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Fixed formating, created patch file.

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Chris Boesch 2024-11-07 15:01:59 +01:00
parent 46e8fc0b61
commit bfed660020
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2 changed files with 25 additions and 25 deletions
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42
exercises/109_vectors.zig
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@ -10,16 +10,16 @@
// These are known as "single instruction, multiple data" (SIMD)
// instructions. SIMD instructions can make code significantly
// more performant.
//
//
// To see why, imagine we have a program in which we take the
// square root of four (changing) f32 floats.
//
//
// A simple compiler would take the program and produce machine code
// which calculates each square root sequentially. Most registers on
// modern CPUs have 64 bits, so we could imagine that each float moves
// into a 64-bit register, and the following happens four times:
//
// 32 bits 32 bits
// 32 bits 32 bits
// +-------------------+
// register | 0 | x |
// +-------------------+
@ -35,7 +35,7 @@
// Notice that half of the register contains blank data to which
// nothing happened. What a waste! What if we were able to use
// that space instead? This is the idea at the core of SIMD.
//
//
// Most modern CPUs contain specialized registers with at least 128 bits
// for performing SIMD instructions. On a machine with 128-bit SIMD
// registers, a smart compiler would probably NOT issue four sqrt
@ -50,11 +50,11 @@
// +---------------------------------------+
// register | 4.0 | 9.0 | 25.0 | 49.0 |
// +---------------------------------------+
//
//
// |
// [SIMD SQRT instruction]
// V
//
//
// +---------------------------------------+
// register | 2.0 | 3.0 | 5.0 | 7.0 |
// +---------------------------------------+
@ -74,26 +74,26 @@
// SIMD instructions, whenever possible.
//
// Defining vectors in Zig is straightforwards. No library import is needed.
const v1 = @Vector(3, i32) { 1, 10, 100};
const v2 = @Vector(3, f32) {2.0, 3.0, 5.0};
const v1 = @Vector(3, i32){ 1, 10, 100 };
const v2 = @Vector(3, f32){ 2.0, 3.0, 5.0 };
// Vectors support the same builtin operators as their underlying base types.
const v3 = v1 + v1; // { 2, 20, 200};
const v4 = v2 * v2; // { 4.0, 9.0, 25.0};
// Intrinsics that apply to base types usually extend to vectors.
const v5 : @Vector(3, f32) = @floatFromInt(v3); // { 2.0, 20.0, 200.0}
const v6 = v4 - v5; // { 2.0, -11.0, -175.0}
const v7 = @abs(v6); // { 2.0, 11.0, 175.0}
const v5: @Vector(3, f32) = @floatFromInt(v3); // { 2.0, 20.0, 200.0}
const v6 = v4 - v5; // { 2.0, -11.0, -175.0}
const v7 = @abs(v6); // { 2.0, 11.0, 175.0}
// We can make constant vectors, and reduce vectors.
const v8 : @Vector(4, u8) = @splat(2); // { 2, 2, 2, 2}
const v8_sum = @reduce(.Add, v8); // 8
const v8_min = @reduce(.Min, v8); // 2
const v8: @Vector(4, u8) = @splat(2); // { 2, 2, 2, 2}
const v8_sum = @reduce(.Add, v8); // 8
const v8_min = @reduce(.Min, v8); // 2
// Fixed-length arrays can be automatically assigned to vectors (and vice-versa).
const single_digit_primes = [4] i8 {2, 3, 5, 7};
const prime_vector : @Vector(4, i8) = single_digit_primes;
const single_digit_primes = [4]i8{ 2, 3, 5, 7 };
const prime_vector: @Vector(4, i8) = single_digit_primes;
// Now let's use vectors to simplify and optimize some code!
//
@ -103,8 +103,8 @@ const prime_vector : @Vector(4, i8) = single_digit_primes;
//
// Ewa wrote the following function to figure this out.
fn calcMaxPairwiseDiffOld( list1 : [4] f32, list2 : [4] f32) f32 {
var max_diff : f32 = 0;
fn calcMaxPairwiseDiffOld(list1: [4]f32, list2: [4]f32) f32 {
var max_diff: f32 = 0;
for (list1, list2) |n1, n2| {
const abs_diff = @abs(n1 - n2);
if (abs_diff > max_diff) {
@ -120,7 +120,7 @@ fn calcMaxPairwiseDiffOld( list1 : [4] f32, list2 : [4] f32) f32 {
// Help Ewa finish the vector version! The examples above should help.
const Vec4 = @Vector(4, f32);
fn calcMaxPairwiseDiffNew( a : Vec4, b : Vec4) f32 {
fn calcMaxPairwiseDiffNew(a: Vec4, b: Vec4) f32 {
const abs_diff_vec = ???;
const max_diff = @reduce(???, abs_diff_vec);
return max_diff;
@ -138,8 +138,8 @@ const std = @import("std");
const print = std.debug.print;
pub fn main() void {
const l1 = [4] f32 { 3.141, 2.718, 0.577, 1.000};
const l2 = [4] f32 { 3.154, 2.707, 0.591, 0.993};
const l1 = [4]f32{ 3.141, 2.718, 0.577, 1.000 };
const l2 = [4]f32{ 3.154, 2.707, 0.591, 0.993 };
const mpd_old = calcMaxPairwiseDiffOld(l1, l2);
const mpd_new = calcMaxPairwiseDiffNew(l1, l2);
print("Max difference (old fn): {d: >5.3}\n", .{mpd_old});

8
patches/patches/109_vectors.patch
View file

@ -1,12 +1,12 @@
--- exercises/109_vectors.zig 2024-11-03 11:17:00.928652000 +1000
+++ answers/109_vectors.zig 2024-11-07 13:11:23.838667200 +1000
--- exercises/109_vectors.zig 2024-11-07 14:57:09.673383618 +0100
+++ answers/109_vectors.zig 2024-11-07 14:22:59.069150138 +0100
@@ -121,8 +121,8 @@
const Vec4 = @Vector(4, f32);
fn calcMaxPairwiseDiffNew( a : Vec4, b : Vec4) f32 {
fn calcMaxPairwiseDiffNew(a: Vec4, b: Vec4) f32 {
- const abs_diff_vec = ???;
- const max_diff = @reduce(???, abs_diff_vec);
+ const abs_diff_vec = @abs( a - b );
+ const abs_diff_vec = @abs(a - b);
+ const max_diff = @reduce(.Max, abs_diff_vec);
return max_diff;
}