Le jeudi 01 octobre 2015 à 06:46 -0700, Matt a écrit :
> Similar(x::Vector{Float64}) creates a new vector with NaN in some
> cases. There is no mention of this in the documentation. Is it a
> bug? It was a source of bug in my code since I was using something
> like scale!(x, 0) instead of fill!(x, 0) to define a general
> operation akin to BLAS gemm(\beta, A, B, \alpha, x) (where x may be
> a vector create by similar()).
> I can't reproduce such a behavior with simple vectors such as
> similar(randn(10000).
Actually, similar() here simply creates an uninitialized array, just
like calling Array(). Sometimes the memory contains only zeros, so
you'll get the impression that similar() returns arrays of zeros, but
it can also contain anything, including NaN or Inf. FWIW,
sum(similar(randn(1000))) frequently returns NaN here.
The fact that it sometimes returns NaN can actually be considered as a
nice feature, since it allowed you to find a bug. If it had returned
finite values, you may not even have noticed it.
There's currently a debate about always returning an array of zeros,
but no consensus has been reached yet:
https://github.com/JuliaLang/julia/issues/9147
Regards
> Here the command that fails:
>
> x =
> [93.9,95.4,98.5,96.4,95.5,88.4,90.1,89.8,95.4,101.1,102.9,108.2,111.7
> ,116.2,117.1,123.0,121.4,123.2,119.6,119.1,116.3,113.0,114.5,116.3,11
> 4.0,112.1,105.6,108.6,107.9,109.1,125.0,121.0,123.2,113.9,117.1,115.6
> ,113.8,115.2,109.6,125.0,128.3,133.1,121.8,122.3,121.7,124.7,124.6,12
> 6.8,113.8,113.5,111.1,107.1,107.1,107.9,106.1,102.2,96.8,88.9,81.2,79
> .0,103.4,102.6,100.3,98.9,102.9,104.0,102.9,100.3,104.1,103.9,108.0,1
> 09.7,114.8,119.1,122.6,127.3,126.5,131.8,128.7,127.4,128.0,123.1,125.
> 8,126.0,122.3,121.5,118.3,113.1,116.8,126.0,142.0,138.3,140.0,136.8,1
> 35.8,124.3,123.9,123.0,121.0,123.5,124.4,126.7,127.1,128.0,126.4,126.
> 1,121.9,120.2,118.6,115.4,110.8,104.8,102.8,99.7,97.5,90.1,82.4,77.8,
> 68.7,67.5,156.2,143.5,147.0,144.5,145.6,143.2,144.7,120.0,117.6,110.8
> ,109.3,112.4,110.2,113.4,117.3,117.5,117.4,118.0,116.4,114.7,114.1,11
> 2.5,111.0,108.5,109.0,104.8,100.6,91.5,86.7,83.6,165.8,170.9,170.8,16
> 1.3,158.2,164.8,175.5,155.0,161.1,156.3,154.7,151.3,147.6,153.0,153.3
> ,155.5,150.2,150.5,152.6,154.1,149.6,144.0,144.5,142.4,141.0,137.1,13
> 1.7,127.2,118.8,120.0,246.4,235.3,246.5,295.9,249.8,224.3,212.2,200.4
> ,213.0,220.6,209.4,182.7,176.5,167.7,136.7,130.3,128.5,129.7,131.9,13
> 2.0,124.5,124.6,122.1,117.2,113.0,105.4,101.1,84.1,82.2,82.6,137.5,12
> 5.5,131.1,131.3,132.8,129.3,121.2,123.6,123.0,126.0,132.6,136.0,131.9
> ,130.3,133.1,133.4,135.4,139.0,132.8,131.8,127.6,124.7,124.2,124.7,12
> 5.1,119.5,113.8,110.1,98.2,95.9,108.3,107.6,103.5,104.8,106.7,105.0,1
> 08.6,109.9,115.7,117.0,119.8,123.7,122.9,125.9,127.9,130.6,131.0,134.
