develop

Resizing a image is not as easy as you think

I found a very interesting picture:

The size of this image is about 8MB although it’s blurring. Then I use below python code to try to resize it using different interpolation strategy:

import cv2

img = cv2.imread("/Users/robin/Downloads/ou1.png")

for inter, name in [(cv2.INTER_AREA, "area"), (cv2.INTER_CUBIC, "cubic"), (cv2.INTER_LINEAR, "linear")]:
    after = cv2.resize(img, (310, 310), inter)
    cv2.imwrite(f"{name}.bmp", after)

Only cv2.INTER_AREA works well.

Then let me try dart language:

import 'dart:io';
import 'package:image/image.dart' as img;

void main() async {
  // Load the image
  final file = File('/Users/robin/Downloads/ou1.png');
  final bytes = await file.readAsBytes();
  final image = img.decodeImage(bytes);

  if (image == null) {
    print("Failed to load image");
    return;
  }

  // Resize and save images with different methods
  for (var method in ['area', 'cubic', 'linear', 'average']) {
    img.Image resized;
    if (method == 'area' || method == 'linear') {
      // Use `copyResize` for these, `area` will behave similarly to default
      resized = img.copyResize(image, width: 310, height: 310);
    } else if (method == 'cubic') {
      // Simulate cubic interpolation (approximation)
      resized = img.copyResize(image, width: 310, height: 310, interpolation: img.Interpolation.cubic);
    } else if (method == 'average') {
      resized = img.copyResize(image, width: 310, height: 310, interpolation: img.Interpolation.average);
    } else {
      print("Unknown interpolation method: $method");
      continue;
    }

    // Save the resized image
    final output = File('$method.bmp');
    await output.writeAsBytes(img.encodePng(resized));
    print("Saved resized image using $method interpolation as $method.bmp");
  }
}

The result looks also terrible except just one strategy “average”:

So, better use “Interpolation.average” in dart language.

Fix the launching problem of Android Studio on Macbook

After I installed two versions of JDK (17 and 21) and uninstalled them, I saw this error when trying to launch my Android Studio. This error is hard to fix. Reinstalling Android Studio won’t fix it. And even after I searched google and asked chatGPT and try all the suggestion they give, the problem continued for two days.

The eventual solution is from a StackOverflow article (sorry I forget the url):

# firstly, manually uninstall Android Studio
# then
rm -rf /Library/Java/JavaVirtualMachines/*
# then
rm ~/Library/Application\ Support/Google/AndroidStudio*
# then
rm  -rf ~/Library/Caches/
# now install the Android Studio and it could be launched correctly

Strange problem in Python Client of Vertex AI

To create a pipeline schedule of Vertex AI, we can use below snippet:

from google.cloud import aiplatform

pipeline_job = aiplatform.PipelineJob(
  template_path="COMPILED_PIPELINE_PATH",
  pipeline_root="PIPELINE_ROOT_PATH",
  display_name="DISPLAY_NAME",
)

pipeline_job_schedule = pipeline_job.create_schedule(
  display_name="SCHEDULE_NAME",
  cron="TZ=CRON",
  max_concurrent_run_count=MAX_CONCURRENT_RUN_COUNT,
  max_run_count=MAX_RUN_COUNT,
  service_account="XYZ",
)

This Python code runs with service account “XYZ” and we also want the schedule to run as service account “XYZ”. Make sense, right? But the execution throws errors:

grpc._channel._InactiveRpcError: <_InactiveRpcError of RPC that terminated with:
	status = StatusCode.INVALID_ARGUMENT
	details = "You do not have permission to act as service_account: vertex-runner@pers-decision-engine-dev.iam.gserviceaccount.com. (or it may not exist)."
	debug_error_string = "UNKNOWN:Error received from peer ipv4:74.125.201.95:443 {created_time:"2024-06-06T01:51:02.837225888+00:00", grpc_status:3, grpc_message:"You do not have permission to act as service_account: vertex-runner@pers-decision-engine-dev.iam.gserviceaccount.com. (or it may not exist)."}"

Why does the Python Client of Vertex AI need to “act as” service account “XYZ” even if it’s already using default service account “XYZ”? I can’t answer. Fortunately, the solution is adding a role “Service Account User” to the service account “XYZ” (as this shows)

Seems Google Cloud still need to do a few works to let Vertex AI work very well.

