32 lines
671 B
Plaintext
32 lines
671 B
Plaintext
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// polynomial for approximating erfc(x)*exp(x*x)
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//
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// Copyright (c) 2022-2023, Arm Limited.
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// SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
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deg = 15; // poly degree
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// interval bounds
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a = 0x1.0p-26;
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b = 2;
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f = proc(y) {
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return erfc(y) * exp(y*y);
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};
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approx = proc(poly, d) {
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return remez(1 - poly(x)/f(x), deg-d, [a;b], x^d/f(x), 1e-10);
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};
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poly = 0;
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for i from 0 to deg do {
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p = roundcoefficients(approx(poly,i), [|D ...|]);
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poly = poly + x^i*coeff(p,0);
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print(i);
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};
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display = hexadecimal;
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print("rel error:", accurateinfnorm(1-poly(x)/f(x), [a;b], 30));
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print("in [",a,b,"]");
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print("coeffs:");
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for i from 0 to deg do coeff(poly,i);
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