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40 lines
1.2 KiB
WebGPU Shading Language
40 lines
1.2 KiB
WebGPU Shading Language
struct PrimeIndices {
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data: [[stride(4)]] array<u32>;
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}; // this is used as both input and output for convenience
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[[group(0), binding(0)]]
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var<storage, read_write> v_indices: PrimeIndices;
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// The Collatz Conjecture states that for any integer n:
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// If n is even, n = n/2
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// If n is odd, n = 3n+1
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// And repeat this process for each new n, you will always eventually reach 1.
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// Though the conjecture has not been proven, no counterexample has ever been found.
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// This function returns how many times this recurrence needs to be applied to reach 1.
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fn collatz_iterations(n_base: u32) -> u32{
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var n: u32 = n_base;
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var i: u32 = 0u;
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loop {
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if (n <= 1u) {
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break;
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}
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if (n % 2u == 0u) {
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n = n / 2u;
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}
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else {
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// Overflow? (i.e. 3*n + 1 > 0xffffffffu?)
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if (n >= 1431655765u) { // 0x55555555u
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return 4294967295u; // 0xffffffffu
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}
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n = 3u * n + 1u;
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}
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i = i + 1u;
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}
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return i;
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}
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[[stage(compute), workgroup_size(1)]]
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fn main([[builtin(global_invocation_id)]] global_id: vec3<u32>) {
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v_indices.data[global_id.x] = collatz_iterations(v_indices.data[global_id.x]);
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}
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