gonum.org/v1/gonum v0.17.0: mat.NewDense

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify gonum.org/v1/gonum/mat.NewDense in pkg:golang/gonum.org/v1/gonum@v0.17.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/gonum.org/v1/gonum@v0.17.0
Demonstrate these symbols/APIs:
  - gonum.org/v1/gonum/mat.NewDense

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:422b700a7ffafd90c3e417ff923bce56c0c70ae8d1e3d029c45229a2ae3da0fc","contract":["mat.NewDense creates a dense matrix with the specified dimensions and backing data","mat.Dense.At retrieves matrix elements in row-major order","mat.NewDense allocates a zero-filled matrix when data is nil","mat.NewDense panics when data slice length does not match rows times columns"],"goal":"verify gonum.org/v1/gonum/mat.NewDense in pkg:golang/gonum.org/v1/gonum@v0.17.0","kind":"HOW","packages":["pkg:golang/gonum.org/v1/gonum@v0.17.0"],"schemaVersion":1,"symbols":["gonum.org/v1/gonum/mat.NewDense"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/gonum.org/v1/gonum@v0.17.0"],"schemaVersion":1,"subject":"pkg:golang/gonum.org/v1/gonum@v0.17.0","symbols":["gonum.org/v1/gonum/mat.NewDense"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require gonum.org/v1/gonum v0.17.0 // indirect

gonum.org/v1/gonum v0.17.0 h1:VbpOemQlsSMrYmn7T2OUvQ4dqxQXU+ouZFQsZOx50z4=
gonum.org/v1/gonum v0.17.0/go.mod h1:El3tOrEuMpv2UdMrbNlKEh9vd86bmQ6vqIcDwxEOc1E=

package main

import (
	"fmt"

	"gonum.org/v1/gonum/mat"
)

func main() {
	data := []float64{
		1, 2, 3,
		4, 5, 6,
	}
	m := mat.NewDense(2, 3, data)
	r, c := m.Dims()
	fmt.Printf("Matrix dimensions: %d x %d\n", r, c)
	fmt.Printf("Element (0, 1): %.2f\n", m.At(0, 1))
	fmt.Printf("Element (1, 2): %.2f\n", m.At(1, 2))
}

{
  "schemaVersion": 1,
  "goal": "verify gonum.org/v1/gonum/mat.NewDense in pkg:golang/gonum.org/v1/gonum@v0.17.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/gonum.org/v1/gonum@v0.17.0"
  ],
  "symbols": [
    "gonum.org/v1/gonum/mat.NewDense"
  ]
}

package main

import (
	"fmt"
	"math"
	"os"

	"gonum.org/v1/gonum/mat"
)

func main() {
	// Assertion 1: mat.NewDense creates a dense matrix with the specified dimensions and backing data
	data := []float64{
		1.0, 2.0, 3.0,
		4.0, 5.0, 6.0,
	}
	m := mat.NewDense(2, 3, data)
	r, c := m.Dims()
	if r != 2 || c != 3 {
		fmt.Fprintf(os.Stderr, "FAIL: mat.NewDense expected dims (2, 3), got (%d, %d)\n", r, c)
		os.Exit(1)
	}

	// Assertion 2: mat.Dense.At retrieves matrix elements in row-major order
	if val := m.At(0, 1); math.Abs(val-2.0) > 1e-9 {
		fmt.Fprintf(os.Stderr, "FAIL: mat.Dense.At(0, 1) mismatch: got %f, want 2.0\n", val)
		os.Exit(1)
	}
	if val := m.At(1, 2); math.Abs(val-6.0) > 1e-9 {
		fmt.Fprintf(os.Stderr, "FAIL: mat.Dense.At(1, 2) mismatch: got %f, want 6.0\n", val)
		os.Exit(1)
	}

	// Assertion 3: mat.NewDense allocates a zero-filled matrix when data is nil
	mZero := mat.NewDense(2, 2, nil)
	rZ, cZ := mZero.Dims()
	if rZ != 2 || cZ != 2 {
		fmt.Fprintf(os.Stderr, "FAIL: mat.NewDense nil data expected dims (2, 2), got (%d, %d)\n", rZ, cZ)
		os.Exit(1)
	}
	for i := 0; i < 2; i++ {
		for j := 0; j < 2; j++ {
			if val := mZero.At(i, j); val != 0.0 {
				fmt.Fprintf(os.Stderr, "FAIL: mat.NewDense zero matrix element at (%d, %d) mismatch: got %f, want 0.0\n", i, j, val)
				os.Exit(1)
			}
		}
	}

	// Assertion 4: mat.NewDense panics when data slice length does not match rows times columns
	panicked := false
	func() {
		defer func() {
			if r := recover(); r != nil {
				panicked = true
			}
		}()
		mat.NewDense(2, 3, []float64{1.0, 2.0, 3.0})
	}()
	if !panicked {
		fmt.Fprintf(os.Stderr, "FAIL: mat.NewDense did not panic on mismatched slice length\n")
		os.Exit(1)
	}

	fmt.Println("All gonum mat.NewDense contract assertions passed.")
}