to("fork.$right")
            }
        }
    }

fun main(args: Array<String>)

body — 71 lines, from line 58 
    @JvmStatic
    fun main(args: Array<String>) {
        val net = philosophers()
        val available = D2Layout.available
        println("helper: ${if (available) "present, d2 ${D2Layout.version}" else "absent — TALA will fall back"}")

        val w = 560.0
        val h = 460.0

        // Timing the two layouts once each, in order, is the obvious thing and it lies: the first
        // one pays for JVM warmup and the second does not, which on this net flattered TALA by
        // roughly a factor of ten. So both are warmed, then measured three times from a cleared
        // cache, and the minimum is reported -- the reading least polluted by whatever else the
        // machine is doing.
        fun best(layout: PetriLayout): Pair<PetriDrawing, Long> {
            var drawing = net.frame(layout)
            var bestNs = Long.MAX_VALUE
            repeat(3) {
                // BOTH caches: clearing only the Petri one leaves D2Layout's request cache warm
                // and TALA times at 0 ms, because it never reaches the subprocess.
                clearPetriLayoutCache()
                D2Layout.clearCache()
                val at = System.nanoTime()
                drawing = net.frame(layout)
                bestNs = minOf(bestNs, System.nanoTime() - at)
            }
            return drawing to bestNs / 1_000_000
        }

        val (force, forceMs) = best(PetriLayout.FORCE)
        val (tala, talaMs) = best(PetriLayout.TALA)

        val differ = net.placeNames.any { force.position(it) != tala.position(it) }

        val forceCrossings = force.arcCrossings()
        val talaCrossings = tala.arcCrossings()
        println("best of 3, warmed: FORCE ${forceMs}ms, TALA ${talaMs}ms, drawings differ: $differ")
        println("drawn arc crossings: FORCE $forceCrossings, TALA $talaCrossings")

        check(!available || differ) {
            "the helper is present but TALA reproduced FORCE exactly — it fell back silently"
        }
        check(available || !differ) {
            "the helper is absent but TALA did not fall through to FORCE"
        }

        // build/ is gitignored, so this leaves nothing behind in the tree.
        val out = File("build/petri-tala")
        out.mkdirs()
        val page = File(out, "comparison.html")
        page.writeText(
            """
            <!doctype html><meta charset="utf-8">
            <body style="margin:0;background:#0b0b0b;color:#ddd;font:13px ui-monospace,monospace">
            <div style="display:flex;gap:18px;padding:16px">
              <figure style="margin:0">
                <figcaption>FORCE — spring model, ${forceMs}ms</figcaption>
                ${force.toSvg(w, h)}
              </figure>
              <figure style="margin:0">
                <figcaption>TALA — ${if (available) "d2 ${D2Layout.version}, ${talaMs}ms" else "helper absent, fell back to FORCE"}</figcaption>
                ${tala.toSvg(w, h)}
              </figure>
            </div>
            </body>
            """.trimIndent()
        )
        println("wrote ${page.absolutePath}")
        println("petri tala comparison ok")
    }
}