Add parallel-letter-frequency

Author: ahans

config.json

@@ -60,10 +60,12 @@
         "prerequisites": []
       },
       {
-        "uuid": "88baa5ab-dacb-4fab-8f16-4f3ed726b27b",
         "slug": "freelancer-rates",
         "name": "Freelancer Rates",
-        "concepts": ["numbers"],
+        "uuid": "88baa5ab-dacb-4fab-8f16-4f3ed726b27b",
+        "concepts": [
+          "numbers"
+        ],
         "prerequisites": [
           "basics",
           "includes"
@@ -950,7 +952,7 @@
         "name": "Darts",
         "uuid": "e8ad3859-9999-4a36-900d-d82fa6e74b08",
         "practices": [
-          "if-statements"         
+          "if-statements"
         ],
         "prerequisites": [
           "numbers"
@@ -1018,9 +1020,7 @@
         "prerequisites": [
           "classes"
         ],
-        "difficulty": 4,
-        "topics": [
-        ]
+        "difficulty": 4
       },
       {
         "slug": "eliuds-eggs",
@@ -1033,30 +1033,23 @@
           "if-statements",
           "comparisons"
         ],
-        "difficulty": 3,
-        "topics": [
-        ]
+        "difficulty": 3
       },
       {
         "slug": "diamond",
         "name": "Diamond",
         "uuid": "f8298f68-ef4e-41e1-99af-85a1bef71561",
-        "practices": [
-        ],
-        "prerequisites": [
-        ],
-        "difficulty": 3,
-        "topics": [
-        ]
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
       },
       {
         "slug": "run-length-encoding",
         "name": "Run-Length Encoding",
         "uuid": "916fedd1-a9ed-4200-b115-cc1d1bc44aba",
         "practices": [],
         "prerequisites": [],
-        "difficulty": 3,
-        "topics": []
+        "difficulty": 3
       },
       {
         "slug": "rotational-cipher",
@@ -1068,44 +1061,39 @@
         "prerequisites": [
           "loops"
         ],
-        "difficulty": 3,
-        "topics": []
+        "difficulty": 3
       },
       {
         "slug": "resistor-color",
         "name": "Resistor Color",
         "uuid": "15a9277e-59e2-484a-9877-64437556825c",
         "practices": [],
         "prerequisites": [],
-        "difficulty": 2,
-        "topics": []
+        "difficulty": 2
       },
       {
         "slug": "resistor-color-duo",
         "name": "Resistor Color Duo",
         "uuid": "83ce95e9-f8af-4dbb-b96b-d94b12421d77",
         "practices": [],
         "prerequisites": [],
-        "difficulty": 3,
-        "topics": []
+        "difficulty": 3
       },
       {
         "slug": "minesweeper",
         "name": "Minesweeper",
         "uuid": "3753a72a-78b7-429f-b79a-f68d55a00387",
         "practices": [],
         "prerequisites": [],
-        "difficulty": 5,
-        "topics": []
+        "difficulty": 5
       },
       {
         "slug": "sublist",
         "name": "Sublist",
         "uuid": "801cb315-91d6-48e6-92f4-36423a89d4e1",
         "practices": [],
         "prerequisites": [],
-        "difficulty": 5,
-        "topics": []
+        "difficulty": 5
       },
       {
         "slug": "knapsack",
@@ -1122,8 +1110,15 @@
         "uuid": "83c92b7f-fb0e-43d8-ab7d-d514408b8575",
         "practices": [],
         "prerequisites": [],
-        "difficulty": 7,
-        "topics": []
+        "difficulty": 7
+      },
+      {
+        "slug": "parallel-letter-frequency",
+        "name": "Parallel Letter Frequency",
+        "uuid": "0a029212-bc55-4559-b3c6-2c26bec0d560",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 6
       }
     ],
     "foregone": [
@@ -1214,47 +1209,47 @@
   ],
   "key_features": [
     {
-      "icon": "fast",
       "title": "Fast execution speed",
-      "content": "With execution speed in mind, C++ is used in a wide range of computation-intensive domains."
+      "content": "With execution speed in mind, C++ is used in a wide range of computation-intensive domains.",
+      "icon": "fast"
     },
     {
-      "icon": "multi-paradigm",
       "title": "Multi-paradigm",
-      "content": "C++ supports a variety of programming paradigms like OOP, functional and procedural programming."
+      "content": "C++ supports a variety of programming paradigms like OOP, functional and procedural programming.",
+      "icon": "multi-paradigm"
     },
     {
-      "icon": "powerful",
       "title": "High-level programming",
-      "content": "C++ standardizes a comprehensive library, enabling the developer to concentrate on the problem."
+      "content": "C++ standardizes a comprehensive library, enabling the developer to concentrate on the problem.",
+      "icon": "powerful"
     },
     {
-      "icon": "homoiconic",
       "title": "Low-level programming",
-      "content": "C++ masters the strength of its predecessor C and gives the developer access to the bits and bytes."
+      "content": "C++ masters the strength of its predecessor C and gives the developer access to the bits and bytes.",
+      "icon": "homoiconic"
     },
     {
-      "icon": "widely-used",
       "title": "Popular",
-      "content": "Thanks to the flexibility and portability, you can find applications written in C++ in every scale."
+      "content": "Thanks to the flexibility and portability, you can find applications written in C++ in every scale.",
+      "icon": "widely-used"
     },
     {
-      "icon": "evolving",
       "title": "Ever-evolving",
-      "content": "Although mature, C++ is still evolving and developed by a committee to fit the developers needs."
+      "content": "Although mature, C++ is still evolving and developed by a committee to fit the developers needs.",
+      "icon": "evolving"
     }
   ],
   "tags": [
-    "paradigm/object_oriented",
-    "typing/static",
-    "typing/strong",
     "execution_mode/compiled",
+    "paradigm/object_oriented",
     "platform/android",
     "platform/ios",
     "platform/linux",
     "platform/mac",
     "platform/windows",
     "runtime/standalone_executable",
+    "typing/static",
+    "typing/strong",
     "used_for/backends",
     "used_for/cross_platform_development",
     "used_for/embedded_systems",