> 0,131.7,131.2,128.6,126.3,128.8,129.0,129.3,124.1,117.1,113.8,109.6,1
> 09.2,97.0,90.1,95.2,94.5,98.3,99.1,100.6,102.4,108.5,126.1,121.8,125.
> 6,123.3,125.1,125.0,122.8,117.5,115.2,114.1,111.5,111.3,103.6,100.7,9
> 6.7,95.0,84.5,78.4,90.1,85.4,85.1,145.5,144.5,145.5,144.2,141.8,132.6
> ,130.4,124.8,125.6,126.6,124.4,131.9,131.8,134.4,134.0,136.7,135.3,13
> 5.2,133.0,130.7,127.9,124.0,121.6,118.2,109.5,107.6,104.6,94.1,96.1,9
> 4.8,138.5,134.3,135.3,132.1,134.8,134.3,132.9,134.6,139.3,149.2,156.0
> ,159.6,162.4,166.6,173.0,150.9,148.9,146.9,148.5,147.7,143.0,137.8,13
> 5.3,137.6,134.0,134.0,132.5,128.3,127.2,128.2,114.9,109.7,116.0,108.2
> ,113.7,109.2,107.9,108.5,108.4,109.4,110.6,116.1,120.5,124.4,125.5,12
> 7.1,124.2,124.6,132.9,116.2,115.6,111.2,109.4,104.1,101.1,100.2,94.4,
> 95.4,97.1,95.2,115.8,111.2,107.8,101.7,101.2,100.1,102.6,114.0,102.8,
> 111.0,115.2,118.6,123.4,127.7,127.9,127.1,126.4,127.1,132.0,130.9,127
> .6,121.7,115.7,109.4,105.2,103.2,96.5,94.3,91.8,90.0,126.3,127.0,128.
> 7,134.0,139.3,142.8,146.3,155.8,163.5,179.4,201.9,212.4,223.0,230.9,2
> 29.4,224.7,214.9,215.3,209.7,210.6,201.1,183.2,182.4,179.8,171.2,173.
> 2,171.6,182.5,170.8,167.6,114.0,114.0,117.5,119.7,120.0,117.3,115.9,1
> 15.9,119.8,125.3,126.7,129.9,133.6,139.6,140.0,142.7,140.1,143.8,144.
> 0,143.9,133.7,128.9,125.0,121.2,116.5,110.9,103.6,101.5,107.2,108.5,1
> 38.4,137.4,139.1,135.1,136.0,135.6,135.2,128.5,133.2,136.5,138.0,142.
> 1,140.7,144.9,145.6,143.9,138.5,141.2,138.9,139.5,135.4,135.5,127.9,1
> 19.0,125.0,125.0,122.4,117.5,116.1,114.7,122.7,122.2,121.0,121.0,121.
> 7,121.7,122.3,123.5,126.7,133.2,137.3,144.8,146.1,137.1,135.7,134.1,1
> 31.9,131.5,137.1,131.3,128.2,122.5,121.9,121.8,119.3,115.0,109.0,102.