“No space left on device” problem I met on ext4

After downloading the whole CC12M dataset from Huggingface, I wrote a tool to extract all of the image-text-pair files into one directory. But after extracting 17 million (17681010 exactly) files, the tool reported the error:

Exception: [Errno 28] No space left on device: '/home/robin/Downloads/cc12m/011647171.txt'

I checked the space and inodes in my ext4 filesystem, and seems they all have free capacity:

# "df -lh"
Filesystem      Size  Used Avail Use% Mounted on
tmpfs           3.2G  2.0M  3.2G   1% /run
/dev/nvme0n1p1  916G  410G  461G  48% /
tmpfs            16G  412K   16G   1% /dev/shm
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
efivarfs        192K  124K   64K  66% /sys/firmware/efi/efivars
/dev/sda2        96M   32M   65M  33% /boot/efi
tmpfs           3.2G   56K  3.2G   1% /run/user/1000
/dev/sdb2       3.7T  2.5T  1.3T  67% /mnt

# "df -i"
Filesystem       Inodes   IUsed    IFree IUse% Mounted on
tmpfs           4077303    1264  4076039    1% /run
/dev/nvme0n1p1 61054976 9308680 51746296   16% /
tmpfs           4077303     104  4077199    1% /dev/shm
tmpfs           4077303       4  4077299    1% /run/lock
efivarfs              0       0        0     - /sys/firmware/efi/efivars
/dev/sda2             0       0        0     - /boot/efi
tmpfs            815460      61   815399    1% /run/user/1000
/dev/sdb2             0       0        0     - /mnt

Then why the ext4 filesystem returned a “No space” error? The reason is explained here: https://blog.merovius.de/posts/2013-10-20-ext4-mysterious-no-space-left-on/.

After using “sudo dumpe2fs /dev/nvme0n1p1”, I got:

...
Journal inode:            8
Default directory hash:   half_md4
Directory Hash Seed:      e10f88a7-1d8c-4c38-a796-6fa15bdf4e65
...

Seems the hash algorithm of “index_dir” of my ext4 filesystem is already “half_md4” therefore my only choice is using “tea”. (The default “hash_algo” when you using “mke2fs” is “half_md4“)

But after I make the change:

sudo tune2fs -E "hash_alg=tea" /dev/nvme0n1p1

the error “No space left on device” still jumped out…

There are two solutions left:

Rewrite my tool to generate flat big files with every file contains previous “small files”
Replace ext4 with xfs (I will test this after I got another NVME SSD)

Simple Python code of Knapsack Problem

Just write this snippet for my practice of 0-1 Knapsack Problem:

values  = [1, 2, 3, 4, 5]
weights = [3, 2, 1, 9, 6]
max_weight = 12

def knappack():
    n = len(values)
    dp = [[0] * (max_weight+1) for _ in range(n)]
    print(dp)

    for i in range(n):
        for j in range(1, max_weight+1):
            if weights[i] > j:
                dp[i][j] = dp[i-1][j]
            else:
                dp[i][j] = max(dp[i-1][j], dp[i-1][j-weights[i]] + values[i])

    print(dp[-1][-1])

knappack()

An incorrect understanding of me for Skip-list

After reading the classic paper about Skip-list, I tried to implement it by myself. But then I found a line of pseudo-code in the “Delete” function that I couldn’t understand:

Seems all the elements in “update” will point to “x”, so why do we need to check here? Maybe I can ignore this checking. Now here comes a part of my code:

    def erase(self, num: int) -> bool:
        update = Node(-1)
        
        curr = self._head
        for level in range(MAX_LEVEL-1, -1, -1):
            while curr._forward[level] and curr._forward[level]._key < num:
                curr = curr._forward[level]
            update._forward[level] = curr
        
        curr = curr._forward[0]
        if curr == None or curr._key != num:
            return False
        curr._count -= 1
        if curr._count > 0:
            return True
        
        for level in range(MAX_LEVEL):
            update._forward[level]._forward[level] = curr._forward[level]
            
        del curr
        return True

But unfortunately, it failed for the test case. In the debugging process, I realized that not all elements in “update” will point to “x”. Le’ts just take the figure-1 from the paper as my example:

As above, imaging we are deleting node “17”. The “forward[1]” (index start from 0, this is the difference of my code with the paper) of node “9” is pointing to node “17” so it should be redirect to node “25”. But the “forward[3]” of node “6” is pointing to “NIL”, and shouldn’t be redirected to node “25” because “node6._forward[3]” didn’t point to node “17”. The situation is the same for “forward[4]” and beyond, of node “6”.

