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const std = @import("std");
const Thread = std.Thread;
const c = @cImport({
@cInclude("stdlib.h");
@cInclude("ggml/ggml.h");
});
fn is_close(a: f32, b: f32, epsilon: f32) bool {
return std.math.fabs(a - b) < epsilon;
}
pub fn main() !void {
const params = .{
.mem_size = 128*1024*1024,
.mem_buffer = null,
.no_alloc = false,
};
var opt_params = c.ggml_opt_default_params(c.GGML_OPT_LBFGS);
const nthreads = try Thread.getCpuCount();
opt_params.n_threads = @intCast(nthreads);
const NP = 1 << 12;
const NF = 1 << 8;
const ctx0 = c.ggml_init(params);
defer c.ggml_free(ctx0);
const F = c.ggml_new_tensor_2d(ctx0, c.GGML_TYPE_F32, NF, NP);
const l = c.ggml_new_tensor_1d(ctx0, c.GGML_TYPE_F32, NP);
// regularization weight
const lambda = c.ggml_new_f32(ctx0, 1e-5);
c.srand(0);
const l_data_pointer: [*]f32 = @ptrCast(@alignCast(l.*.data));
const f_data_pointer: [*]f32 = @ptrCast(@alignCast(F.*.data));
for (0..NP) |j| {
const ll = if (j < NP/2) @as(f32, 1.0) else @as(f32, -1.0);
l_data_pointer[j] = ll;
for (0..NF) |i| {
const c_rand: f32 = @floatFromInt(c.rand());
f_data_pointer[j*NF + i] =
((if (ll > 0 and i < NF/2) @as(f32, 1.0) else
if (ll < 0 and i >= NF/2) @as(f32, 1.0) else @as(f32, 0.0)) +
(c_rand/c.RAND_MAX - 0.5) * 0.1) / (0.5 * NF);
}
}
{
// initial guess
const x = c.ggml_set_f32(c.ggml_new_tensor_1d(ctx0, c.GGML_TYPE_F32, NF), 0.0);
c.ggml_set_param(ctx0, x);
// f = sum[(fj*x - l)^2]/n + lambda*|x^2|
const f =
c.ggml_add(ctx0,
c.ggml_div(ctx0,
c.ggml_sum(ctx0,
c.ggml_sqr(ctx0,
c.ggml_sub(ctx0,
c.ggml_mul_mat(ctx0, F, x),
l)
)
),
c.ggml_new_f32(ctx0, @as(f32, NP))
),
c.ggml_mul(ctx0,
c.ggml_sum(ctx0, c.ggml_sqr(ctx0, x)),
lambda)
);
const res = c.ggml_opt(null, opt_params, f);
try std.testing.expect(res == c.GGML_OPT_OK);
const x_data_pointer: [*]f32 = @ptrCast(@alignCast(x.*.data));
// print results
for (0..16) |i| {
std.debug.print("x[{d:3}] = {d:.6}\n", .{i, x_data_pointer[i]});
}
std.debug.print("...\n", .{});
for (NF - 16..NF) |i| {
std.debug.print("x[{d:3}] = {d:.6}\n", .{i, x_data_pointer[i]});
}
std.debug.print("\n", .{});
for (0..NF) |i| {
if (i < NF/2) {
try std.testing.expect(is_close(x_data_pointer[i], 1.0, 1e-2));
} else {
try std.testing.expect(is_close(x_data_pointer[i], -1.0, 1e-2));
}
}
}
_ = try std.io.getStdIn().reader().readByte();
}
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