taichi-dev/taichi

Reverse NDRange support

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#4,379 opened on Feb 24, 2022

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feature requestgood first issuewelcome contribution

Description

There comes one special case which requires a reverse loop, so I used “ti.ndrange(8,0)” instead. However, the reverse loop just didn’t work with zero warnings or errors (I have no idea whether ti.ndrange can be used to loop in reverse order at that time) Perhaps a warning message can be given when n1 > n2 in ti.ndrange((n1,n2))

import taichi as ti
ti.init(arch=ti.gpu, debug=True, default_fp=ti.f64)

x = ti.field(ti.f64, shape=(10))

@ti.kernel
def main():
    x[9] = 1.0
    for i in ti.ndrange((8,0)):
        x[i] = 2.0 * x[i+1]
        print(x[i])    #print nothing

main()

Contributor guide

Tech stack
pythoncpp
Domain
backenddeveloper experience
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
PythonTaichi basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
45
Research direction
Investigate the behavior of ti.ndrange when start > end. Currently it silently iterates zero times. Modify the Python frontend or the range validation logic to emit a warning when start > end. The change is likely in the Taichi Python frontend files like `taichi/lang/ndrange.py` or similar. After implementing, test with the provided example to ensure warning is printed.