This is why the last few lines of my code should be:

......
        
        for level in range(MAX_LEVEL):
            if update._forward[level]._forward[level] != curr:
                break
            update._forward[level]._forward[level] = curr._forward[level]
            
        del curr
        return True

Just like the pseudo-code in the paper!

I am really respect to these academic guys — everytime I thought they were wrong is actually I missed something.

Extract only birds sound from audio

This paper introduced a method to extract only segments with bird sound from an audio file. Since the paper didn’t give any code, I started to write it by myself.

Here is the Python implementation:

import cv2
import time
import torch
import librosa
import soundfile as sf
import numpy as np

from torchlibrosa.stft import LogmelFilterBank, Spectrogram

class CFG:
    n_fft = 2048
    hop_length = 512
    sample_rate = 32000
    n_mels = 64
    fmin = 150
    fmax = 150000

class SignalExtractor:
    def __init__(self):
        self.spectrogram_extractor = Spectrogram(
            n_fft=CFG.n_fft, hop_length=CFG.hop_length, win_length=CFG.n_fft, window="hann",
            center=True, pad_mode="reflect", freeze_parameters=True)
        # Logmel feature extractor
        self.logmel_extractor = LogmelFilterBank(sr=CFG.sample_rate, n_fft=CFG.n_fft,
            n_mels=CFG.n_mels, fmin=CFG.fmin, fmax=CFG.fmax, ref=1.0, amin=1e-10, top_db=None, freeze_parameters=True)
        self.factors = [2.0, 1.8, 1.6, 1.4, 1.2, 1.1]
        self.kernel_size = 15
        self.sn_threshold = 0.2

    def extract(self, input):
        x = torch.from_numpy(input)
        x = x[None, :].float()

        x = self.spectrogram_extractor(x)
        x = self.logmel_extractor(x)

        x = x.squeeze(0).squeeze(0)
        x = x.permute(1, 0).numpy()
        x = x - np.amin(x)

        for factor in self.factors:
            sound, sn_ratio = self._factor_extract(input, x, factor)
            if sn_ratio >= self.sn_threshold:
                break

        return sound, sn_ratio

    def _factor_extract(self, input, x, factor: float):
        rows, cols = x.shape
        row_median = np.median(x, axis=1)
        row_median_matrix = np.tile(row_median, (cols, 1)).T * factor
        col_median = np.median(x, axis=0)
        col_median_matrix = np.tile(col_median, (rows, 1)) * factor

        y = x > row_median_matrix
        z = x > col_median_matrix
        res = np.logical_and(y, z) + np.zeros(x.shape)

        kernel = np.ones((self.kernel_size, self.kernel_size), np.uint8)
        img = cv2.dilate(res, kernel, iterations=1)

        indicator = np.sum(img, axis=0)
        chunk_size = input.shape[0] // indicator.shape[0]
        sounds = []
        for index, chunk in enumerate(indicator):
            if chunk > 0:
                sounds.append(input[index*chunk_size:(index+1)*chunk_size])
        if len(sounds) <= 0:
            return None, 0.0
        sound = np.concatenate(sounds)
        return sound, sound.shape[0]/input.shape[0]

The implementation has some differences from the method in the paper:

I didn’t use erosion since dilation is good enough for picking up the bird-sound segment
three times bigger than median is too strict for most audio files, so I use an array of ratios. When the 2.0 ratio couldn’t pick up any bird sound, the code will automatically try a 1.8 ratio etc.
I used a big kernel (15, 15) for dilation since it works well in my samples

The original sample:

After extracteing only bird sounds:

Intel extension for PyTorch

Trying to test the Intel extension for PyTorch in my project, but it reported errors:

