ndrs 0.3.0

A tensor library with GPU support
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//! 广播形状计算

pub fn broadcast_shapes(shape1: &[usize], shape2: &[usize]) -> Option<Vec<usize>> {
    let mut result = Vec::new();
    let len1 = shape1.len();
    let len2 = shape2.len();
    let max_len = std::cmp::max(len1, len2);
    for i in 0..max_len {
        let dim1 = if i < len1 { shape1[len1 - 1 - i] } else { 1 };
        let dim2 = if i < len2 { shape2[len2 - 1 - i] } else { 1 };
        if dim1 == dim2 || dim1 == 1 || dim2 == 1 {
            result.push(std::cmp::max(dim1, dim2));
        } else {
            return None;
        }
    }
    result.reverse();
    Some(result)
}

#[cfg(test)]
mod tests {
    use super::broadcast_shapes;

    #[test]
    fn test_broadcast_shapes() {
        let a = vec![3, 1];
        let b = vec![1, 4];
        let result = broadcast_shapes(&a, &b).unwrap();
        assert_eq!(result, vec![3, 4]);

        let a = vec![2, 3];
        let b = vec![3];
        let result = broadcast_shapes(&a, &b).unwrap();
        assert_eq!(result, vec![2, 3]);

        let a = vec![2];
        let b = vec![3];
        assert!(broadcast_shapes(&a, &b).is_none());
    }
}