build.zig

@@ -1201,13 +1201,6 @@ const exercises = [_]Exercise{
         .main_file = "108_labeled_switch.zig",
         .output = "The pull request has been merged.",
     },
-    .{
-        .main_file = "109_vectors.zig",
-        .output =
-        \\Max difference (old fn): 0.014
-        \\Max difference (new fn): 0.014
-        ,
-    },
     .{
         .main_file = "999_the_end.zig",
         .output =

exercises/109_vectors.zig

@@ -1,147 +0,0 @@
-// So far in Ziglings, we've seen how for loops can be used to
-// repeat calculations across an array in several ways.
-//
-// For loops are generally great for this kind of task, but
-// sometimes they don't fully utilize the capabilities of the
-// CPU.
-//
-// Most modern CPUs can execute instructions in which SEVERAL
-// calculations are performed WITHIN registers at the SAME TIME.
-// 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
-//          +-------------------+
-// register |    0    |    x    |
-//          +-------------------+
-//
-//                    |
-//           [SQRT instruction]
-//                    V
-//
-//          +-------------------+
-//          |    0    | sqrt(x) |
-//          +-------------------+
-//
-// 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
-// instructions as above, but instead pack the floats into a single
-// 128-bit register, then execute a single "packed" sqrt
-// instruction to do ALL the square root calculations at once.
-//
-// For example:
-//
-//
-//             32 bits   32 bits   32 bits   32 bits
-//           +---------------------------------------+
-// register  |   4.0   |   9.0   |  25.0   |  49.0   |
-//           +---------------------------------------+
-//
-//                              |
-//                  [SIMD SQRT instruction]
-//                              V
-//
-//           +---------------------------------------+
-// register  |   2.0   |   3.0   |   5.0   |   7.0   |
-//           +---------------------------------------+
-//
-// Pretty cool, right?
-//
-// Code with SIMD instructions is usually more performant than code
-// without SIMD instructions. Zig cares a lot about performance,
-// so it has built-in support for SIMD! It has a data structure that
-// directly supports SIMD instructions:
-//
-//                        +-----------+
-//                        |  Vectors  |
-//                        +-----------+
-//
-// Operations performed on vectors in Zig will be done in parallel using
-// 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 };
-
-// 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}
-
-// 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
-
-// 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;
-
-// Now let's use vectors to simplify and optimize some code!
-//
-// Ewa is writing a program in which they frequently want to compare
-// two lists of four f32s. Ewa expects the lists to be similar, and
-// wants to determine the largest pairwise difference between the lists.
-//
-// Ewa wrote the following function to figure this out.
-
-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) {
-            max_diff = abs_diff;
-        }
-    }
-    return max_diff;
-}
-
-// Ewa heard about vectors in Zig, and started writing a new vector
-// version of the function, but has got stuck!
-//
-// Help Ewa finish the vector version! The examples above should help.
-
-const Vec4 = @Vector(4, f32);
-fn calcMaxPairwiseDiffNew(a: Vec4, b: Vec4) f32 {
-    const abs_diff_vec = ???;
-    const max_diff = @reduce(???, abs_diff_vec);
-    return max_diff;
-}
-
-// Quite the simplification! We could even write the function in one line
-// and it would still be readable.
-//
-// Since the entire function is now expressed in terms of vector operations,
-// the Zig compiler will easily be able to compile it down to machine code
-// which utilizes the all-powerful SIMD instructions and does a lot of the
-// computation in parallel.
-
-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 mpd_old = calcMaxPairwiseDiffOld(l1, l2);
-    const mpd_new = calcMaxPairwiseDiffNew(l1, l2);
-    print("Max difference (old fn): {d: >5.3}\n", .{mpd_old});
-    print("Max difference (new fn): {d: >5.3}\n", .{mpd_new});
-}

patches/patches/109_vectors.patch

@@ -1,13 +0,0 @@
---- 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 {
--    const abs_diff_vec = ???;
--    const max_diff = @reduce(???, abs_diff_vec);
-+    const abs_diff_vec = @abs(a - b);
-+    const max_diff = @reduce(.Max, abs_diff_vec);
-     return max_diff;
- }
-