exercises/practice/parallel-letter-frequency/.docs/instructions.md

@@ -0,0 +1,9 @@
+# Instructions
+
+Count the frequency of letters in texts using parallel computation.
+
+Parallelism is about doing things in parallel that can also be done sequentially.
+A common example is counting the frequency of letters.
+Create a function that returns the total frequency of each letter in a list of texts and that employs parallelism.
+
+TODO: add something about C++ specifically.

exercises/practice/parallel-letter-frequency/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "ahans"
+  ],
+  "files": {
+    "solution": [
+      "parallel_letter_frequency.cpp",
+      "parallel_letter_frequency.h"
+    ],
+    "test": [
+      "parallel_letter_frequency_test.cpp"
+    ],
+    "example": [
+      "example.cpp",
+      "example.h"
+    ]
+  },
+  "blurb": "Count the frequency of letters in texts using parallel computation."
+}

exercises/practice/parallel-letter-frequency/.meta/example.cpp

@@ -0,0 +1,39 @@
+#include "parallel_letter_frequency.h"
+
+#include <algorithm>
+#include <cctype>
+#include <execution>
+
+namespace parallel_letter_frequency {
+
+namespace {
+
+[[nodiscard]] std::unordered_map<char, size_t> frequency(
+    std::string_view const text) {
+    std::unordered_map<char, size_t> freq;
+    for (auto c : text) freq[std::tolower(c)] += 1;
+    return freq;
+}
+
+}  // namespace
+
+std::unordered_map<char, size_t> frequency(
+    std::vector<std::string_view> const& texts) {
+    std::vector<std::unordered_map<char, size_t>> freqs(texts.size());
+    // determine frequencies of texts in parallel
+    std::transform(std::execution::par, texts.cbegin(), texts.cend(),
+                   freqs.begin(),
+                   [](auto const& text) { return frequency(text); });
+
+    // combine individual frequencies (this happens serially)
+    std::unordered_map<char, size_t> totals{};
+    for (auto const& single_text_freqs : freqs) {
+        for (auto const [c, count] : single_text_freqs) {
+            totals[c] += count;
+        }
+    }
+
+    return totals;
+}
+
+}  // namespace parallel_letter_frequency

exercises/practice/parallel-letter-frequency/.meta/example.h

@@ -0,0 +1,15 @@
+#if !defined(PARALLEL_LETTER_FREQUENCY_H)
+#define PARALLEL_LETTER_FREQUENCY_H
+
+#include <string_view>
+#include <unordered_map>
+#include <vector>
+
+namespace parallel_letter_frequency {
+
+[[nodiscard]] std::unordered_map<char, size_t> frequency(
+    std::vector<std::string_view> const& texts);
+
+}
+
+#endif

exercises/practice/parallel-letter-frequency/.meta/tests.toml

@@ -0,0 +1,50 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[c054d642-c1fa-4234-8007-9339f2337886]
+description = "no texts"
+
+[818031be-49dc-4675-b2f9-c4047f638a2a]
+description = "one text with one letter"
+
+[c0b81d1b-940d-4cea-9f49-8445c69c17ae]
+description = "one text with multiple letters"
+
+[708ff1e0-f14a-43fd-adb5-e76750dcf108]
+description = "two texts with one letter"
+
+[1b5c28bb-4619-4c9d-8db9-a4bb9c3bdca0]
+description = "two texts with multiple letters"
+
+[6366e2b8-b84c-4334-a047-03a00a656d63]
+description = "ignore letter casing"
+
+[92ebcbb0-9181-4421-a784-f6f5aa79f75b]
+description = "ignore whitespace"
+
+[bc5f4203-00ce-4acc-a5fa-f7b865376fd9]
+description = "ignore punctuation"
+
+[68032b8b-346b-4389-a380-e397618f6831]
+description = "ignore numbers"
+
+[aa9f97ac-3961-4af1-88e7-6efed1bfddfd]
+description = "Unicode letters"
+include = false
+
+[7b1da046-701b-41fc-813e-dcfb5ee51813]
+description = "combination of lower- and uppercase letters, punctuation and white space"
+
+[4727f020-df62-4dcf-99b2-a6e58319cb4f]
+description = "large texts"
+
+[adf8e57b-8e54-4483-b6b8-8b32c115884c]
+description = "many small texts"