问题描述
我正在尝试使用crossbeam_utils
版本0.8.0
在二维矢量(图形)的每个位置设置值1。每个线程接收的子矩阵是不相交的。我在Windows上使用cargo run
运行代码。我的代码基于这些question1和question2。但是,出现以下错误:
thread '<unnamed>' panicked at 'index out of bounds: the len is 3 but the index is 3'
但是,如果我在产生的线程中注释命令(*slice)[row][col] = 1
,则可以看到线程在控制台中打印时工作正常。
什么原因导致此错误?
use crossbeam_utils::thread;
use std::slice;
const NTHREADS: usize = 2;
fn build_graph() -> Vec<Vec<usize>> {
let dictionary: Vec<String> = vec!["monk".to_string(),"mock".to_string(),"pock".to_string(),"pork".to_string(),"perk".to_string(),"perl".to_string()];
let s_graph = dictionary.len();
let mut graph: Vec<Vec<usize>> = vec![vec![0; s_graph]; s_graph];
let chunk = f32::ceil(s_graph as f32 / NTHREADS as f32) as usize;
let mut sliced_graph: Vec<&mut [Vec<usize>]> = Vec::with_capacity(NTHREADS);
let ptr_graph = graph.as_mut_ptr();
let mut offset;
let mut count_of_items;
// Creating mutable references for slices of the matrix
for n_th in 0..NTHREADS {
offset = n_th * chunk;
count_of_items = if offset + chunk > s_graph { s_graph - offset } else { chunk };
unsafe {
sliced_graph.push(slice::from_raw_parts_mut(ptr_graph.offset((offset) as isize),count_of_items));
}
}
thread::scope(|scope| {
let mut n_th: usize = 0;
let mut min_bound;
let mut max_bound;
for slice in &mut sliced_graph {
min_bound = n_th * chunk;
max_bound = if min_bound + chunk > s_graph { s_graph } else { min_bound + chunk};
scope.spawn(move |_| {
println!("thread number: {} - ini: {} - end: {}",n_th,min_bound,max_bound);
for row in min_bound..max_bound {
for col in 0..s_graph {
println!("th:{} -->> set row:{} col:{}",row,col);
(*slice)[row][col] = 1;
}
}
println!("thread number: {} - Finished!",n_th);
});
n_th += 1;
}
}).unwrap();
graph
}
fn main() {
build_graph();
}
解决方法
@Masklinn提出的解决方案:
use crossbeam_utils::thread;
use std::slice;
const NTHREADS: usize = 2;
fn build_graph() -> Vec<Vec<usize>> {
let dictionary: Vec<String> = vec!["monk".to_string(),"mock".to_string(),"pock".to_string(),"pork".to_string(),"perk".to_string(),"perl".to_string()];
let s_graph = dictionary.len();
let mut graph: Vec<Vec<usize>> = vec![vec![0; s_graph]; s_graph];
let chunk = f32::ceil(s_graph as f32 / NTHREADS as f32) as usize;
let mut sliced_graph: Vec<&mut [Vec<usize>]> = Vec::with_capacity(NTHREADS);
let ptr_graph = graph.as_mut_ptr();
// Creating mutable references for slices of the matrix
for n_th in 0..NTHREADS {
let offset = n_th * chunk;
let count_of_items = if offset + chunk > s_graph { s_graph - offset } else { chunk };
unsafe {
sliced_graph.push(slice::from_raw_parts_mut(ptr_graph.offset((offset) as isize),count_of_items));
}
}
thread::scope(|scope| {
for (n_th,slice) in sliced_graph.iter_mut().enumerate() {
scope.spawn(move |_| {
println!("thread number: {} - {:?}",n_th,slice);
for (row,r) in slice.into_iter().enumerate() {
for (col,cell) in r.into_iter().enumerate() {
println!("th:{} -->> set row:{} col:{}",row,col);
*cell = 1;
}
}
println!("thread number: {} - Finished!",n_th);
});
}
}).unwrap();
graph
}
fn main() {
build_graph();
}