Traceback (most recent call last):                                                                                                                                                                                                          
  File "reviewjpgs_optimaztion_testing.py", line 27, in <module>                                                                                                                                                                            
    import intel_extension_for_pytorch as ipex                                                                                                                                                                                              
  File "/home/hero/.pyenv/versions/3.8.12/lib/python3.8/site-packages/intel_extension_for_pytorch/__init__.py", line 11, in <module>                                                                                                        
    from .cpu import _cpu_isa                                                                                                                                                                                                               
  File "/home/hero/.pyenv/versions/3.8.12/lib/python3.8/site-packages/intel_extension_for_pytorch/cpu/__init__.py", line 1, in <module>                                                                                                     
    from . import runtime                                                                                                                                                                                                                   
  File "/home/hero/.pyenv/versions/3.8.12/lib/python3.8/site-packages/intel_extension_for_pytorch/cpu/runtime/__init__.py", line 3, in <module>                                                                                             
    from .multi_stream import MultiStreamModule, get_default_num_streams, \
  File "/home/hero/.pyenv/versions/3.8.12/lib/python3.8/site-packages/intel_extension_for_pytorch/cpu/runtime/multi_stream.py", line 4, in <module>
    import intel_extension_for_pytorch._C as core
ImportError: /home/hero/.pyenv/versions/3.8.12/lib/python3.8/site-packages/intel_extension_for_pytorch/lib/libintel-ext-pt-cpu.so: undefined symbol: _ZNK3c1010TensorImpl22is_strides_like_customENS_12MemoryFormatE

The answer is quite tricky: need to install the IPEX package with the same version of PyTorch.

After the testing of both torch.jit.trace and this IPEX, we found out that `torch.jit.trace` could boost the performance of prediction significantly but IPEX could not.

Empty messages received by PubSub pull()

I want my Python script to receive one message from a PubSub topic and then go on to other work. The code is learned from an example of the GCP document:

with subscriber:
    # The subscriber pulls a specific number of messages. The actual
    # number of messages pulled may be smaller than max_messages.
    response = subscriber.pull(
        request={"subscription": subscription_path, "max_messages": NUM_MESSAGES},
        retry=retry.Retry(deadline=300),
    )

    if len(response.received_messages) == 0:
        return

The problem is that it will receive empty messages, meaning that “len(response.received_messages)” is zero.

Where do these empty messages come from? Here is the answer:

Once a message is sent to a subscriber, the subscriber must either acknowledge or drop the message. A message is considered outstanding once it has been sent out for delivery and before a subscriber acknowledges it.

My solution is just to wait until receiving a non-empty message:

with subscriber:
    # The subscriber pulls a specific number of messages. The actual
    # number of messages pulled may be smaller than max_messages.
    while True:
      response = subscriber.pull(
          request={"subscription": subscription_path, "max_messages": NUM_MESSAGES},
          retry=retry.Retry(deadline=300),
      )

      if len(response.received_messages) > 0:
          break

Use bits instead of set for visited nodes. LeetCode #1434

My first idea is depth-first-search: iterate all people, try to give them different hats. The solution got TLE (Time Limit Exceeded). Then as a hint from discussion forum, I started to iterate hat (instead of people), try to give them different people. The solution also got TLE (even I used lru_cache for function):

from collections import defaultdict

class Solution:
        
    def numberWays(self, hats: List[List[int]]) -> int:
        hp = defaultdict(set)
        for index, hat in enumerate(hats):
            for _id in hat:
                hp[_id].add(index)
                
        hp = [people for people in hp.values()]
        @functools.lru_cache(None)
        def dfs(start, path) -> int:
            if len(path) == len(hats):
                return 1
            if start == len(hp):
                return 0
            total = 0
            for person in (hp[start] - set(path)):
                total += dfs(start + 1, tuple(list(path) + [person]))
            total += dfs(start + 1, path)
            return total % (10**9 + 7)

        return dfs(0, tuple())

Using list as data structure to record visited node is not efficient enough in this case. Since there will be no more than 10 people, the most efficient data structure to record visited people is bits.

My final solution is still using dfs (by using lru_cache, it is also a dynamic-programming):

from collections import defaultdict

class Solution:
        
    def numberWays(self, hats: List[List[int]]) -> int:
        hp = defaultdict(set)
        for index, hat in enumerate(hats):
            for _id in hat:
                hp[_id].add(index)
                
        hp = [people for people in hp.values()]
        @functools.lru_cache(None)
        def dfs(start, mask) -> int:
            if bin(mask).count('1') == len(hats):
                return 1
            if start == len(hp):
                return 0
            total = 0
            for person in hp[start]:
                if (1 << person) & mask > 0:
                    continue
                mask |= 1 << person
                total += dfs(start + 1, mask)
                mask ^= 1 << person
            total += dfs(start + 1, mask)
            return total % (10**9 + 7)

        return dfs(0, 0)

“area”	“cubic”	“linear”	“average”