> 8,97.6,91.7,142.2,138.7,136.5,131.6,130.2,128.0,129.7,124.3,121.4,117
> .9,121.2,124.3,126.1,116.9,118.9,120.5,118.2,120.5,123.2,122.3,119.8,
> 116.0,117.2,115.8,113.8,111.7,104.4,99.4,93.5,90.5,126.7,125.0,131.8,
> 134.5,134.4,134.2,133.4,128.6,126.1,131.4,133.7,138.8,136.8,138.0,140
> .3,141.8,140.9,140.7,139.5,137.3,128.3,128.2,126.6,126.5,122.1,121.1,
> 116.6,114.4,110.3,107.6,112.6,104.7,109.2,110.7,114.4,113.7,112.3,104
> .3,116.4,96.8,106.8,110.6,111.5,116.7,117.2,118.9,118.3,117.7,120.8,1
> 19.4,113.2,110.8,113.0,104.3,108.8,94.1,92.3,90.7,86.2,83.8,83.9,86.1
> ,83.5,86.9,88.1,89.0,91.0,93.4,105.4,112.1,115.0,117.1,116.8,120.9,12
> 2.1,124.9,123.9,127.0,125.3,125.8,122.3,116.4,115.3,113.2,110.0,109.0
> ,108.3,101.8,105.6,103.9,133.2,130.0,130.2,139.3,138.3,137.3,137.2,12
> 1.3,127.6,130.0,132.1,135.4,135.6,139.5,140.8,141.8,140.2,142.1,140.5
> ,139.7,134.1,130.0,129.2,128.8,128.7,127.4,122.8,119.1,119.9,122.3,11
> 8.9,112.8,118.0,114.9,118.0,116.1,117.4,111.2,115.6,122.2,119.9,121.9
> ,123.7,124.9,127.0,127.2,120.3,122.0,121.1,122.4,113.7,110.1,103.6,97
> .8,91.7,87.1,86.2,84.7,82.9,86.6,118.5,106.3,110.5,106.1,110.0,109.5,
> 108.4,108.1,108.6,104.9,106.6,110.5,114.1,118.1,117.7,117.4,116.1,116
> .3,117.0,117.1,110.8,107.7,105.1,103.1,101.3,92.9,93.8,89.9,92.4,90.6
> ,212.7,206.3,192.7,184.0,175.8,189.7,198.6,189.5,190.5,198.6,201.5,20
> 4.7,205.2,201.4,190.8,187.0,183.3,177.7,171.9,165.1,159.2,136.6,146.7
> ,142.6,147.7,141.9,137.9,137.3,115.5,110.0,221.4,223.9,233.8,287.6,29
> 7.9,264.0,248.5,265.7,278.0,296.2,279.0,269.8,269.1,290.5,278.8,269.6
> ,254.6,247.8,245.4,239.8,232.9,215.1,201.1,195.9,195.1,180.4,172.9,15
> 2.4,144.8,143.7,141.4,135.6,138.0,144.9,131.1,130.2,121.2,120.7,125.1
> ,128.4,120.2,121.4,122.3,122.4,122.8,123.9,123.8,124.3,127.9,126.3,12
> 1.3,117.8,116.9,115.5,111.6,107.8,103.0,98.6,86.7,86.6,92.5,89.9,96.3
> ,96.5,95.5,99.9,87.0,90.0,92.6,99.3,98.9,100.3,103.1,102.4,102.4,103.
> 1,101.0,102.7,103.0,97.5,96.3,88.9,88.0,88.2,82.3,77.7,74.4,70.8,69.9
> ,71.4,146.9,141.2,138.5,122.4,123.2,124.9,122.4,119.0,123.3,119.9,118
> .7,121.6,123.9,124.6,125.5,126.4,124.4,127.6,130.1,128.5,124.6,119.3,
> 115.9,114.0,108.9,106.2,100.1,93.7,86.4,82.4,103.3,102.0,103.2,99.5,9
> 6.3,97.0,96.9,93.8,98.5,103.8,108.7,110.5,117.9,125.4,122.2,121.9,121
> .3,123.7,125.7,126.8,119.6,109.4,103.2,99.8,92.3,87.1,84.1,77.1,85.2,
> 74.4,130.4,129.4,134.8,135.5,136.4,129.8,128.8,121.6,124.6,124.4,120.
> 5,122.1,122.5,124.6,127.3,131.3,130.9,133.5,132.8,134.0,130.0,127.1,1
> 26.7,126.3,124.6,122.4,118.6,115.5,113.2,112.3,113.4,111.5,115.6,115.
> 9,117.9,113.0,108.7,108.4,115.4,121.7,124.1,130.5,132.9,138.6,140.4,1
> 43.6,141.6,141.6,143.7,147.0,140.0,128.1,124.2,119.9,113.1,103.6,97.5
> ,88.4,87.8,86.3,128.3,117.4,120.4,122.9,125.5,117.1,114.7,107.3,106.3
> ,109.0,110.7,114.2,114.6,118.8,120.1,122.3,122.6,124.0,125.2,123.3,12
> 5.3,115.3,115.8,113.9,100.6,107.6,107.1,101.3,102.5,96.2,144.6,140.3,
> 133.2,140.2,144.5,142.9,117.8,123.9,123.2,134.4,142.0,146.1,154.7,150
> .2,148.8,146.8,145.8,149.3,151.2,146.3,135.8,136.9,133.4,136.3,124.4,
> 138.0,120.8,101.4,103.6,100.1,88.2,89.7,90.1,93.4,95.1,95.7,104.2,103
> .6,115.0,118.7,125.5,129.7,130.5,136.8,137.2,140.4,135.7,138.3,136.1,
> 136.0,131.1,127.0,125.4,126.6,126.6,124.4,122.4,118.6,121.5,121.9,106
> .0,99.4,98.7,98.8,99.6,100.4,102.5,92.7,96.7,103.0,103.5,108.4,113.5,
> 116.7,115.6,116.9,117.4,114.7,115.7,113.0,109.8,105.7,104.4,97.0,95.8
> ,91.9,87.4,88.3,91.8,93.0,110.3,105.5,108.1,109.9,111.5,109.2,107.3,9
> 9.8,106.3,111.5,109.7,114.8,117.4,121.7,124.6,127.3,127.2,130.4,129.1
> ,131.4,129.0,125.1,128.7,129.0,130.6,125.3,124.7,121.8,120.6,121.0,11
> 3.4,110.7,120.5,106.1,109.0,108.4,111.3,106.4,108.9,108.6,110.4,114.7
> ,116.0,121.4,124.2,126.6,126.4,129.7,129.0,131.2,126.4,117.2,115.9,11
> 3.7,105.8,96.5,94.5,85.6,79.6,77.2,72.0,62.3,65.0,65.7,64.3,64.3,65.6
> ,65.5,67.7,71.3,72.7,75.6,75.8,77.9,78.0,79.6,79.1,74.8,77.6,73.6,69.
> 0,66.3,66.5,64.4,67.7,55.0,57.0,53.4,53.5,55.0,133.5,129.1,122.9,130.
> 4,127.4,128.8,134.6,122.6,124.4,138.0,146.8,151.8,155.5,171.1,169.4,1
> 62.4,160.9,161.6,163.8,162.3,153.8,144.3,144.5,131.2,128.3,128.7,120.
> 9,124.3,120.9,126.5,122.8,118.5,123.3,120.2,120.9,122.8,123.9,124.3,1
> 28.4,137.0,143.1,149.6,152.7,158.1,157.7,155.9,151.8,148.9,149.9,147.
> 4,144.7,136.8,134.6,135.8,133.0,129.5,122.5,118.9,109.1,108.2,99.1,95
> .4,98.3,86.9,99.7,101.5,100.2,96.7,97.0,88.5,91.0,98.6,99.5,100.3,99.
> 3,101.3,101.4,101.4,112.7,106.6,102.4,96.2,96.5,94.2,91.3,88.2,86.1,8
> 3.4,78.7,81.1,111.8,109.0,110.5,111.2,113.6,119.8,112.1,114.5,111.5,1
> 17.5,116.6,119.9,123.2,129.7,133.9,131.6,122.1,122.3,120.5,119.8,115.
> 7,111.9,109.1,112.1,107.5,109.1,104.0,104.1,100.1,98.0,110.4,106.2,10
> 9.4,106.3,108.3,111.4,111.5,106.4,105.4,108.8,109.5,111.8,113.5,115.4
> ,117.2,116.7,117.1,117.6,119.9,115.6,106.3,105.6,107.0,105.4,106.0,10
> 2.6,100.3,94.1,95.5,96.2,125.6,134.0,137.6,133.3,137.4,136.5,135.7,13
> 2.2,131.7,140.0,141.2,145.8,160.7,161.5,160.4,160.3,168.6,158.1,163.1
> ,157.7,141.2,128.9,125.7,124.8,110.4,114.3,111.4,96.9,109.1,110.8];
> mean(x)
> mean(similar(x))
>
